Terrain and Scenery

Table of Contents

Overview

The terrain system in Flight Simulator consists of eight main data components, elevation (DEM data), imagery, land classification, water classification, regions, seasons, population density, and vector data. All sets of data can be replaced in whole or in part by new data, perhaps providing a higher resolution, or sometimes simply alternative data. The main tasks that are covered by this document are:

The Terrain System

The terrain system in Flight Simulator is optimized to minimize disk space. Whereas it would be technically possible to create the entire world from satellite imagery and high resolution elevation data, this would involve an enormous amount of data and is still not a practicable proposition, even with the huge storage space available on DVDs. Because of this, it is possible to improve on Flight Simulator's terrain and scenery in specific local areas. Before going into how to make these improvments in detail, this section describes how the system functions by default.

The key to the terrain system is a grid, where the World is divided into squares, roughly 1.2km on each side. Using this concept, information is held on the World for the following properties: geographical region, population density, land classification, water classification and season. For example, if an aircraft is  flying over one of these grid squares in North America, this information can be used not only to build a good approximation of the terrain, but also provide information on how busy the highways are likely to be. At exactly the same simulated time, an aircraft flying in the sourthern hemisphere may well be flying in a different season, and even though the land classification may be identical to the grid square in North America, the rendering of that land can be different because of regional variations in what trees make up a forest, or shrub is present on a desert, for example. The grid system is not used for actual terrain imagery or elevations, but as reference information so that the correct textures can be located for any area.

The following image shows the land classification for the sourthern tip of Vancouver Island, Seattle, and some of the Cascade mountains. The 1.2km squares are very evident in the data. To view the default data, run the TmfViewer.exe tool. Using this tool you can examine the BGL files that contain the default grid data.

 

 

Regions

The following diagram shows the geographical regions the world is divided into.

The regions are:

Note that Antartica and the interior of Iceland are classified as Artic, but the coastline of Iceland falls into the Europe Germanic category.

Using TmfViewer first load in the image of the world - stored in the Microsoft Flight Simulator X\Scenery\World\Scenery folder.This can be used as a background image with other information appearing as overlays.

 

Next, from the Microsoft Flight Simulator X\Scenery\Base\Scenery folder, load in the regions.bgl file. This will show the regions overlayed onto the world map, as follows:

To zoom in on a particular area of the world, first just click the mouse on the area of interest, then press the Numpad + key to zoom in (or Numpad - to zoom out). For example, to examine the center of Australia in more detail, click on the red region in the center, then press Numpad + a few times, and you should get the following image:

It is possible to change the regions that have been applied to the world, though it is not possible to add new regions to the 24 listed above.

Land Classification

Next load up TmfViewer again, this time with just the worldlc.bgl file, in the Microsoft Flight Simulator X\Scenery\Base\Scenery folder. This contains all the land classification data.

Each color coded square in the grid corresponds with a single land type from the Olson Land Classification Table, shown below. It is not possible to provide a greater degree of resolution than the 1.2km squares of the grid, it is possible to change the land classification to a different value from the table. 

Olson Land Classification Table

For any square on the land classification grid, a single value from the following table applies.

Value
Land Classification Description
0 Ocean, Sea, Large Lake
1 Large City Urban Grid Wet
2 Low Sparse Grassland
3 Coniferous Forest
4 Deciduous Conifer Forest
5 Deciduous Broadleaf Forest
6 Evergreen Broadleaf Forests
7 Tall Grasses And Shrubs
8 Bare Desert
9 Upland Tundra
10 Irrigated Grassland
11 Semi Desert
12 Dry Crop and Town
13 Wooded Wet Swamp
14 ### Unused ###
15 ### Unused ###
16 Shrub Evergreen
17 Shrub Deciduous
18 ### Unused ###
19 Evergreen Forest And Fields
20 Cool Rain Forest
21 Conifer Boreal Forest
22 Cool Conifer Forest
23 Cool Mixed Forest
24 Mixed Forest
25 Cool Broadleaf Forest
26 Southern Deciduous Broadleaf Forest
27 Conifer Forest
28 Montane Tropical Forests
29 Seasonal Tropical Forest
30 Cool Crops And Towns
31 Crops And Town
32 Dry Tropical Woods
33 Tropical Rainforest
34 Tropical Degraded Forest
35 Corn And Beans Cropland
36 Rice Paddy And Field
37 Hot Irrigated Cropland
38 Cool Irrigated Cropland
39 ### Unused ###
40 Cool Grasses And Shrubs
41 Hot And Mild Grasses And Shrubs
42 Cold Grassland
43 Savanna (Woods)
44 Mire Bog Fen
45 Marsh Wetland
46 Mediterranean Scrub
47 Dry Woody Scrub
48 Dry Evergreen Woods
49 ### Unused ###
50 Sand Desert
51 Semi Desert Shrubs
52 Semi Desert Sage
53 Barren Tundra
54 Cool Southern Hemisphere Mixed Forests
55 Cool Fields And Woods
56 Forest And Field
57 Cool Forest And Field
58 Fields And Woody Savanna
59 Succulent And Thorn Scrub
60 Small Leaf Mixed Woods
61 Deciduous And Mixed Boreal Forest
62 Narrow Conifers
63 Wooded Tundra
64 Heath Scrub
65 ### Unused ###
66 ### Unused ###
67 ### Unused ###
68 ### Unused ###
69 Polar And Alpine Desert
70 ### Unused ###
71 ### Unused ###
72 Mangrove
73 ### Unused ###
74 ### Unused ###
75 ### Unused ###
76 Crop And Water Mixtures
77 ### Unused ###
78 Southern Hemisphere Mixed Forest
79 ### Unused ###
80 ### Unused ###
81 ### Unused ###
82 ### Unused ###
83 ### Unused ###
84 ### Unused ###
85 ### Unused ###
86 ### Unused ###
87 ### Unused ###
88 ### Unused ###
89 Moist Eucalyptus
90 Rain Green Tropical Forest
91 Woody Savanna
92 Broadleaf Crops
93 Grass Crops
94 Crops Grass Shrubs
95 Grass Skirting 1
96 Grass Skirting 2
97 Grass and Shrub Skirting
98 Dry Grass and Dirt Skirting
99 Sand and Desert Skirting
100 Ocean, Sea, Large Lake
101 Large City Urban Grid Wet
102 Large City Urban Grid Dry
103 Large City Urban Non Grid Wet
104 Large City Urban Non Grid Dry
105 Medium City Urban Grid Wet
106 Medium City Urban Grid Dry
107 Medium City Urban Non Grid Wet
108 Medium City Urban Non Grid Dry
109 Large City Suburban Grid Wet
110 Large City Suburban Grid Dry
111 Large City Suburban Non Grid Wet
112 Large City Suburban Non Grid Dry
113 Medium City Suburban Grid Wet
114 Medium City Suburban Grid Dry
115 Medium City Suburban Non Grid Wet
116 Medium City Suburban Non Grid Dry
117 Small City Suburban Grid Wet
118 Small City Suburban Grid Dry
119 Small City Suburban Non Grid Wet
120 Small City Suburban Non Grid Dry
121 Large City Highrise
122 Ice
123 Inland Water
124 Ocean Inlet
125 Non Perennial Inland Water
126 Non Perennial Inland Sea
127 Reef
128 Grass
129 Arid
130 Rock
131 Dirt
132 Coral
133 Lava
134 Park
135 Golf Course
136 Cement
137 Tan Sand Beach
138 Black Sand Beach
139 Airfield1
140 Airfield2
141 Rock Volcanic
142 Rock Ice
143 Glacier Ice
144 Evergreen Tree Crop
145 Deciduous Tree Crop
146 Desert Rock
147 Savanna Grass

 

Use TmfViewer to zoom in on  the area around San Diego. Notice that if you place the mouse over any grid square the Olson class value is given, along with the latitude and longitude, for that square. Although classifications are color coded within the tool, this method of placing the mouse and reading the value is the most precise way of determining land class values.

