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.
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
following 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
normalized.
- 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 vertices
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 formats 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 straightforward. 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)
