Jean Roc wrote:
I was thinking about using r3.in.ascii and then r.to.rast3
eg http://grass.osgeo.org/wiki/Help_with_3D
but it doesn't seems to be the right thing to do on a large
scale (150km²) due to potential multiple top/bottom crossing
of the generated layers.
...
Your screenshots are exactly the kind of data visualization
I'm seeking to obtain.
see Helena's GRASS 4 screenshots near the end of this page:
http://grass.osgeo.org/screenshots/viz.php
http://skagit.meas.ncsu.edu/~helena/gmslab/viz/ches.html
GRASS's own NVIZ has support for custom isosurfaces and multiple
cutting planes.
this thread might interest you:
http://thread.gmane.org/gmane.comp.gis.grass.user/12869
Hamish