Elevations

To draw the landscape, elevation data is held in the dem4km.bgl file, also in the Microsoft Flight Simulator X\Scenery\Base\Scenery folder. For Flight Simulator X, higher resoultion elevation data is provided than for Flight Simulator 2004. See the section on Base File Information for details on where this elevation data is stored. And compare the lower and higher resolution elevation data for Hawaii below.


The following image shows the old elevation data for Hawaii, note the value given in the information bar is 3904. This is the height in meters of the square the mouse is pointing at.

The higher resolution elevation data for Hawaii provides the following image.


Seasons

There are five seasons: Spring (SP), Summer (SU), Fall (FA), Winter (WI), and Hard Winter (HW). The main difference between the two winter textures, WI and HW, is the snow on the ground in Hard Winter. Seasons are different across the world at any one time, and this information is held by Flight Simulator for the 12 months of the year. Seasonal information does not vary at all in the simulation within a month, and changes on midnight at the end of the month to the new season. The following table shows the season information for four months of the year. Note that green identifies summer, yellow is spring, red is fall, grey is mild winter, and white is hard winter.

 

January
April
July
October

To view the season information using TmfViewer, first load up the image_globe.bgl file from Microsoft Flight Simulator X\Scenery\World\Scenery. Note that the first image loaded into this tool is always opaque. The next images loaded can be drawn transparent, so the outline of the countries/regions and continents shows through.

Next load up the seasons.bgl file from Microsoft Flight Simulator X\Scenery\Base\Scenery. Use the View menu to select the various months of the year.


Water Classification

There is not the same broad range of types and variants present in the water classes that are found in the land textures. By default, water classes use one region and have one season, one variation, and no night texture. To give greater visual control, water is categorized by depth, plankton concentration, and whether it is tropical. The depth tends to dictate the darkness of the water color: the deeper the water, the darker the texture. The plankton concentration determines the amount of green in the water color:  the more plankton, the greener the water. Tropical waters are highlighted because they tend to have a more vibrant color. Load up worldwc.bgl to see the water classification map:

The following definitions are used for water depth:


Texture  Number
Water Texture Description
1 Shallow Inland Water–Blue
2 Deep Inland Water–Blue
3 Ocean Inlets–Blue
4 Non Perennial Inland Sea–Blue
5 Non Perennial Inland Water–Blue
6 Outflow Water – Blue
   
7 Shallow Inland Water–Brown
8 Deep Inland Water–Brown
9 Ocean Inlets––Brown
10 Non Perennial Inland Sea–Brown
11 Non Perennial Inland Water–Brown
12 Outflow Water–Brown
   
13 Shallow Ocean Water 1–Class1 (High Plankton Concentration)
14 Shallow Ocean Water 2–Class1 (High Plankton Concentration)
15 Shallow Ocean Water 3–Class1 (High Plankton Concentration)
16 Shallow Ocean Water 4–Class1 (High Plankton Concentration)
17 Medium Depth Ocean Water–Class1 (High Plankton Concentration)
18 Deep Ocean Water–Class1 (High Plankton Concentration)
   
19 Shallow Ocean Water 1–Class2 ( Med High Plankton Concentration)
20 Shallow Ocean Water 2–Class2 ( Med High Plankton Concentration)
21 Shallow Ocean Water 3–Class2 ( Med High Plankton Concentration)
22 Shallow Ocean Water 4–Class2 ( Med High Plankton Concentration)
23 Medium Depth Ocean Water–Class2 ( Med High Plankton Concentration)
24 Deep Ocean Water –Class2 (Med High Plankton Concentration)
   
25 Shallow Ocean Water 1–Class3 (Med Low Plankton Concentration)
26 Shallow Ocean Water 2–Class3 (Med Low Plankton Concentration)
27 Shallow Ocean Water 3–Class3 (Med Low Plankton Concentration)
28 Shallow Ocean Water 4–Class3 (Med Low Plankton Concentration)
29 Medium Depth Ocean Water–Class3 (Med Low Plankton Concentration)
30 Deep Ocean Water –Class3 (Med Low Plankton Concentration)
   
31 Shallow Ocean Water 1–Class4 (Low Plankton Concentration)
32 Shallow Ocean Water 2–Class4 (Low Plankton Concentration)
33 Shallow Ocean Water 3–Class4 (Low Plankton Concentration)
34 Shallow Ocean Water 4–Class4 (Low Plankton Concentration)
35 Medium Depth Ocean Water–Class4 (Low Plankton Concentration)
36 Deep Ocean Water –Class4 (Low Plankton Concentration)
   
37 Shallow Ocean Water 1–Class1 (High Plankton Concentration), Tropical
38 Shallow Ocean Water 2–Class1 (High Plankton Concentration), Tropical
39 Shallow Ocean Water 3–Class1 (High Plankton Concentration), Tropical
40 Shallow Ocean Water 4–Class1 (High Plankton Concentration),Tropical
41 Medium Depth Ocean Water–Class1 (High Plankton Concentration), Tropical
42 Deep Ocean Water –Class1 (High Plankton Concentration), Tropical
   
43 Shallow Ocean Water 1–Class2 ( Med High Plankton Concentration), Tropical
44 Shallow Ocean Water 2–Class2 ( Med High Plankton Concentration), Tropical
45 Shallow Ocean Water 3–Class2 ( Med High Plankton Concentration), Tropical
46 Shallow Ocean Water 4–Class2 ( Med High Plankton Concentration), Tropical
47 Medium Depth Ocean Water–Class2 ( Med High Plankton Concentration), Tropical
48 Deep Ocean Water –Class2 (Med High Plankton Concentration), Tropical
   
49 Shallow Ocean Water 1–Class3 (Med Low Plankton Concentration), Tropical
50 Shallow Ocean Water 2–Class3 (Med Low Plankton Concentration), Tropical
51 Shallow Ocean Water 3–Class3 (Med Low Plankton Concentration), Tropical
52 Shallow Ocean Water 4–Class3 (Med Low Plankton Concentration), Tropical
53 Medium Depth Ocean Water–Class3 (Med Low Plankton Concentration), Tropical
54 Deep Ocean Water –Class3 (Med Low Plankton Concentration), Tropical
   
55 Shallow Ocean Water 1–Class4 (Low Plankton Concentration), Tropical
56 Shallow Ocean Water 2–Class4 (Low Plankton Concentration), Tropical
57 Shallow Ocean Water 3–Class4 (Low Plankton Concentration), Tropical
58 Shallow Ocean Water 4–Class4 (Low Plankton Concentration), Tropical
59 Medium Depth Ocean Water–Class4 (Low Plankton Concentration), Tropical
60 Deep Ocean Water –Class4 (Low Plankton Concentration), Tropical

The following image shows a close up of the Gulf of Mexico, the light green areas clearly denoting the Shallow Inland Water classifications.


Population Density

The population density of an area helps provide some guidelines as to the amount of traffic that is on the highways, recreational boat traffic on lakes, train frequency, and so on. Population density is held in values from 0 (no people) to 100 (very high density city). Note that black, used to identify the zero population case, occurs in several land locations in the map below.

 

The following image shows the population density map for some of the northeast coast of the United States. The very high concentrations around the cities of Boston, New York and Philadelphia are very evident.

Base File Information

The file system used to store all the terrain information is based around the following grid. In Microsoft Flight Simulator X\Scenery you will notice many folders with numeric names such as 0000, 1107, and so on. The first two numbers refer to the column of data (from 00 to 11) and the second two to the row of data (from 00 to 07). So 0000 contains the default information for the top left hand rectangle in the diagram below, and 1107 the information for the bottom right hand rectangle. Each of the larger rectangles (shown in red) is divided into smaller rectangles (shown in blue).

