So, at the moment, I have GeoTIFF files and I'm using TGLHeightField to display the grid and create a DEM. The GeoTIFF files are huge and the performance of TGLHeightfield has fallen offa cliff, so I'm looking at TGLTerrainRenderer instead. TGLHeightTileFileHDS seems to be perfect for what I need to do, so I'm trying to create the HTF file from the TIFF using TGLHeightTileFile.
When trying to add the height value, my data consists of Single values, but TGLHeightTileFile.CompressTile(x, y, ts, ts, @buf[0]) is a SmallInt array? That's nowhere near the precision or range I need. Am I missing something, or going about this the wrong way?
Cheers
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I struggled with this as well when I first implemented the TGLTerrainRenderer many years ago. It is not logic at all, but you need to normalize the vertical scale of TGLTerrainRenderer with the actual range of your data.
The procedure below is taken out of context, but I think you can see what it is doing.
procedure TGridTerrain.UpdateHDSScale;
var
HDSMaxAbsValue : Double;
begin
inherited;
HDSMaxAbsValue := 32767;
if (Grid.MaxValue - Grid.MinValue) <> 0 then begin
if Abs(Grid.MaxValue) > Abs(Grid.MinValue) then begin
HDSMaxAbsValue := Abs(Grid.MaxValue);
end else
if Abs(Grid.MaxValue) < Abs(Grid.MinValue) then begin
HDSMaxAbsValue := Abs(Grid.MinValue);
end;
end;
FHDSScale := 32767 / HDSMaxAbsValue;
end;
The procedure updates the scaling factor FHDSScale which is applied elsewhere in the code:
FGLTerrainrenderer.Scale.Z := FHDSScale;
When you add your elevation values:
RasterLine[X - HeightData.XLeft] := Elevation * FHDSScale;
Materials need to be scaled as well
The TGLTerrainRenderer and related components are made for large terrains but because they so hard to use, undocumented, and also plagued with bugs I have moved away from them. I use only small terrains so for me a TGLFreeform does the job and is much simpler to implement.
Lars
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Thanks for that - it's saved me days of effort. I got wrapped up in another issue that's needing sorted first. I was struggling to get sensible data from some TIFFs, but I think it's because they're way over the 4Gb limit and have been saved as BigTIFFs, so I need a Delphi unit/library that handles BigTIFF.
Some months are just like the labours of Sisyphus ....
Eric
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Hi,
So, at the moment, I have GeoTIFF files and I'm using TGLHeightField to display the grid and create a DEM. The GeoTIFF files are huge and the performance of TGLHeightfield has fallen offa cliff, so I'm looking at TGLTerrainRenderer instead. TGLHeightTileFileHDS seems to be perfect for what I need to do, so I'm trying to create the HTF file from the TIFF using TGLHeightTileFile.
When trying to add the height value, my data consists of Single values, but TGLHeightTileFile.CompressTile(x, y, ts, ts, @buf[0]) is a SmallInt array? That's nowhere near the precision or range I need. Am I missing something, or going about this the wrong way?
Cheers
Hi Eric,
I struggled with this as well when I first implemented the TGLTerrainRenderer many years ago. It is not logic at all, but you need to normalize the vertical scale of TGLTerrainRenderer with the actual range of your data.
The procedure below is taken out of context, but I think you can see what it is doing.
procedure TGridTerrain.UpdateHDSScale;
var
HDSMaxAbsValue : Double;
begin
inherited;
HDSMaxAbsValue := 32767;
if (Grid.MaxValue - Grid.MinValue) <> 0 then begin
if Abs(Grid.MaxValue) > Abs(Grid.MinValue) then begin
HDSMaxAbsValue := Abs(Grid.MaxValue);
end else
if Abs(Grid.MaxValue) < Abs(Grid.MinValue) then begin
HDSMaxAbsValue := Abs(Grid.MinValue);
end;
end;
FHDSScale := 32767 / HDSMaxAbsValue;
end;
The procedure updates the scaling factor FHDSScale which is applied elsewhere in the code:
FGLTerrainrenderer.Scale.Z := FHDSScale;
When you add your elevation values:
RasterLine[X - HeightData.XLeft] := Elevation * FHDSScale;
Materials need to be scaled as well
The TGLTerrainRenderer and related components are made for large terrains but because they so hard to use, undocumented, and also plagued with bugs I have moved away from them. I use only small terrains so for me a TGLFreeform does the job and is much simpler to implement.
Lars
Hey Lars,
Thanks for that - it's saved me days of effort. I got wrapped up in another issue that's needing sorted first. I was struggling to get sensible data from some TIFFs, but I think it's because they're way over the 4Gb limit and have been saved as BigTIFFs, so I need a Delphi unit/library that handles BigTIFF.
Some months are just like the labours of Sisyphus ....
Eric