Here is a description of what I got so far.
My aim is to apply high resolution pictures to the terrain. I want to try 1.2meter/pixel resolution (using 1024 x 1024 bitmaps) and 2.4meter/pixel resolution (using 512 x 512 bitmaps). I want to integrate this with the "normal" VTP photo scenery already implemented in SBuilder. The VTP photo scenery uses textures of 256 x 256 pixels corresponding to a resolution of 4,8 meter/pixel.
I used the Atlantic as test region. Note that I am using test data and no real data or pictures. I pick up the Cell at N40 W40 and I used a mesh map as depicted in the figure:
You note 6 photo tiles on the top on a plan region and 6 other photo tiles on the center on a mountain region. This mesh map is precisely a 257 x 257 bitmap which was converted from a 257 x 257 BSQ file of altitudes. The first thing that I would like to focus is that I altered the calibration of the map. The borders for the 298_142 Cell are:
North=40.078125
South=39.7265625
West=-40.3125
East=-39.84375
but I expanded by 1/2 of a pixel in each direction. With a pen and paper you can see that this expansion corresponds to the following values:
[GEOGRAPHIC]
North=40.07881165
South=39.72587585
West=-40.31341553
East=-39.84283447
and look to the NW corner of the display to see the 1/2 pixel display:
The reason for this is to make the FS sampling grid to be the center of the pixel. I add another parameter to the INI file called ExtMeshBitmap:
[Main]
ExtMeshBitmap=True
If I extend my mesh bitmap by 1/2 of pixel on the 4 directions I set ExtMeshBitmap=True in order to get the same final mesh BGL as if I had not done that. You can skip the following orange part which shows how I use the ExtMeshBitmap parameter in creating the INF file for mesh generation:
<font color="orange">
' create the INF
Open App.Path + "\tools\work\" + FileMeshName + ".INF" For Output As #3
Print #3, "[Source]"
Print #3, " Type = ElevS16LSB"
Print #3, " SourceDir = "; Chr(34); "."; ; Chr(34)
Print #3, " SourceFile = "; Chr(34); FileMapName; Chr(34)
NLAT = Maps(Map).NLAT2
SLAT = Maps(Map).SLAT2
WLON = Maps(Map).WLON2
ELON = Maps(Map).ELON2
ROWS = Maps(Map).Rows2
COLS = Maps(Map).Cols2
If ExtMeshBitmap Then
Delta = (NLAT - SLAT) / ROWS / 2
NLAT = NLAT - Delta
SLAT = SLAT + Delta
Delta = (ELON - WLON) / COLS / 2
WLON = WLON + Delta
ELON = ELON - Delta
End If
Print #3, " CellType = S16LSB"
Print #3, " NullCellValue = -32768"
Print #3, " Lat = "; CStr(NLAT)
Print #3, " Lon = "; CStr(WLON)
Print #3, " NumOfCellsPerLine = "; CStr(COLS)
Print #3, " NumOfLines = "; CStr(ROWS)
Print #3, " CellXdimensionDeg = "; CStr((ELON - WLON) / (COLS - 1))
Print #3, " CellYdimensionDeg = "; CStr((NLAT - SLAT) / (ROWS - 1))
Print #3, " ScaleinMeters = 1"
</font id="orange">
In the picture above the thick red line marks the LOD8 grid (the corner of a Cell), the thin red line marks the LOD13 grid (or Areas or photo tiles) and the red dot line marks the LOD16 grid. This LOD16 grid is the sampling grid for "LOD8" mesh scenery. In applying photo textures I force the terrain to be a LOD8 mesh. To achieve this I added a button to the Mesh Properties window:
The button is called "Make Flattens" and if I press it, SBuilder looks for photo-tiles (remember I had 6 + 6 = 12) that have a bitmap mesh underneath. For all the photo tiles that are "planted" on a mesh map, SBuilder reads the altitudes of the mesh map (that is why I extended the mesh maps 1/2 pixel) and creates 128 LWM flatten triangles (either LWM2 or LWM3). Here is the result:
If I zoom in we can see the triangles. You will see that the vertices do not coincide. This was the best I could do for the flatten (tilted) triangles to follow the mesh.
