I just put my first-effort GRASS to VRML translator
on moon. Now you can share any (small) GRASS terrain map
with your friends around the Web, in all it's "3D" glory!
ftp://moon.cecer.army.mil/pub/grass/incoming/Paint/p.vrml1.0.tar
Here's the README:
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28 Aug 1996
This is a preliminary release of "p.vrml", a GRASS program
to output GRASS data in the format of Virtual Reality Modeling
Language (VRML).
For further information about VRML and available viewers
for various platforms, see:
http://vag.vrml.org/
http://www.sdsc.edu/vrml/
This version only outputs raster maps in VRML 1.0 format.
The newer VRML 2.0 format will be more efficient for geographic
applications, as it introduces an "ElevationGrid" node so that
only the elevation points will have to be written instead
of the whole geometry. The vast majority of VRML viewers
currently only support VRML 1.0.
Future plans for this module are to allow draping of sites
objects and vector files and using the new sites format
available in floating point GRASS to embed WWW links into
site objects. It will also be upgraded to support VRML 2.0
and will allow entering multiple preset "views" using the
existing GRASS 3d_view file format.
Other possible additions:
o Allow animation of elevation, color, or sites based on
user interaction.
o Degradation of the raster to produce TINs for better
performance.
This code should compile on any GRASS platform with either
GRASS 4.1 or floating point GRASS.
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Usage:
p.vrml elev=name [color=name] [exag=value] output=name
Parameters:
elev Name of elevation file.
color Name of color file.
exag exaggeration
default: 1.0
output Name of new VRML file.
"elev" is a raster file to use for surface topography.
"color" (optional) raster file to use for surface color.
"exag" is an exaggeration factor for the vertical dimension.
"output" is a name for the new VRML file. If the extension
"wrl" (world) is not present in the name, it will be added.
WARNING: VRML is not well suited for large geometrys which can
result from even a small geographic region. Most viewers
seem to bog down with more than 12,000 polygons, depending
on your hardware & specific viewer. Each grid cell results
in two polygons, so a reasonable size region would be
something less than about 75x75. For improved performance
and smaller file size, leave off a color map. Since VRML
is ascii text, gzip works very well to significantly
compress file size.
BUGS: Currently the region is transformed to a unit size, so
real geographic location is lost. Side effects when
working in a lat-lon location are that besides general
distortion due to projection, a very small exaggeration
factor (on order of .001) must be used to compensate for
vertical units expected to be the same as map units.
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Bill Brown e-mail: brown@gis.uiuc.edu
220 Davenport Hall - MC 150 phone: (217) 333-5077
607 S. Mathews
Urbana, IL 61801
http://www.cecer.army.mil/grass/viz/VIZ.html
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