For information on the port of r3.showdspf from IrisGL to OpenGL browse the 
document r3.showdspf_opengl_mods.html

Ken Sakai
Lockheed Martin
4-3-00

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r3.showdspf is not built by default in GRASS 6.2. If you want to build it you
need to ./configure GRASS --with-glw support and run 'make' manually from the
raster3d/r3.showdspf/ source directory.

AFAIK it is the only thing in GRASS 6.2 which uses GLw:
  http://article.gmane.org/gmane.comp.gis.grass.devel/19079


Hamish Bowman
15 Aug 2007