 

There are 8 x 8 smaller rectangles within each larger one. These smaller rectangles reference scenery and vector data that is present within that area. These are also numbered column first, then row, so the small grid square 7824, for example, is the area around Hong Kong SAR (which falls in the large grid square 0903). This is a different grid system than the 1.2Km squares used previously. This system is used to organize the data files in a reasonably logical way. The large grid squares represent QMID level 4, the smaller squares QMID level 7 (see QMID and LOD values for more details).

If you take, for example, the folder 0303, this will contain data for much of the Caribbean Sea. Use TmfViewer to open the dem0303.bgl file in this folder, and you will see the following high resolution elevation data image. Each of the numbered directories will contain elevation data with demNNNN in the filename. This higher resolution data is used to draw the landscape more accurately when using Flight Simulator X when compared with the previous version, Flight Simulator 2004. See the Elevations section for a comparison of lower and higher resolution images of Hawaii.

 

TmfViewer can also be used to examine the vector data (roads, rivers, streams and so on) for an area of the above grid. For example, open the file cvx7824.bgl (in the folder scenery/0903/scenery). Use the + key to zoom in and you will see the following vector data applies to the area around Hong Kong SAR. Clearly the red lines are major highways, the blue lines are streams, the grey lines are utilities, the yellow areas are airport boundaries and the green areas are parks. Right click near a vector to be given the option Identify Vector Features, which can be used to give details on the type of the vector.

The Shp2Vec Tool

The Shp2Vec (shape file to vector data) tool is in the SDK\Environment Kit\Terrain SDK folder. This tool takes vector shape data and creates the BG:L files used by Flight Simulator. The vector shape data is in standard ESRI shape file format. This format includes three file types, .shp (shape data), shx (shape index data), and .dbf (database file containing attributes of the shape data). Shape file viewing utilities are available for free from a number of websites. The format is documented in the following paper:

 

http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf

 

The Shp2Vec tool is command line driven, and takes the following parameters:

 

>Shp2Vec path quad -flags

 

The path points to the root folder containing all the shape data. All shape files in that folder, or any sub-folder, are examined by the tool if the filename contains the quad number. The quad numbers can be located in the Base File Information grid (for example, Hong Kong SAR is in the quad 78 24). The tool simply looks for files with the quad string present in the name, these strings do not have to match the grid squares, but can be any string that is common to all the shape vector filenames.

 

The default behavior of the tool is to provide replacement data for the quad cell. The flag -ADDTOCELLS is optional, and simply indicates the new data should be merged with existing data, and not replace it.

 

In addition to the shape files there is a propietary XML file that provides GUIDs of the appropriate vectors and textures that are used by Flight Simulator. The table below links to typical XML files, which are all used in Shp2Vec Example 1, except the Exclusions vector data, which is used in Shp2Vec Example 2.

 

Vector Data
Example
Notes
Airport Boundaries FLX7824 Airport boundaries are used for a number of purposes, including flattening the surface. Flight Simulator X does not support sloped runways.
Slopes and medium/high resolution water polygons HPX7824  
Streams STX7824 Includes rivers.
Low resolution water polygons HGX7824 These are used for GPS systems.
Roads RDX7824 This provides the graphic and data for the road surface. To have moving traffic appear on the road, a corresponding Freeways entry must be made. There is a significant performance cost in rendering moving road traffic.
Freeways FWX7824 This indicates moving traffic is drawn. There is no road surface associated with this type. Note that where freeways merge into a smaller number of lanes, the traffic on the dropped lanes simply disappears.
Utilities UTX7824 Includes power lines, telephone lines, and similar data.
Shorelines HLX7824 Shorelines in this context are those where a breaking wave (surf) effect should appear. Shoreline vectors are directional polylines that must go clockwise around the water polygons.
Railways RRX7824  
Parks PKX7824  
Exclusions  

Exclusions are polygons that exclude other shapes whose bounding boxes overlap the bounding box of the exclusion polygon. The use of bounding boxes is less precise than using the actual shape geometry, but it's much faster at run time. Exclusions only apply to shapes that are in lower priority scenery layers in scenery.cfg. You cannot exclude shapes in the same or higher priority scenery layers.

Exclusion polygons have a Texture attribute GUID like all the other terrain vector data and it is used to determine what type of shapes should be excluded. There are three options for what to exclude:

1. Exclude everything by using a NULL Texture GUID (all zeros).

2. Exclude general classes of shapes (for example, all roads or all water polygons) by using one of the GUIDs from the Vector Attributes table.

3. Exclude specific types of shapes (for example, only one lane gravel roads or only golf course polygons) by using one of the GUIDs listed in VectorShapePropertiesGuids. Note that you will have to convert the GUID from a C++ format to the XML format.

Notes

Vector Attributes

The following table gives the GUIDs that apply for each type of vector data. Refer to the example XML files on how they are used.

 

Attribute Set
Output Column
CLIP LEVEL
COMMENT
ATTRIBUTE BLOCK
ATTRIBUTEBLOCKGUID
AirportBounds   11 This uses 3D vertices, there is no special attribute to indicate this. AirportBounds {359C73E8-06BE-4FB2-ABCB-EC942F7761D0}
AirportBounds Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
AirportBounds Uuid 11 Unique ID (does not go into game) AirportBounds {359C73E8-06BE-4FB2-ABCB-EC942F7761D0}
Exclusions Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
Exclusions Uuid 11 Unique ID (does not go into game) Exclusions {AC39CDCB-DB78-4628-9A7C-051DA7AC864A}
FreewayTrafficRoads NumberOfLa 15 Note the dbf file format truncates the Output Column type to 10 characters. The number of lanes can be in the range 1 to 9. Guid of texture (as text) FreewayTrafficRoads {54B91ED8-BC02-41B7-8C3B-2B8449FF85EC}
FreewayTrafficRoads TrafficDir 15

The direction of the traffic is specified in the shape file

‘B’ = both directions

‘F’ = from reference node (one direction, cars drive away from vertex 0 toward vertex N)

‘T’ = toward reference node

 FreewayTrafficRoads {54B91ED8-BC02-41B7-8C3B-2B8449FF85EC}
FreewayTrafficRoads Uuid 15 Unique ID (does not go into game) FreewayTrafficRoads {54B91ED8-BC02-41B7-8C3B-2B8449FF85EC}
Parks Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
Parks Uuid 11 Unique ID (does not go into game) Parks {91CB4A9B-9398-48E6-81DA-70AEA3295914}
Railways Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
Railways Uuid 11 Unique ID (does not go into game) Railways {33239EB4-D2B8-46F5-98AB-47B3D0922E2A}
Roads Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
Roads Uuid 11 Unique ID (does not go into game) Roads {560FA8E6-723D-407D-B730-AE08039102A5}
Shorelines Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
Shorelines Uuid 11 Unique ID (does not go into game) Shorelines {0CBC8FAD-DF73-40A1-AD2B-FE62F8004F6F}
Streams Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
Streams Uuid 11 Unique ID (does not go into game) Streams {714BF912-F9DF-467E-80AE-28EB27374DBD}
Utilities Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
Utilities Uuid 11 Unique ID (does not go into game) Utilities {C7ACE4AE-871D-4938-8BDC-BB29C4BBF4E3}
WaterPolys   11 This uses 3D vertices, there is no special attribute to indicate this. WaterPolys {956A42AD-EC8A-41BE-B7CB-C68B5FF1727E}
WaterPolys Guid 11 Guid of texture (as text) Texture {1B6A15BB-05FB-4401-A8D1-BB520E84904C}
WaterPolys SlopeX 11 Slope in vertical meters per degree of longitude. 13 char floating point number. Slope {CEB07D86-3605-44BE-B48A-97F8D01B74DE}
WaterPolys SlopeY 11 Slope in vertical meters per degree of latitude. 13 char floating point number. Slope {CEB07D86-3605-44BE-B48A-97F8D01B74DE}
WaterPolys Uuid 11 Unique ID (does not go into game) WaterPolys {956A42AD-EC8A-41BE-B7CB-C68B5FF1727E}
WaterPolysGPS Uuid 11 Unique ID (does not go into game) WaterPolysGPS {EA0C44F7-01DE-4D10-97EB-FB5510EB7B72}

 

Notes

Shp2Vec Example 1: Hong Kong SAR Area

The Vector Examples/Example1/SourceData folder includes all the files for all the types of vector data present around Hong Kong SAR. To run the example type the following in the command line, after navigating to the SDK\Environment Kit\Terrain SDK folder.

