FSX FSX AGN format

[GHD]

Has anyone decoded the VGRD record in an FSX format agn file?

It contains 32 bytes and seems to be two GUIDs, but what do they mean?

 

[GHD]

They are not GUIDs, the first four words are integers representing:

Vegetation type 1
Vegetation type 2
Relative density of type 1
Relatibe density of type 2

I would have expected the next four words to be floats:

Minimum height for type 1
Maximum height for type 1
Minimum height for type 2
Maximum height for type 2

But this doesn't seem true, they contain hex values:

#00004041
#0000c041
#00004041
#0000c041

The equivalent FS9 format fields are integers

12
24
12
24

So it seems that #00004041 is 12 and #0000c041 is 24

 

[arno]

Hi George,

Yes, 00004041 is the hex representation of 12.0 and 0000c041 is 24.0 as a float. So that is right.

Once you have figured it out, will you update the information in the Wiki about the AGN format?

 

[GHD]

Hi Arno,

Thanks for your input. I must have a problem in my C++ code. This is what I use to print four bytes in hex, integer and float format:

void GenPrint(int v)
{
  unsigned char c1;
  unsigned char c2;
  unsigned char c3;
  unsigned char c4;
  typedef union
  {
    int i;
    float f;
    unsigned char c[4];
  } ALL;

  ALL w;

  w.i = v;
  c1 = w.c[0];
  c2 = w.c[1];
  c3 = w.c[2];
  c4 = w.c[3];

  TRACE("#%02x%02x%02x%02x    %d    %f\n", c1, c2, c3, c4, w.i, w.i, w.f);

}

The hex and integer output is correct. but the output of all floats is 0.0:

#01000000    1    0.000000
#02000000    2    0.000000
#58000000    88    0.000000
#64000000    100    0.000000
#00004041    1094713344    0.000000
#0000c041    1103101952    0.000000
#00004041    1094713344    0.000000
#0000c041    1103101952    0.000000

I would be grateful if you could tell me where am I going wrong.

 

[arno]

Hi,

Could it be that you have w.i twice in the TRACE command? So I think your float is never printed to text.

 

[GHD]

Hi,

Could it be that you have w.i twice in the TRACE command? So I think your float is never printed to text.

I just realised

I have now decoded FSX format files containing vegetation rectagles. What is interesting is that there is no definition of the vegetation type other than the integers 1 and 2 indicating deciduous and coniferous.

The next and more difficult phase is to decode polygon areas, buildings and library objects. Still continuing the investigation.

 

[arno]

I assume you saw this article already, which has part the vegetation polygons explained already.

 

[GHD]

I assume you saw this article already, which has part the vegetation polygons explained already.

No, I hadn't seen that article. The section VGRG may contain information on pre-FSX style rectangulat vegetation regions, but all of the files I have examined have VGRD and VGRO section containing this information: