[GRASS-dev] convert 3D polygons or Tins to a DEM?

[Maciej Sieczka]

Markus Neteler pisze:
> Hi,
> 
> can we convert 3D polygons or tins to a DEM? Possibly a job for
> v.to.rast...

I did it this way:

1. Obtain the tin as a 3d shapefile with triangle edges as lines. This 
can be done from ArcInfo/ArcGIS.
2. Translate each 3d line into 3d points, one point per cell in 
accordance with current resolution.
3. Rasterize these 3 points.
4. r.surf.nnabthy alg=l interpolates a raster using linear 
triangulation, recreating the TIN as a raster.

An un-polished shell code implementing step 3 is attached. Maybe you'll 
find it usefull till no better solution in GRASS.

I don't rememeber why, but I rasterised the breaklines and main triangle 
edges separately (you can separate them based on their attributes), then 
patched rasters. Can't remember some details no; it's been some time. 
There are comments in the script.

Maciek
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