 

>shp2vec "Vector Examples\Example1\SourceData" 7824

 

The BGL file will be written to the same folder as the data, an example of the output is in the Vector Examples/Example1/Output folder. The command-line output will give some statistics when the tool runs correctly, for example the output from running the tool with the above example data is shown below:

 

 

Shp2Vec Example 2: Excluding and Replacing around Hong Kong SAR (VHHH).

The Vector Examples/Example2/SourceData folder includes an example excluding and then replacing AirportBounds geometry around Hong Kong SAR. To run the example type the following in the command line, after navigating to the SDK\Environment Kit\Terrain SDK folder.

 

>shp2vec "Vector Examples\Example2\SourceData" VHHH -ADDTOCELLS

Note the importance of the -ADDTOCELLS flag to add this data to the existing vector data. In the TmfViewer tool, the new airport boundary is shown in the following image.

 

 

The TmfViewer Tool

The TmfViewer tool is in the SDK\Environment Kit\Terrain SDK folder. It can be used to examine many different types of data stored in BGL files. You cannot use this tool to examine all BGL files, however, just those using the World grid system. 

 

Use the File/Open menu item to load a file. Use the Jump menu items to save and use selected map locations. The following table describes the View menu elements of the TmfViewer tool.

Menu item
Description
Level of Detail All the available levels of detail (LOD) contained in the BGL file will be enabled. If an image is loaded and nothing appears, it can be that the Level of Detail is not set to a value that is applicable. Refer to QMID and LOD values for more details.
LOD Grid Draws a grid showing the sizes of the LOD cells. Refer to QMID and LOD values for more details.
QMID Grid Draws a grid showing the sizes of the QMID cells. Refer to QMID and LOD values for more details.
Seasons/Variations If seasonal data is relevant for the BGL file, then the months of the year, and the Night item will be enabled if they are present.
Show Missing Data Mask Selecting this will highlight any areas of data that are missing (that match the NullValue value, refer to the Source Parameters for .inf files more details) with a blue/gray shading.
Show Water Mask Water on a land texture is determined by the alpha channel. Selecting this item will display such areas in blue.
Highlight Values ... This enables all areas with the same data value to be highlighted. For example, if Land Classification data is being examined, and the Land Class highlight value is set to 16 (see the Olson Land Classification table), then all the Shrub Evergeen areas will be highlighted (in bright purple). Highlighting can also be done by right-clicking on an area. All otther areas with the same data value will be highlighted.
Clear All Highlights Simply resets all the Highlight Values to -1 (no highlights).
Elevation Color Ramp... The elevation colors are fixed: magenta (lowest elevation), violet, blue, green, yellow, red,, white (highest). Changing the color ramp values changes at what elevation the colors change.
Overlay transparency... The first file loaded by this tool is always drawn opaque. Select this item if subsequent files loaded should be drawn transparent, so the first file shows through. This can be useful when comparing world elevation data, with the world population density, for example.
Vector Data Vector Data is linear data such as roads, streams, utility lines, shorelines, and other similar features. When vector data is loaded into this tool, select which data items that should be displayed.
Zoom Zoom in and out. This can also be done with the Numpad + and Numpad - keys.
Pan Pan North, South, East and West. This can also be done with the up, down, right and left arrow keys.

The Resample Tool

The key process in replacing or modifying the default data is known as resampling, and the key tool for this process is the resample.exe tool. This is a command line driven tool that takes information from a text file (a .inf file) and then processes the files referenced according to the parameters set. The following section describes the parameters that can be set in an .inf file, and this is followed by a number of worked examples.

 

The following are the four basic steps required to replace default data in Flight Simulator X.

  1. Acquire raw digital data (see the Resample Examples for some suggestions).
  2. Create an .inf file for the raw data.
  3. Run Resample.exe on the raw data to create a .bgl file.
  4. Place the new files in the right folders for Flight Simulator.

The resample tool is in the SDK\Environment Kit\Terrain SDK folder. The simplest way to use it is to drag a single .inf file onto the Resample tool icon. This is equivlant to a call in the command line: Resample file.inf. To run Resample tool from the command line allows a few options and the use of multiple .inf files, with the following format:


Resample [-i, -q, ?] file1.INF[file2.INF…fileN.INF]

All .inf files are text files with at least two sections:

By default, the resampler scans each .inf file, collecting information from each [Source] section it encounters. Once a [Destination] section is found, it proceeds with the resampling process. If more [Source] sections are thereafter encountered, they are treated as a separate task and these sections will be used when the next [Destination] section is encountered. If the -i switch is specified, resample ignores all but the last [Destination] section, so considers the whole file as a single task.

Multiple .inf files are allowed because it is possible for the [Source] and [Destination] sections to be in separate files. This is convenient when you want to generate different resolutions of data from a single source file. Build an .inf file for the source data and multiple .inf files with [Destination] sections for each destination file. To generate one destination file from multiple source files, create an .inf file with a [Source] section for each file and a .inf file with a [Destination] section and list them all on the command line with the destination .inf file listed last.

 

Comments

To add a comment to an .inf file, either a whole line or information at the end of a line, add a semi-colon, this indicates to the Resample tool that any text following the semi-colon on the same line be ignored.

Source Parameters

If the file contains multiple source files, then the following section needs to be added to the top of the file (it has an identical [Source] directive to the parameters for a single file). All parameters are of the form Parameter = Value. There can be spaces or tabs either side of the equals sign.

 

[Source] section

It is possible to define more than one source image in a single .inf file.  This is extremely useful when working with imagery that has seasonal and night time variations.  To define multiple source images, set the value of the [Source] Type directive to MultiSource.  Then add a NumberOfSource directive whose value is the number of source images you want to define.  Finally, add additional sections with names like [Source1], [Source2], and so on that contain the source directives for each of the individual source images.

 

Parameter
Description
Type = Multisource This directive simply informs the resample tool that this is a multi-source file.
NumberOfSources =n The number of [Source] sections in the file.

 

[Source] section

The parameters can be listed in any order in the section.

 

Parameter
Value(s)
Description
Default
Required
        
       
BMP/
TGA
GeoTiff/ Tiff
Raw
SDE
Vector GDB
General Parameters
               
Type

BMP

 

TGA

 

GeoTIFF

 

TIFF

 

 

Raw

 

 

SDE

 

 

VectorGDB

Windows bitmap

 

Targa image file

 

GeoTIFF file

 

For TIFF imagery that does not have GeoTIFF georeferencing tags

 

Raw BIP, BIL, or BSQ file

 

Remote SDE Geodatabase

 

Vector data in file or geodatabase

   required required required required required
Layer

Elevation

 

Imagery

 

LandClass

 

PopulationDensity

 

Region

 

Season

 

WaterClass

 

None

Elevation data

 

Aerial imagery

 

Land classification data

 

Population density

 

Cultural/environmental region data

 

Season data

 

Water classification data

 

Used only when the resampling is to provide a source for another source. See the notes for Channel_Red.

  required required required required required
                 
Source Location Parameters
                
Parameter
Value(s)
Description
Default
Required
        
       
BMP/
TGA
GeoTiff/ Tiff
Raw
SDE
Vector GDB
GDBDatabase text Geodatabase name         required required if GDBType = Remote
GDBFeatureClass text Vector feature class name           required
GDBInstance number Geodatabase instance (port number)         required required if GDBType = Remote
GDBPassword text Geodatabase user password         required required if GDBType = Remote
GDBRaster text Raster dataset name         required  
GDBServer text Geodatabase server name         required required if GDBType = Remote
GDBType File Local data file           required
  Local Local Access database            
  Remote Remote SDE database            
GDBUser text Geodatabase user name         required required if GDBType = Remote
SourceDir text Source file directory, in quotes.   required required required   required if GDBType = File or Local
SourceFile text Source file name, in quotes.   required required required   required if GDBType = File or Local
                 
Georeferencing Parameters
                
Parameter
Value(s)
Description
Default
Required
  
 
    
       
BMP/
TGA
GeoTiff/ Tiff
Raw
SDE
Vector GDB
GCS (geographic coordinate system)

WGS84

 

 

QMIDn

 

QMC

 

QMIC

 

World Geodetic System of 1984

 

Flight Simulator quad mesh identifier level 0-30.See QMID and LOD Values.

