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Expanding UTM coverage
https://forum.transdem.de/viewtopic.php?f=2&t=698		 Page 2 of 2
Author:  geophil [ 11 Mar 2024 10:38 ]
Post subject:  Re: Expanding UTM coverage
The TransDEM Trainz manual, from page 14, describes using/installing the TransDEM ground textures, including the optional set for ortho-imagery.

Some background can be found in my blog posts on 3D UTM tiles: viewtopic.php?f=2&t=275
Author:  SAR704 [ 12 Mar 2024 10:37 ]
Post subject:  Re: Expanding UTM coverage
Even after reading the description, I am absolutely clueless as to how to even contemplate having terrain textures used as some kind of overlay. Is there any more detailed documentation available that describes it step by step?
Author:  geophil [ 12 Mar 2024 19:19 ]
Post subject:  Re: Expanding UTM coverage
In the "Export to Trainz: Basic files, DEM and ground textures" dialog, enable "custom colour textures" and set the path to "TransDEM128_mapping.txt" (to be found at C:\Program Files\Ziegler-Tools\TransDEM-Ground-Textures for a default installation).

Let me explain the fundamental principle of TransDEM handling Trainz ground textures again:
  • The number of Trainz ground textures is limited to 256 for a classic 10 or 5m baseboard. Ground textures are assigned per ground vertex.
  • Each ground texture is a Trainz asset and defined by KUID.
  • TransDEM comes with two sets of ground textures, the default one with 20 textures, optimized for cartographic maps, and a second one with 128 textures for ortho-imagery. (Different versions of these sets exist for different versions of Trainz.)
  • The default texture set has grid lines (10m), the ortho-image set does not.
  • To get from raster images loaded in TransDEM to Trainz textures, a mapping is required.
  • The mapping is based on RGB colours where one particular colour maps to one particular texture KUID.
  • The colour to texture mapping is defined in the *mapping.txt file.
  • When exporting, TransDEM first resamples the raster image loaded to the baseboard resolution of 720x720pixel or 1440x1440 pixel (10m/5m grid). This is done per baseboard.
  • Then TransDEM reduces the number of colours of the resampled image to the number and values of colours in the *mapping.txt file.
  • This colour reduction is called Colour Quantization and the algorithm used by TransDEM is called Octree.
  • So, after quantization, the raster images processed for export will have exactly the colours defined in the *mapping.txt file.
  • TransDEM then builds the texture lookup table for each baseboard, registers the texture KUIDs in there and assigns a texture index to each ground vertex, based on the quantized colour value of that point.
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