The idea was to force the mesh to be a set of triangles so that I could paint those triangles with the detailed textures. <b>I had limited success here!</b> Even reducing TERRAIN_MAX_VERTEX_LEVEL=18 (maximum mesh resolution = LOD8) I could not get the triangles to behave as I expected. I do not know if I keep this. May be I left it as it stands and I add some more parameters to the INI files such as:
AltitudeGap=
ZbiasValue=
For example I could set AltitudeGap=2 meters to force the textured triangles to be 2 meters higher than the mesh. But to understand the problem I need to refer to the photo triangles. I changed the compilation window regarding to photo scenery:
On the top left corner I have 2 more check boxes. The Make Bitmaps is not ready yet but it simple will generate 512 x 512 or 1024 x 1024 bitmaps. These bitmaps will be high resolution "replicas" of the normal 256 x 256 bitmaps used in VTP photos. This make life easier if the flattens, describe above, fail to force the mesh to be "LOD8 triangles". The other check box is Make BGLs. This will generate trianngles whose vertices coincide with the vertices of the flatten triangles. Here is the code (the texture list part is not yet finished - also seasons to be included!):
<font color="green">
Header( 1 41 39 -39 -41 )
LatRange( 39 41 )
; High Resolution Photo # 1
Area( B 40.05065918 -40.18798828 50 )
LayerCall( :lcall 4 )
Jump( : )
:lcall
RefPoint( 2 :return 1 40.05065918 -40.18798828 E= 0 v1= 20000 v2= 1200 )
BGLVersion( 0800 )
TextureList( 0 6 FF 255 255 255 0 50.000000 "green.bmp" )
MaterialList( 0 0.10 0.80 0.20 1.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 1.00 0.00 )
VertexList( 0
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156.0401 0419.050 152.8885 0.0 1.0 0.0 0.625 0.625 ; vertex #050
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624.1227 0374.050 611.5540 0.0 1.0 0.0 1.000 1.000 ; vertex #080
)
Zbias( 25 )
SetMaterial( 0 0 )
DrawTriList( 0
000 010 009 000 001 010 001 002 010 002 011 010 009 010 018 010 019 018 010 020 019 010 011 020
018 028 027 018 019 028 019 020 028 020 029 028 027 028 036 028 037 036 028 038 037 028 029 038
036 046 045 036 037 046 037 038 046 038 047 046 045 046 054 046 055 054 046 056 055 046 047 056
054 064 063 054 055 064 055 056 064 056 065 064 063 064 072 064 073 072 064 074 073 064 065 074
002 012 011 002 003 012 003 004 012 004 013 012 011 012 020 012 021 020 012 022 021 012 013 022
020 030 029 020 021 030 021 022 030 022 031 030 029 030 038 030 039 038 030 040 039 030 031 040
038 048 047 038 039 048 039 040 048 040 049 048 047 048 056 048 057 056 048 058 057 048 049 058
056 066 065 056 057 066 057 058 066 058 067 066 065 066 074 066 075 074 066 076 075 066 067 076
004 014 013 004 005 014 005 006 014 006 015 014 013 014 022 014 023 022 014 024 023 014 015 024
022 032 031 022 023 032 023 024 032 024 033 032 031 032 040 032 041 040 032 042 041 032 033 042
040 050 049 040 041 050 041 042 050 042 051 050 049 050 058 050 059 058 050 060 059 050 051 060
058 068 067 058 059 068 059 060 068 060 069 068 067 068 076 068 077 076 068 078 077 068 069 078
006 016 015 006 007 016 007 008 016 008 017 016 015 016 024 016 025 024 016 026 025 016 017 026
024 034 033 024 025 034 025 026 034 026 035 034 033 034 042 034 043 042 034 044 043 034 035 044
042 052 051 042 043 052 043 044 052 044 053 052 051 052 060 052 061 060 052 062 061 052 053 062
060 070 069 060 061 070 061 062 070 062 071 070 069 070 078 070 079 078 070 080 079 070 071 080
)
EndVersion
:return
Return
EndA
; High Resolution Photo # 2
</font id="green">
Now it is time for real world pictures with a GREEN TESTING TEXTURE! As I described I could not match the textured triangles with the "triangular mesh". Therefore the mesh (256 x 256 bitmaps) will protude, on same places, the green texture specially when I am very closed. The problem is severe on mountains regions. Using ZBias() can aleviate the effect. I have more tests to run.
This is the mountain part (6 photos all green)
and this is the flatten area:
Regards, Luis