 

Flight Simulator quad mesh coordinate system

 

Flight Simulator quad mesh integer coordinate system

 WGS84 optional   optional    
nCols integer Number of columns       required   required
nRows integer Number of rows       required   required
PixelIsPoint

0 or 1

0: (ulxMap,ulyMap) at corner of pixel area


1: (ulxMap,ulyMap) at center of pixel area

 1 optional   optional   optional
ulxMap number Longitude of upper left pixel.   required required for TIFF required   required
ulyMap number Latitude of upper left pixel.   required required for TIFF required   required
xDim number

Size of each pixel in the X direction (Longitude) in degrees. For example:

9e-6 is 9 x 10 to the power of minus 6 degrees. See the table in QMID and LOD Values for some comparisons of meters and degrees per pixel.

In order for a texture to be reliably rendered in the near distance, this value should not exceed 4.27484E-05 (4.75meters per pixel).

  required required for TIFF required   required
yDim number Size of each pixel in the Y direction (Latitude) in degrees.   required required for TIFF required   required
                 
Sampling Parameters
                
Parameter
Value(s)
Description
Default
Required
  
 
    
       
BMP/
TGA
GeoTiff/ Tiff
Raw
SDE
Vector GDB
Bias number,... Bias added to sample values of each channel after scaling. For imagery sources use a comma-separated list: red,green,blue,[,land/water[,blend]]. For all other sources use a single value. 0.0 for all channels optional optional optional optional optional
Channel_Red integer.integer

One based source number and zero based band number used for the red color channel. If no source number is specified, the current source is used.

 

The tool can read color, land/water mask, or blend mask channel from any band of any image. By default, red, green, and blue are read from bands 0, 1, and 2 respectively. The land/water mask is read from band 3 and the blend mask from band 4. To override the defaults, use the Channel_ parameters.

 

To use a data source only to provide one or more channels for another source and to avoid sampling it directly, use Layer=None.

 0 optional optional optional optional optional
Channel_Green integer.integer Source number and band number used for the green color channel. 1 optional optional optional optional optional
Channel_Blue integer.integer Source number and band number used for the blue color channel. 2 optional optional optional optional optional
Channel_LandWaterMask integer.integer Source number and band number used for the land/water mask channel (waves, specular, reflections). 3 optional optional optional optional optional
Channel_BlendMask integer.integer

Source number and band number used for the blend channel.

 

This 8-bit blend mask channel for aerial imagery controls the transparency of the image when pasted onto the terrain. As an example this is used around the edges of the St. Maarten island image to blend gradually between the aerial photo water and the generic water. The blending channel is read from the 4th (zero-based) band of TIFF or GeoTIFF images, unless this parameter is used to change it.

 

See Example 4: Custom Terrain Texture with Water and Blend Channels for an example of the use of water and blend channels.

4 optional optional optional optional optional
Channel_Value integer.integer One-based Source number and zero-based band number used for monochrome values. If no source number is specified, the current source is used. 0 optional optional optional optional optional
DefaultValue number, … Values for each channel used if there is no data in the current pixel. For imagery sources use a comma-separated list: red,green,blue,[,land/water[,blend]]. For all other sources use a single value.   optional optional optional optional optional

FractionBits

 

BaseValue

integer, ...

 

integer

Scale multiplied by samples of each channel before biasing. Expressed as a number of fractional bits where scale = 1 / (1 << FractionBits). For imagery sources use a comma-separated list: red,green,blue,[,land/water[,blend]]. For all other sources use a single value.

 

See the section Using Scaled Elevation Values below.

0 for all channels optional optional optional optional optional
MajorityMode

Simple

 

 

 

 

Weighted

Simple majority of input samples determines the output value. Input samples are not weighted unless any sample weights are provided manually via SampleWeight parameter.

 

Automatically weight input sample values to preserve the statistical distribution of sample values from the input to the output. Automatic weights are overridden by any weights specified manually via the SampleWeight parameter.

 Simple optional optional optional optional optional
MaxValidValue number, … Maximum value for each channel that will be considered to be valid. Any value greater than this will be considered as missing data. For imagery sources use a comma-separated list: red,green,blue,[,water[,blend]]. For all other sources use a single value.   optional optional optional optional optional
MinValidValue number, … Minimum value for each channel that will be considered to be valid. Any value less than this will be considered as missing data. For imagery sources use a comma-separated list: red,green,blue,[,water[,blend]]. For all other sources use a single value.   optional optional optional optional optional
NullValue number, …

Sample value for each channel indicating that there is no data in the current pixel. For imagery sources use a comma-separated list: red,green,blue,[,land/water[,blend]]. For all other sources use a single value.

 

Typically NullValue might be set to 255,255,255, as white indicating no data.

  optional optional optional optional optional
SampleWeight.n value,weight For majority sampling, apply a manual weight to specific sample values, where n = 1 … NumberOfWeights   optional optional optional optional optional
SamplingMethod

Point

 

Majority

 

 

Dither

 

 

Bilinear

 

Gaussian

Simple point sample

 

Majority value within sample window prevails

 

Dither between nearest neighbors when oversampling. Fallback to point sampling when downsampling.

 

Bilinear interpolation

 

Gaussian interpolation

 Majority for classification data; Gaussian for continuous data optional optional optional optional optional
Scale number, ... Scale multiplied by each channel before biasing. For imagery sources use a comma-separated list: red,green,blue,[,land/water[,blend]]. For all other sources use a single value. 1.0 optional optional optional optional optional
                 
Raw Data Source Parameters
                
Parameter
Value(s)
Description
Default
Required
  
 
    
       
BMP/
TGA
GeoTiff/ Tiff
Raw
SDE
Vector GDB
BandGapBytes integer Number of bytes between bands (BSQ - Band Sequential layouts only). 0     optional    
BandLayout

BIL

 

BIP

 

BSQ

Band interleaved by line

 

Band interleaved by pixel

Band sequential (separate bands)

       required    
BandRowBytes integer Number of bytes per band per row nCols * sizeof( SampleType)     optional    
ByteOrder

Intel

 

Motorola

Least significant byte first

 

Most significant byte first

       required    
nBands integer Number of bands       required    
SampleType

UINT8

SINT8

UINT16

SINT16

UINT32

SINT32

UINT64

SINT64

FLOAT32

 

FLOAT64

8 bit unsigned integer

8 bit signed integer

16 bit unsigned integer

16 bit signed integer

32 bit unsigned integer

32 bit signed integer

64 bit unsigned integer

64 bit signed integer

32 bit IEEE floating point

64 bit IEEE floating point

       required   required
SkipBytes integer Number of bytes to skip at start of file 0     optional    
TotalRowBytes integer Total number of bytes per row

BIL: nBands * BandRowBytes

 

