Shading with Blender

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Blender can produce stunning shaded illumination maps using ray-tracers. It knows nothing about projections but once we get the shade grayscale image we can use it in GMT. Here’s an example (not fully comprehensible, I know)

using GMT

Gib = grdcut("@earth_relief_15s", region="-15/4/34/45");
color = gdaldem(Gib, "color-relief"; color="earth");
Iblend = gmtread("iberia_rt_s15.png");                # ALMOST ALL WORK LIES HERE
Iburn = blendimg!(color, Iblend, mode="LinearBurn", new=true);
Ib = blendimg!(Iburn, Iblend, mode="Screen", new=true);
viz(Ib, proj=:guess, coast=1)

I have created this little tutorial that has some more informations to support the involved mechanics
https://www.generic-mapping-tools.org/GMTjl_doc/tutorials/blender_shading/blender_rt/

GMTjl_j-or8
GMTjl_j-or81904×1375 475 KB

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Bless the projection, a post about Blender!

I’m going to try this. I’ve used GMT to prepare tiff’s to do this in Blender, but not with Julia. Hope it’s Ok with some Q&A, even though it’s a showcase(?)

Just using GMT to prepare grids to import to Blender for further work is also interesting.

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GMT can also just be used to prepare heightmaps for use in Blender.

Take your grid and use grdmath’s NORM function;

  • For UInt16:

    $ gmt grdmath dtm.tif NORM 2 16 POW MUL = heightmap.tif=gdal:GTIFF

  • For UInt32:

    $ gmt grdmath dtm.tif NORM 2 32 POW MUL = heightmap.tif=gdal:GTIFF

Why anyone would ever need UInt32, I don’t know (this gives 2^32 = 4.29E9 levels)
UInt16 (2^16 = 65535) is also a very high number, but Byte/Int8 (2^8 = 255) may be too low. If your terrains elevation difference is 1000’s of meters, it’ll not be enough levels. (Is byte the same as UInt8?)