TMESH2RAD(1) General Commands Manual TMESH2RAD(1)
NAME
tmesh2rad - convert a triangular mesh to a RADIANCE scene description
SYNOPSIS
tmesh2rad [ -o obj ][ -m mat ][ -p pat ] [ input .. ]
DESCRIPTION
Tmesh2rad converts one or more triangle-mesh files to a RADIANCE scene description. The -o option may be used to assign a default object
name. The single letter "T" is used if no name is given on the command line or in the file. The -m option may be used to assign a default
material name. The non-material "void" is used as a default if none is given on the command line or in the file. The -p option may be
used to assign a default picture for a surface pattern. If none is given on the command line or in the file, the surface will not have an
associated pattern.
FILE FORMAT
A triangle-mesh is a free-format ASCII file composed of the following eight primitive types. Each primitive is begun with a single, white-
space-delimited letter:
# Comment Whatever follows up until the end of line is passed as a comment to the output. Note that there must be at least one space or
tab following the pound-sign.
o name The white-space-delimited string name is used as a prefix for all following output triangles.
m material
The white-space-delimited string material is used as the modifier name for all following output triangles.
p picture The white-space-delimited string picture is used as the name of the RADIANCE picture file to be used as a pattern for all follow-
ing output triangles with properly defined vertices. (See i primitive below.)
v id x y z
Defines the vertex id with 3-dimensional coordinates x, y and z. The identifier, id must be some small, non-negative integer
value. If the same integer is used for a later vertex definition, this definition will be lost, though any triangles using the
vertex prior to its redefinition will be unaffected.
n nx ny nz
Defines a surface normal vector with the 3-dimensional components nx, ny and nz. This vector will be associated with the most
recently defined vertex, and is often placed on the same line as the vertex definition for clarity. The vector need not be nor-
malized.
i u v Defines a picture index for the most recently defined vertex. The u value will be used to lookup the horizontal pixel coordinate
in the currently defined picture. The v value will be used to lookup the vertical pixel coordinate. (See the RADIANCE reference
manual for details on picture coordinate values.) As with associated surface normals, picture indices are interpolated using
barycentric coordinates based on the triangle vertices. If these coordinates are calculated correctly, this should result in a
smooth mapping of a pattern onto the surface mesh.
t id1 id2 id3
Create a triangle connecting the three vertices identified by id1, id2 and id3. The right-hand rule is used to determine the
default surface normal orientation, and this should not be too far from the associated vertex normals (if any). All three ver-
tices must have an associated normal if the triangle is to be smoothed. If a picture file is defined and all three vertices have
pattern indices associated with them, then this picture will be used as a pattern to modify the triangle's color.
We realize there are many similar T-mesh file formats in existence, and that it would have been just as easy to support one of these for-
mats directly. The disadvantage to supporting an existing format is that conversion from other formats might prove difficult. It was our
hope to provide a "greatest common multiple" format that would support all similar T-mesh formats, rather than supporting WaveFront's .obj
format (for example) and being unable to associate a pattern with an object. Converting from other formats should be relatively straight-
forward. In many cases, an awk(1), rcalc(1) or even a sed(1) script should be sufficient.
EXAMPLE
Here is an example T-mesh file:
# Our object name:
o test_object
# Our material:
m puce
# Our vertices:
v 1 10 15 5
v 2 10 -15 5
v 3 0 -15 0
v 4 -10 15 -5
# Two triangles joined together:
t 1 2 3
t 2 3 4
Which generates the following output:
## T-mesh read from: <stdin>
# Our material:
# Our vertices:
# Two triangles joined together:
puce polygon test_object.1
0
0
9
10 15 5
10 -15 5
0 -15 0
puce polygon test_object.2
0
0
9
10 -15 5
0 -15 0
-10 15 -5
Here is another example:
# A partial cylinder:
m BluePlastic
v 1 -14.673 -3.119 50 n -0.95677 -0.203374 1.17936e-10
v 2 -12.136 -8.817 -50 n -0.791363 -0.574922 4.84915e-10
v 3 -12.136 -8.817 50 n -0.791363 -0.574922 4.84915e-10
t 1 2 3
m OrangePlastic
v 1 -7.501 -12.991 50 n -0.549094 -0.812427 -1.45812e-09
v 2 -12.136 -8.817 50 n -0.791363 -0.574922 4.84915e-10
v 3 -12.136 -8.817 -50 n -0.791363 -0.574922 4.84915e-10
t 1 2 3
m BluePlastic
v 1 -1.568 -14.918 50 n -0.171094 -0.965568 -5.69788e-09
v 2 -7.501 -12.991 50 n -0.549094 -0.812427 -1.45812e-09
v 3 -7.501 -12.991 -50 n -0.429001 -0.881759 -3.6502e-09
t 1 2 3
Note that the same three vertices were used repeatedly, and intermingled with the triangle definitions.
AUTHOR
Greg Ward
BUGS
Triangle smoothing doesn't work very well for glass or trans material types in Radiance, since textures cause distorted transmission
through these materials. It is best to use the dielectric material type if smooth transmission is desired.
SEE ALSO
arch2rad(1), awk(1), ies2rad(1), thf2rad(1), oconv(1), rcalc(1), sed(1), xform(1)
RADIANCE
3/18/96 TMESH2RAD(1)