BIP: nCols * nBands * sizeof( SampleType)

 

BSQ: BandRowBytes

     optional    
                 
Season Data Source Parameters
                
Parameter
Value(s)
Description
Default
Required
  
 
    
       
BMP/
TGA
GeoTiff/ Tiff
Raw
SDE
Vector GDB
Month integer Month of the year (1-12) associated with Season data sources.   optional optional optional optional optional
                 
Imagery Data Source Parameters
                
Parameter
Value(s)
Description
Default
Required
  
 
    
       
BMP/
TGA
GeoTiff/ Tiff
Raw
SDE
Vector GDB
Variation

January

February

March

April

May

June

July

August

September

October

November

December

Day (all months)

LightMap or Night

All (day and night)

 Temporal variation (month or time of day) associated with Imagery data sources. LightMap images are used at night during all months. To associate a single image with more than one temporal variation, use multiple values separated by commas. For example, to use a single image in both January and February, type "Variation = January,February"   optional optional optional optional optional
                 
Vector Data Source Parameters
                
Parameter
Value(s)
Description
Default
Required
  
 
    
       
BMP/
TGA
GeoTiff/ Tiff
Raw
SDE
Vector GDB
VectorAttributeValue.n

whereClause, number

 

whereClause, fieldName

 Used by VectorGDB data sources to assign a value to polygons when rasterizing them. The whereClause is a SQL "where clause" that selects the relevant polygon features. To select all features, use an asterisk (*) for the whereClause. The number is the sample value to use when rasterizing the selected polygons. Alternately, a fieldName may be specified that determines the sample value to be assigned to the selected polygons. The first VectorAttributeValue must have a ".1" suffix and additional ones count up from there. For example VectorAttributeValue.1, VectorAttributeValue.2, etc.           required

 

 

Destination Parameters

 

The destination parameters are all held in a single [Destination] section, and the parameters can be listed in any order.

 

[Destination] section

 

Parameter
Value(s)
Description
Default
Required
DestFileType

BGL

 

BIP

Flight Simulator data file

 

Raw BIP file

 BGL optional
         
Destination Location Parameters
        
Parameter
Value(s)
Description
Default
Required
DestDir text Destination file directory, in quotes. If the directory does not exist, the tool will create it.   required
DestBaseFileName text Destination file name without an extension, in quotes. If the file already exists, it will be overwritten.   required
SplitDirLOD number Segment the resampled data into multiple destination subdirectories based upon the bounds of cells with the given LOD..   optional
SplitFileLOD number Segment the resampled data into multiple destination files based upon the bounds of cells with the given LOD. Must be greater than or equal to DestDirLOD (if used)..   optional
         
Georeferencing Parameters
        
Parameter
Value(s)
Description
Default
Required
GCS (geographic coordinate system, for BIP files only)

WGS84

 

 

QMC

 

 

QMIC

 

 

 

QMIDn

World Geodetic System of 1984

 

FS quad mesh coordinate system

 

FS quad mesh integer coordinate system

 

FS quad mesh identifier level 0-30

 WGS84 optional
NorthLat number North limit of sampling region in degrees. 90 optional
SouthLat number South limit of sampling region in degrees. -90 optional
EastLon number East limit of sampling region in degrees. 180 optional
WestLon number West limit of sampling region in degrees. -180 optional
BoundingCell level,u,v

QMID of single cell to bound the sampling region, and horizontal and vertical co-ordinates.

See QMID and LOD Values.

  optional
MinBoundingCell level,u,v QMID of cell forming the northwest bound of the sampling region, and horizontal and vertical co-ordidinates. Must be used with MaxBoundingCell.   optional
MaxBoundingCell level,u,v QMID of cell forming the southeast bound of the sampling region, and horizontal and vertical co-ordinates. Must be used with MinBoundingCell.   optional
UseSourceDimensions 0 or 1 If set to 1, match the sampling region to the bounds of the data sources.When UseSourceDimensions is enabled with multi-source files, Resample computes the union of the dimensions of all source the files. 0 optional
        
Sampling Parameters
       
Parameter
Value(s)
Description
Default
Required
CompressionQuality integer Quality of compression. A value of 100 indicates lossless compression and best quality. Smaller values indicate higher compression and lower quality. 100 optional
LOD [min,]max

Level of detail of each block of samples where LOD + 2 = QMID level. If this parameter is set as LOD=Auto, an appropriate level of detail is chosen to match the resolution of the source data.

See QMID and LOD Values.

7 for classification data and imagery. optional
MaxAutoLOD integer The maximum allowable LOD that can be selected if LOD=Auto.   optional
TextureWidth integer Texture width in pixels. One texture per block. 256 optional

 

Notes on .inf Files

 

The Geotiff File Format

Most of the data used by Flight Simulator can be modified using files in the Geotiff file format. In general this is the recommended method for making changes to the default data, because much of the complexity of the parameters for the data is held within the file, which makes resampling using this format quite easy. Another advantage is clearly that the data is viewable with a simple bitmap viewer, such as Microsoft Paint. For full details of this file format, refer to the following document:

Data that can be updated using Geotiff files includes: elevation, land class, water class, and population density. Data that cannot be updated using this format includes region and season data, this information is specific to Flight Simulator, and will need special treatment.

 

Using Scaled Elevation Values
Flight Simulator supports scaled elevation values. The elevation resampler provides a capability whereby very precise elevation values can be specified at the expense of the range of these values. By default, the resampler expects elevation values to be in increments of one meter. However, with the BaseValue and FractionBits directive, you can specify different scalings for source and/or destination data.

For example, say you had source data with elevation measurements precise within 1/128 of meter. Since elevation values are represented as a signed 16-bit integer, the range of values a given integer can express is -32768 to 32767. As stated above, the resampler's default behavior is to assume the given elevation values to be in meters, which means the default range of values is -32768 meters to 32767 meters.

If you set the FractionBits directive to 1 in the [Source] section of the .inf file, the resampler knows that the source data is in the form of "15.1" numbers. This means that each number has 15 bits reserved for the whole number part and 1 bit reserved for the fractional part.

With a single bit used for fractions, a number can be precise to within one-half (since the first place-value after the decimal point in a binary number represents one-half). From this, it is evident that a 15.1 number is more precise than a 16-bit integer; however, its range is half of a 16-bit integer. The range of a 15.1 number is -16384 to 16383.5. Each increment to the number represents an increment by 1/2. So, a 1 means 1/2 meter, a 2 means 1 meter, a 3 means 1.5 meters, and so on.

If we have source data precise to 1/128 meter. This means that a 1 equals 1/128 meter, a 2 equals 2/128 meter, and so on. To represent the example data properly, we need to specify 9 bits for the whole number part and 7 bits for the fraction part, or a 9.7 number. We do this with the following directive:

FractionBits = 7

Since 9 bits are reserved for the whole number part, the range is -512 to 511.984375. This is a fairly narrow range. Unless the area on the earth represented by this data is below 512 meters (and above -512 meters), there would be a problem representing the magnitude of the elevations. An elevation of 1000 meters, for example, cannot be expressed with a "9.7" scaled number. It is outside of the range. To solve this problem, the directive BaseValue can be used to define a "zero point" for the elevation values. For example, if the following is specified:

FractionBits = 7
BaseValue = 1000

A value of zero in the source data means 1000 meters. A value of 1 means 1000 + 1/128 meter (or 1000.78125).

You can use the FractionBits and BaseValue directives in either the [Source] or [Destination] sections, or in both sections. In the case where these directives specify different scalings in the [Source] and [Destination] sections, the resampler will attempt to form the source scale to the destination scale. If a loss of precision occurs, the resampler will print an error message.
 
