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.\" RCSid "$Id: obj2mesh.1,v 1.9 2007/07/12 14:58:52 greg Exp $" |
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.TH OBJ2MESH 1 03/11/03 RADIANCE |
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.SH NAME |
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obj2mesh - create a compiled RADIANCE mesh file from Wavefront .OBJ input |
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.SH SYNOPSIS |
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.B obj2mesh |
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[ |
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.B "\-a matfile" |
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][ |
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.B "\-l matlib" |
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][ |
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.B "\-n objlim" |
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][ |
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.B "\-r maxres" |
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][ |
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.B \-w |
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] |
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[ |
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.B "input.obj" |
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[ |
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.B "output.rtm" |
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] |
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] |
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.SH DESCRIPTION |
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.I Obj2mesh |
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reads a Wavefront .OBJ file from |
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.I input.obj |
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(or the standard input) and compiles it into a RADIANCE triangle mesh, |
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which is sent to |
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.I output.rtm |
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(or standard output). |
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Any RADIANCE material descriptions included via one or more |
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.I \-a |
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options will be compiled and stored in the mesh as well. |
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If the |
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.I \-l |
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option is used to specify a material file, the RADIANCE library |
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locations are searched. |
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This mesh may be included in a RADIANCE scene description via the |
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.I mesh |
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primitive, thus: |
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.IP "" .2i |
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mod mesh id |
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.br |
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1+ output.rtm [xform args] |
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.br |
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0 |
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.br |
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0 |
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.PP |
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The syntax and semantics are identical to the RADIANCE |
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.I instance |
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primitive. |
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If |
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.I mod |
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is "void", then the stored mesh materials will be applied during rendering. |
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Otherwise, the given material will be substituted on |
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all the mesh surfaces. |
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.PP |
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The |
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.I \-n |
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option specifies the maximum surface set size for |
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each voxel. |
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Larger numbers result in quicker mesh generation, |
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but potentially slower rendering. |
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Values below 6 are not recommended, since this is the median |
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valence for a mesh vertex (the number of adjacent faces), |
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and smaller values will result in pointless octree subdivision. |
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The default setting is 9. |
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.PP |
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The |
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.I \-r |
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option specifies the maximum octree resolution. |
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This should be greater than or equal to the ratio of the mesh bounding |
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box to the smallest triangle. |
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The default is 16384. |
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.PP |
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The |
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.I \-w |
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option suppresses warnings. |
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.PP |
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Although the mesh file format is binary, it is meant to be portable |
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between machines. |
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The only limitation is that machines with radically different integer |
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sizes will not work together. |
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.SH DETAILS |
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The following Wavefront statements are understood and compiled by |
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.I obj2mesh. |
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.TP 10n |
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.BI v " x y z" |
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A vertex location, given by its Cartesian coordinates. |
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The final mesh position may of course be modified by |
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the transform arguments given to the |
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.I mesh |
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primitive in the Radiance scene description. |
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.TP |
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.BI vn " dx dy dz" |
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A vertex normal vector, given by its three |
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direction components, which will be normalized by |
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.I obj2mesh. |
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Normals will be interpolated over the mesh |
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during rendering to produce a smooth surface. |
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If no vertex normals are present, the mesh will appear tesselated. |
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A zero length normal (i.e., 0 0 0) will generate a syntax error. |
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.TP |
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.BI vt " u v" |
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A local vertex texture coordinate. |
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These coordinates will be interpolated and passed |
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to the "Lu" and "Lv" variables during rendering. |
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Local coordinates can extend over any desired range of values. |
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.TP |
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.BI usemtl " mname" |
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A material name. |
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The following faces will use the named material, which is |
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taken from the material definitions in the |
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.I \-a |
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input file(s). |
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.TP |
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.BI g " gname" |
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Group association. |
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The following faces are associated with the named group. |
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If no "usemtl" statement has been |
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encountered, the current group is used for the surface material |
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identifier. |
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.TP |
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.BI f " v1/t1/n1 v2/t2/n2 v3/t3/n3" " .." |
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A polygonal face. |
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Polygon vertices are specified as three indices separated |
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by slashes ('/'). |
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The first index is the vertex location, the |
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second index is the local (u,v) texture coordinate, and the |
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third index is the vertex surface normal. |
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Positive indices count from the beginning of the input, |
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where the first vertex position ( |
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.I v |
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statement) is numbered 1, and likewise |
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for the first texture coordinate and the first surface normal. |
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Negative indices count backward from the current position in |
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the input, where \-1 is the last vertex encountered, \-2 |
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is the one before that, etc. |
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An index of 0 may be used for the vertex texture or normal to |
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indicate none, or these may be left off entirely. |
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All faces will be broken into triangles in the final mesh. |
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.I Obj2mesh |
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currently makes an unsafe assumption that faces are convex, |
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which may result in odd results if they are not. |
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.PP |
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All other statement types will be ignored on the input. |
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Statements understood by |
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.I obj2rad(1) |
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will be ignored silently; other statements will generate |
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a warning message after translation to indicate how much was missed. |
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.SH DIAGNOSTICS |
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There are four basic error types reported by obj2mesh: |
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.IP |
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warning - a non-fatal input-related error |
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.IP |
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fatal - an unrecoverable input-related error |
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.IP |
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system - a system-related error |
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.IP |
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internal - a fatal error related to program limitations |
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.IP |
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consistency - a program-caused error |
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.PP |
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Most errors are self-explanatory. |
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However, the following internal errors should be mentioned: |
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.IP "Set overflow in addobject (id)" |
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This error occurs when too many surfaces are close together in a |
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scene. |
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Sometimes a dense mesh can be accommodated by increasing |
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the maximum resolution (by powers of two) using the |
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.I \-r |
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option, but usually this error indicates something is wrong. |
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Either too many surfaces are lying right on top of each other, |
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or the bounding cube is inflated from disparate geometry |
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in the input. |
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Chances are, the face number "id" is near |
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those causing the problem. |
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.IP "Hash table overflow in fullnode" |
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This error is caused by too many surfaces, and there is |
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little hope of compiling this mesh. |
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.SH EXAMPLES |
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To create a compiled triangle mesh from the scene file mesh.obj |
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using materials from the file mesh.mat: |
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.IP "" .2i |
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obj2mesh \-a mesh.mat mesh.obj mesh.rtm |
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.PP |
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To use local coordinates to place a square tiled image on a mesh object: |
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.sp |
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.nf |
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void colorpict tiled_pat |
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7 red green blue mytile.pic . frac(Lu) frac(Lv) |
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0 |
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0 |
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|
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tiled_pat plastic tiled_mat |
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0 |
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0 |
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5 .9 .9 .9 0 0 |
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|
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tiled_mat mesh tiled_mesh |
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1 mymesh.rtm |
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0 |
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0 |
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.fi |
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.SH ENVIRONMENT |
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RAYPATH the directories to search for material files. |
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.SH AUTHOR |
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Greg Ward |
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.SH "SEE ALSO" |
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gensurf(1), getinfo(1), make(1), obj2rad(1), |
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oconv(1), rpict(1), rvu(1), rtrace(1), xform(1) |
