View source for AGN (FSX)

{{Infobox-Applicable-FSVersion
| FSXI = false
| FSXA = true
| FSX = true
| FS2004 = false
| FS2002 = false
| FS2000 = unknown
| FS98 = unknown
}}

This document describes the FSX format for autogen (AGN) files.

== Sections ==

The AGN file uses the RIFF format (like MDL files), this means that the file consists of different sections. Each section starts with a four character label, followed by the length of the section in bytes (this length without the header itself).

The main RIFF section itself has one additional parameter, this is a four character string that indicates the type of RIFF AGN file. For an FSX AGN file the value should always be AGNX.

The following subsection show more details about the content of these different sections. 

=== VERS ===

Contains versions information about the AGN file.

  int32 version (normally 1091777331)

=== GBDD ===

Contains information about autogen generic buildings

  int32 percentage of 1 and 2 floor buildings (normally 10)
  int32 percentage of 3 to 5 floor buildings (normally 10)
  int32 percentage of 6 to 8 floor buildings (normally 10)
  int32 percentage of 9 to 12 floor buildings (normally 10)

Valid values for percentage are from 0x00 (0%) to 0x14 (100%).

=== GBTE ===

This section contains the name of the texture to use for the generic buidlings. The texture name is stored without extension and the length seems to be a multiple of 4.

=== RHTE ===

This section contains the name of the texture to use for the row houses. The texture name is stored without extension and the length seems to be a multiple of 4.

=== GBLD ===

Contains building information. This section contains one or more [[#GBLR|GBLR]] sections.

==== GBLR ====

Contains information about Generic Buildings.

  GUID roof type (will use default roofs, if 0)

For each Generic Building:

  float X position of first point 
  float Y position of first point
  float X direction to the second point
  float Y direction to the second point
  float X offset of third point
  float Y offset of third point 

The x and y coordinates are given as offset from the middle of the LOD13 square (range -0.5 till 0.5).

=== PREG ===

Contains vegatation information. This section contains one or more [[#PRDE|PRDE]] sections.

==== PRDE ====

For vegatation polygon. Contains:

  GUID vegatation type

For each polygon:

  int number of vertices

For each vertex:

  single x
  single y

The x and y coordinates are given as offset from the top left of the LOD13 square (range 0 till 1). The first and last vertex of the polygon have to be the same (so the polygon has to be closed).

=== VGRG ===

Contains information about FSX style rectangular vegetation regions. This section contains one or more [[#VGRE|VGRE]] sections. The type of vegetation is defined by a GUID.

==== VGRE ====

  GUID vegetation type

For each rectangle:

  float X position of first point
  float Y position of first point
  float X offset to second point
  float Y offset to second point 

The x and y coordinates are given as offset from the middle of the LOD13 square (range -0.5 till 0.5).

=== VGRD ===

Contains information about the FS2004 vegetation definition.

  int vegetation class 1
  int vegetation class 2
  int percentage vegetation class 1 (0-100)
  int maximum density
  float minimum height class 1
  float maximum height class 1
  float minimum height class 2
  float maximum height class 2

=== VGRO ===

Contains information about FS2004 style rectangular vegetation regions. The type of vegetation is defined in the [[#VGRD|VGRD]] section.

For each rectangle:

  float X position of first point
  float Y position of first point
  float X offset to second point
  float Y offset to second point 

The x and y coordinates are given as offset from the middle of the LOD13 square (range -0.5 till 0.5).

=== ROWH ===

Contains information about row houses. The amount of houses is the length of the section divided by 24.

For each row house:

  float X position of first point
  float Y position of first point
  float X direction to second point
  float Y direction to second point
  float X offset to third point
  float Y offset to third point 

The x and y coordinates are given as offset from the middle of the LOD13 square (range -0.5 till 0.5).

=== AGN2 ===

Contains information about library objects. Contains one or more [[#A2GE|A2GE]] sections.

==== A2GE ====

Contains information about library objects.

  GUID library object guid

For each library object:

  float X position of first point
  float Y position of first point
  float X direction to second point
  float Y direction to second point

Optional:

  float X offset to third point
  float Y offset to third point 

The x and y coordinates are given as offset from the middle of the LOD13 square (range -0.5 till 0.5). The coordinates describe the bounding box, the actual library object is placed in the center of it.

=== PBLD===

Contains information about polygon buildings. Contains one or more [[#PBDE|PBDE]] sections.

==== PBDE====

  GUID building type

For each building:

  int32 1 (seems always to be 1)
  float extrusion width
  int32 number of footprint vertices

For each vertex:

  single x
  single y

The x and y coordinates are given as offset from the top left of the LOD13 square (range 0 till 1).


== LOD 13 Geographical Location  ==

The geographical location of the LOD13 square associated with the AGN file is encoded in the file name.<br/>
The file name is in the format : xxxxxan.agn, where the xxxxx part, with a length of 15, is made of the following digits: 0,1,2 and 3

=== Encoding the LOD13 geographical location in the file name ===
Let's say that the upperleft position of the LOD13 square is:<br/>
Latitude: N45.51<br/>
Longitude: W73.38<br/>
<br/><br/>
This corresponds to the QMID square U=7278, V=4049, Level =15  (Remember that QMID Level = LOD Level + 2)<br/>
We then convert the U and V values in binary format:<br/>
<pre>
U = 7278 = 1110001101110
V = 4049 =  111111010001
</pre>
However, for the V value, we replace the '1' with '2'<br/>
<pre>
So V = 4049 = 222222020002
</pre>

Finally we add U + V with their respective binary format
<pre>
U: 1110001101110
+
V:  222222020002
=
   1332223121112
</pre>
If needed, we left-pad the result with zeroes to have a length of 15
<pre>
001332223121112
</pre>
So the resulting AGN file will be : 001332223121112an.agn.<br><br>
The reason the length is 15 is because the maximun U value for LOD13 is 24575 which has a binary value of 101111111111111  (15 characters)

=== Decoding the LOD13 geographical location from the file name ===
Let's say the file name is 001332223121112an.agn<br/>
We extract the numerical part to compute the U and V values (QMID Level is always 15)<br/>
To get the U value, we replace the '3' with '1' and '2' with '0'<br/>
To get the V value, we replace the '1' with '0' and the '3' and '2' with '1'<br/><br/>
<pre>
   001332223121112
U: 001110001101110b = 7278d
V: 000111111010001b = 4049d
</pre>
So the agn file corresponds to the QMID square (u=7278, v =4049, l=15)<br/>
Once we have the u and v values, the upperleft coordinates of the square are:<br/>
<pre>
LongitudeDeg = u * 0.0146484375 - 180
LatitudeDeg = 90 - v * 0.010986328125
</pre>
[[Category:Terrain Design]]
[[Category:File_Formats]]
[[Category:Autogen]]