QMID and LOD Values

 

QMID (Quad Mesh Identifier) values are an internal system used by Flight Simulator to optimize the textures required to represent the Earth, depending on the altitude the aircraft is flying at. Levels 0 and 1 are not used. At level 2 the Earth is divided into six quadrants, three for each hemisphere. Level 3 divides each of the quadrants in the higher level into four, and so on down to level 17 which gives a ratio of one pixel to 1.19 meters. Unfortunately the QMID levels do not match the LOD (Level of detail) levels exactly, there is an offset of 2 between these two indexing systems.

 

QMID level
LOD
Block size (degrees)
One Pixel (degrees)
Meters/pixel
2 0 90 0.350194553 38913.62
3 1 45 0.175097276 19456.81
4 2 22.5 0.087548638 9728.40
5 3 11.25 0.043774319 4864.20
6 4 5.625 0.02188716 2432.10
7 5 2.8125 0.01094358 1216.05
8 6 1.40625 0.00547179 608.03
9 7 0.703125 0.002735895 304.01
10 8 0.3515625 0.001367947 152.01
11 9 0.17578125 0.000683974 76.00
12 10 0.087890625 0.000341987 38.00
13 11 0.043945313 0.000170993 19.00
14 12 0.021972656 8.54967E-05 9.50
15 13 0.010986328 4.27484E-05 4.75
16 14 0.005493164 2.13742E-05 2.38
17 15 0.002746582 1.06871E-05 1.19
18 16 0.001373291 5.34354E-06 0.59
19 17 0.000686646 2.67177E-06 0.30
20 18 0.000343323 1.33589E-06 0.15
21 19 0.000171661 6.67943E-07 0.07
22 20 8.58307E-05 3.33972E-07 0.04
23 21 4.29153E-05 1.66986E-07 0.02
24 22 2.14577E-05 8.34929E-08 0.01
25 23 1.07288E-05 4.17464E-08 0.00
26 24 5.36442E-06 2.08732E-08 0.00
27 25 2.68221E-06 1.04366E-08 0.00
28 26 1.3411E-06 5.21831E-09 0.00
29 27 6.70552E-07 2.60915E-09 0.00

 

The QMID and LOD grids can be viewed using the TmfViewer tool, for example:

 

The following image shows the globe at with the QMID level 3 grid. The highlighted area is the base area around Hawaii, which is the dem data that was loaded into the tool. This file is dem0003.bgl in the scenery\0003 folder.
The following image shows Hawaii and the QMID level 11 grid. Note the latitude and longitude co-ordiantes of the pointer, which is in the grid square marked by the white circle, in the bar bottom right. The QMID level, u and v co-ordinates are in the bar, bottom left:
The following image shows Hawaii and the QMID level 12 grid (note the grid squares are one quarter the area of QMID level 11):

Resample Examples

All example .inf files are in the Terrain SDK/Resample Examples folder. The output from running the examples will be placed in the Terrain SDK/Resample Examples/Output folder. The input is in the Terrain SDK/Resample Examples/SourceData folder, and can be examined just by double clicking on the files to open them up in an image viewer.

Example 1. Replacing Elevation Data

 

To run this example, drag the DeathValley_Elevations.inf file onto the Resample tool icon.

Textures for all appropriate levels of detail are created by the Resample tool, and stored in the BGL files. For the Death Valley example, the tool creates and stores textures only in LODs 2-10. You can confirm this by opening DeathValley_Elevations.bgl in TmfViewer by expanding the "Level of Detail" item on the View menu. When you do this you will notice that only levels 2-10 are enabled in the menu.  All the other levels are grayed out because they do not exist in the bgl file. The images below show Death Valley elevation data from QMID level 2 to level 10.

Death Valley at QMID level 2
Death Valley at QMID level 4
Death Valley at QMID level 6
Death Valley at QMID level 8
Death Valley at QMID level 10

 

Notes on Acquiring Raw Digital Elevation Data

A DEM provides a digital representation of a portion of the earth's elevation points over a two-dimensional surface. A DEM is generated by sampling an array of elevation values derived from topographic maps, aerial photographs, or satellite images.
There are a number of places to get digital elevation data. Most terrain data available for free over the Internet is typically stored in formats such as the USGS DEM (Digital Elevation Model) ASCII, USGS TAR, or USGS Spatial Data Transfer Standard (SDTS) formats. All source data is expected to use WGS84 projection.

For example, this is a link to the USGS 100 meter DEM for the entire United States of America. Just click on the area of DEM you want:
http://edcwww.cr.usgs.gov/glis/hyper/guide/1_dgr_demfig/index1m.html

The raw data used when creating terrain for Flight Simulator must be in a binary file format, with each elevation point (measured in meters above mean sea level) being assigned a 16-bit integer. The resampler supports both LSB (least significant byte first) and MSB (most significant byte first) 16-bit integers.

The USGS DEM and SDTS formats are not compatible with the terrain tools included with this SDK, but there are converters available (free of charge) on websites that convert the data to a compatible binary form. For example, see the read_dem.exe tool that’s available for download at http://dbwww.essc.psu.edu/notes/utilities.html. After using this tool, you should be able to run the output DEM data through the Resample tool.

 

You may find that the source files you acquire come with a header file. This header file provides the information needed for some sections of the .inf file such as the bounding area.

Example 2: Creating new Land Classifications

 

To run these examples, drag the LandClass_AutoWeightedMajority, LandClass_Dither, LandClass_ManualWeightedMajority, LandClass_PointSample and LandClass_SimpleMajority .inf files onto the Resample tool icon. The output can be viewed in TmfViewer, and should look like the images shown below. If an image is not showing in TmfViewer after loading, check the Level of Detail menu, to be sure that one of the appropriate levels of detail has been selected.

 

LandClass Auto Weighted example LandClass Dither example
LandClass Manual Weighted example LandClass Point example
LandClass Simple Majority example  
 

 

 

Example 3: Creating Custom Terrain Textures

 

To run these examples, drag the MillenniumImage and DayNight_Variations .inf files over the Resample tool icon.

 

The Millennium example illustrates a couple of concepts, the use of a GeoTIFF image with Resample, using a source image with transparent "NullValue" pixels, setting the lossy compression quality to 75%, and using an automatic selection for the LOD levels. The Resample tool outputs a range of LODs appropriate for the source image. After the Resample tool finishes, open the resulting .BGL file in TmfViewer to view the imagery. You can also drop the .BGL file in Microsoft Flight Simulator X/Addon Scenery\scenery to view it in the game. The imagery will appear near N47.68, W122.1.

 

The DayNight_Variations example shows how two different textures apply during different daylight hours. It also shows the use of mutliple source files, and the providing of co-ordiantes within the .inf file, rather than the raw data. The resulting textures can be viewed in TmfViewer, or in the game if the bgl file is moved to Microsoft Flight Simulator X/Addon Scenery\scenery. In TmfViewer chose different Levels of Detail to view the image, and check on Night in the Seasons/Variations submenu to see the nighttime image. To view the imagery in the game, use the Map feature and enter 0 into the Latitude box. You will be flying around the open Pacific and the images will be rendered onto the sea (see the screen shots below).

 

These examples show how to add custom satellite or aerial imagery to the terrain in Flight Simulator X. These are simply the textures used to render onto the terrain, to add buildings and trees to custom textures, follow the directions in the Autogen annotation document.. Areas in Flight Simulator like New York City, Chicago, and Las Vegas were created using the methods discussed here, and in the Autogen document..

 

Millennium Buildings: note the white space around the edges is removed by setting the NullValue parameter to 255,255,255.

 

Day
Night
Dawn
Dusk: note the merging of both the Day and Night variations

 

Notes on Acquiring Raw Terrain Imagery

 

More than likely, the image you want to use will be an aerial or satellite photo. The raw image must be either a 24-bit per pixel Windows .bmp file or a 32-bit per pixel Targa .tga file.  For some file formats, you can use Imagetool to convert the image into the desired format. It is assumed that the image has been projected to the WGS84 Latitude/Longitude datum. The latitude and longitude of the northwest corner of the image must be known as well as the spacing (in decimal degrees) between the image pixels.


To add reflective water effects to an image, you must use the 32-bit per pixel Targa .tga format.  The resampler tool uses the 8-bit alpha channel of the image to determine the location of water and land in the image.  The alpha value of water and land pixels must be 0 and 255 respectively.

The north/south extent of each terrain texture pixel is about 1.19 meters in Flight Simulator X (it was 4.75m in Flight Simulator 2004). The resampling process will filter the raw image to the right size.
•    If the raw image is more than 1.19 meters per pixel (low resolution), the final result may appear blurry.
•    If the raw image is less than 1.19 meters per pixel (high resolution), some fine details might be lost.

Example 4: Custom Terrain Texture with Water and Blend Channels

 

To run this example drag the MilleniumImage_water_blend.inf file over the Resample tool icon.

 

The example shows the use of the water and blend channels, and can be compared with the Millennium Buildings in Example 3.

 

The following image shows the source: Millennium_water_blend.tif
The following image shows the Millennium_water_blend.bgl file, loaded into TMFViewer, with the Level of Detail set to 17.
The following image shows the Millennium_water_blend.bgl file, loaded into TMFViewer, with the missing data and water mask menu items selected.

 

Example 5: Multiple Source and Blend Channels

 

To run this example drag the Multichannel_Multisource.inf file over the Resample tool icon.

 

The example shows how to read the land/water mask and/or blend mask from separate files from the main color channels. Note that white (RGB: 255,255,255) is land and black (RGB: 0,0,0) is water. If you want the default water color to show through, you must paint entirely black pixels into the source image containing the color channels. Anything other than black will be used as is but with reflective water effects. The location of the new terrain is at Latitude 0, Longitude -122.308. Examine the Blend Mask and LandWater Mask files and the following screen shot taken from within Flight Simulator.

 

 

 

Place the new Files in Flight Simulator

The easiest way to add a new .bgl file to Flight Simulator is to copy it into the Addon Scenery\Scenery directory. Files in this directory are treated as higher priority than those in other directories, so new terrain data here will be rendered in preference to lower priority data elsewhere. However, for complex new additional scenery, it is probably more useful to create a folder for the custom scenery area. This will enable a user to select and deselect the scenery using the Scenery Library dialog.


To create the appropriate directories:

  1. Create a new scenery area folder, with an appropriate name. Within each scenery area, create two subdirectories: Scenery and Texture.
  2. Place any .bgl files into the Scenery directory.
  3. Place any necessary .bmp files into the Texture directory.
  4. Run Flight Simulator and choose Scenery Library under the Settings tab.
  5. Click the Add Area button and fill in the blanks.The new scenery area will not be visble in Flight Simulator until you restart the program.

The final step is to view the new data within Flight Simulator, and go back and repeat the resampling steps if it is not quite right (possibly resampling to a higher or lower resolution).

Appendix I: Comparison of Flight Simulator 2004 and X Regions

The following diagram shows the regions in Flight Simulator X compared with those in FS 2004. No additions have been made to the water class system.

Appendix II: The World Coordinate System

One of the most powerful features of BGL is that everything is based on a world coordinate system that is spherical and very much like latitude/longitude.

In Flight Simulator, the earth is defined as an “oblate spheroid,” an ellipse rotated about its minor axis. In terms of shape, it's much like a sphere that is a little bit fat around the equator. In Flight Simulator, the earth has the following dimensions:
•    Equatorial diameter=12756.27 km
•    Equatorial circumference=40075.0 km
•    Polar diameter=12734.62 km
•    Polar circumference=40007.0 km

Unlike other 3-D graphics systems (rectilinear systems that overlay a square grid over a map that is really a portion of a sphere), the position of scenery in BGL is specified in world coordinates. The following table includes the elements of the world coordinate system used by BGL and Flight Simulator to specify position in the world.

Dimension
Representation
Longitude 0 at 0° longitude. East is positive; west is negative with overflow wrap at 180°.
Altitude 0 at sea level. Positive is up; negative is down.
Latitude 0 at equator. Positive is north; negative is south.

Although the position of objects on the earth is specified in the world coordinate system, actual design work is done in smaller rectilinear coordinate systems placed with their centers at a given world coordinate.

The Object Coordinate System

The object coordinate system is used to design scenery. The object coordinate system is based on the X, Y, Z concept of design space. The rectilinear, 3-D X, Y, Z coordinate system is set up with its center, X=Y=Z=0, at the specified latitude, longitude, and altitude. The Z-axis aligns with true north (parallel to lines of longitude), the X-axis aligns with east (parallel to lines of latitude), and the Y-axis aligns with altitude. You can define points, lines, and polygons within the X, Y, Z design space.
The X, Y, and Z-axes each have a range of +/-32767 (16-bit linear design space). The size that each unit along the axes represents depends on the scale factor. The scale factor can range from less than 1 millimeter per unit to 32768 meters per unit.
The object design system creates some interesting design problems not unlike those in the real world. For example, a 1 mile square section of land in the northern hemisphere encompasses more longitude at its northern edge because this edge is further north on the sphere. Conversely, a "square" piece of land that has its east and west borders precisely aligned with lines of longitude and its north and south borders aligned with lines of latitude isn’t really square because its north edge is shorter than its south edge. When aligning many square pieces on the earth’s surface, the result is either some pieces that aren’t square or small gaps between some pieces.

The Coordinate System, Basic Principles

The coordinate systems used in Flight Simulator are left-hand, 3-D, and rectilinear. Objects are located in X,Y,Z 3-D space and are moved in the X,Y, and Z directions using translation. The following table describes how this directional translation of an object occurs in the world as well as on the screen.

Dimension
World movement
Screen movement
+X West to east  Left to right
+Y Increasing altitude  Bottom to top
+Z South to north  Into the screen

Flight Simulator directional conventions include the following:
•    The surface of the earth is laid out on the X-Z plane.
•    Northerly movement is in the positive Z direction.
•    Easterly movement is in the positive X direction.
•    Increasing altitude movement is in the positive Y direction.
•    World directional movement corresponds to display screen directional movement when the viewer is facing north. For example, an easternly moving object moves to the right across the screen when the viewer is facing north.

Flight Simulator uses Euler angles for rotations; first heading is applied, then pitch, and finally bank. The following table describes the rotational conventions.
Rotation
World rotation
Screen rotation
+Heading, rotate about the Y-axis Rotate to the right; 0° is north Object moves left as heading increases.
+Pitch, rotate about the heading-rotated X-axis Nose down Object moves upward (+Y) as pitch increases.
+Bank, rotate about the heading-rotated and pitched Z-axis  Rotate counter-clockwise   The object rotates clockwise as bank increases.


Directional translation and rotation are applied to objects before they are projected. The order in which directional translation and rotation are applied makes a difference because the rotations have the effect of "rotating" the coordinate system. Translation and rotation are performed in the following order:
1.    Translate X.
2.    Translate Y.
3.    Translate Z.
4.    Rotate heading (about the Y-axis).
5.    Rotate pitch (about the heading-rotated X-axis).
6.    Rotate bank (about the heading-rotated and pitched Z-axis).

Appendix III: The Naming Convention for Terrain Textures

This section describes the naming convention used by Flight Simulator for terrain (land based) textures. The textures are found in the Microsoft Flight Simulator X/scenery/World/texture folder. The naming convention follows the format:

 
000X2SU1

 

Name Element
Description
000 The texture number (000, 001, and so on).
X Region (A through X), see Regions.
2 Reserved, must always be 2.
SU Season, one of: spring (SP), summer (SU), fall (FA), winter (WI), hard winter (HW), night texture (LM), or Autogen annotation (AN). See Seasons.
1 Variation (1, 2, 3, and so on).

 


 

© 2006 Microsoft Corporation. All rights reserved.

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