| 1 |
.\" RCSid "$Id: obj2mesh.1,v 1.7 2004/02/01 22:31:19 greg Exp $" |
| 2 |
.TH OBJ2MESH 1 03/11/03 RADIANCE |
| 3 |
.SH NAME |
| 4 |
obj2mesh - create a compiled RADIANCE mesh file from Wavefront .OBJ input |
| 5 |
.SH SYNOPSIS |
| 6 |
.B obj2mesh |
| 7 |
[ |
| 8 |
.B "\-a matfile" |
| 9 |
][ |
| 10 |
.B "\-l matlib" |
| 11 |
][ |
| 12 |
.B "\-n objlim" |
| 13 |
][ |
| 14 |
.B "\-r maxres" |
| 15 |
][ |
| 16 |
.B \-w |
| 17 |
] |
| 18 |
[ |
| 19 |
.B "input.obj" |
| 20 |
[ |
| 21 |
.B "output.rtm" |
| 22 |
] |
| 23 |
] |
| 24 |
.SH DESCRIPTION |
| 25 |
.I Obj2mesh |
| 26 |
reads a Wavefront .OBJ file from |
| 27 |
.I input.obj |
| 28 |
(or the standard input) and compiles it into a RADIANCE triangle mesh, |
| 29 |
which is sent to |
| 30 |
.I output.rtm |
| 31 |
(or standard output). |
| 32 |
Any RADIANCE material descriptions included via one or more |
| 33 |
.I \-a |
| 34 |
options will be compiled and stored in the mesh as well. |
| 35 |
If the |
| 36 |
.I \-l |
| 37 |
option is used to specify a material file, the RADIANCE library |
| 38 |
locations are searched. |
| 39 |
This mesh may be included in a RADIANCE scene description via the |
| 40 |
.I mesh |
| 41 |
primitive, thus: |
| 42 |
.IP "" .2i |
| 43 |
mod mesh id |
| 44 |
.br |
| 45 |
1+ output.rtm [xform args] |
| 46 |
.br |
| 47 |
0 |
| 48 |
.br |
| 49 |
0 |
| 50 |
.PP |
| 51 |
The syntax and semantics are identical to the RADIANCE |
| 52 |
.I instance |
| 53 |
primitive. |
| 54 |
If |
| 55 |
.I mod |
| 56 |
is "void", then the stored mesh materials will be applied during rendering. |
| 57 |
Otherwise, the given material will be substituted on |
| 58 |
all the mesh surfaces. |
| 59 |
.PP |
| 60 |
The |
| 61 |
.I \-n |
| 62 |
option specifies the maximum surface set size for |
| 63 |
each voxel. |
| 64 |
Larger numbers result in quicker mesh generation needing |
| 65 |
less memory, but potentially slower rendering. |
| 66 |
Smaller values may produce faster renderings, |
| 67 |
since the default number (15) is on the high side to reduce |
| 68 |
the compiled mesh octree size. |
| 69 |
Values below 6 are not recommended, since this is the median |
| 70 |
valence for a mesh vertex (the number of adjacent faces), |
| 71 |
and smaller values will result in pointless octree subdivision. |
| 72 |
.PP |
| 73 |
The |
| 74 |
.I \-r |
| 75 |
option specifies the maximum octree resolution. |
| 76 |
This should be greater than or equal to the ratio of the mesh bounding |
| 77 |
box to the smallest triangle. |
| 78 |
The default is 16384. |
| 79 |
.PP |
| 80 |
The |
| 81 |
.I \-w |
| 82 |
option suppresses warnings. |
| 83 |
.PP |
| 84 |
Although the mesh file format is binary, it is meant to be portable |
| 85 |
between machines. |
| 86 |
The only limitation is that machines with radically different integer |
| 87 |
sizes will not work together. |
| 88 |
.SH DETAILS |
| 89 |
The following Wavefront statements are understood and compiled by |
| 90 |
.I obj2mesh. |
| 91 |
.TP 10n |
| 92 |
.BI v " x y z" |
| 93 |
A vertex location, given by its Cartesian coordinates. |
| 94 |
The final mesh position may of course be modified by |
| 95 |
the transform arguments given to the |
| 96 |
.I mesh |
| 97 |
primitive in the Radiance scene description. |
| 98 |
.TP |
| 99 |
.BI vn " dx dy dz" |
| 100 |
A vertex normal vector, given by its three |
| 101 |
direction components, which will be normalized by |
| 102 |
.I obj2mesh. |
| 103 |
Normals will be interpolated over the mesh |
| 104 |
during rendering to produce a smooth surface. |
| 105 |
If no vertex normals are present, the mesh will appear tesselated. |
| 106 |
A zero length normal (i.e., 0 0 0) will generate a syntax error. |
| 107 |
.TP |
| 108 |
.BI vt " u v" |
| 109 |
A local vertex texture coordinate. |
| 110 |
These coordinates will be interpolated and passed |
| 111 |
to the "Lu" and "Lv" variables during rendering. |
| 112 |
Local coordinates can extend over any desired range of values. |
| 113 |
.TP |
| 114 |
.BI usemtl " mname" |
| 115 |
A material name. |
| 116 |
The following faces will use the named material, which is |
| 117 |
taken from the material definitions in the |
| 118 |
.I \-a |
| 119 |
input file(s). |
| 120 |
.TP |
| 121 |
.BI g " gname" |
| 122 |
Group association. |
| 123 |
The following faces are associated with the named group. |
| 124 |
If no "usemtl" statement has been |
| 125 |
encountered, the current group is used for the surface material |
| 126 |
identifier. |
| 127 |
.TP |
| 128 |
.BI f " v1/t1/n1 v2/t2/n2 v3/t3/n3" " .." |
| 129 |
A polygonal face. |
| 130 |
Polygon vertices are specified as three indices separated |
| 131 |
by slashes ('/'). |
| 132 |
The first index is the vertex location, the |
| 133 |
second index is the local (u,v) texture coordinate, and the |
| 134 |
third index is the vertex surface normal. |
| 135 |
Positive indices count from the beginning of the input, |
| 136 |
where the first vertex position ( |
| 137 |
.I v |
| 138 |
statement) is numbered 1, and likewise |
| 139 |
for the first texture coordinate and the first surface normal. |
| 140 |
Negative indices count backward from the current position in |
| 141 |
the input, where -1 is the last vertex encountered, -2 |
| 142 |
is the one before that, etc. |
| 143 |
An index of 0 may be used for the vertex texture or normal to |
| 144 |
indicate none, or these may be left off entirely. |
| 145 |
All faces will be broken into triangles in the final mesh. |
| 146 |
.I Obj2mesh |
| 147 |
currently makes an unsafe assumption that faces are convex, |
| 148 |
which may result in odd results if they are not. |
| 149 |
.PP |
| 150 |
All other statement types will be ignored on the input. |
| 151 |
Statements understood by |
| 152 |
.I obj2rad(1) |
| 153 |
will be ignored silently; other statements will generate |
| 154 |
a warning message after translation to indicate how much was missed. |
| 155 |
.SH DIAGNOSTICS |
| 156 |
There are four basic error types reported by obj2mesh: |
| 157 |
.IP |
| 158 |
warning - a non-fatal input-related error |
| 159 |
.IP |
| 160 |
fatal - an unrecoverable input-related error |
| 161 |
.IP |
| 162 |
system - a system-related error |
| 163 |
.IP |
| 164 |
internal - a fatal error related to program limitations |
| 165 |
.IP |
| 166 |
consistency - a program-caused error |
| 167 |
.PP |
| 168 |
Most errors are self-explanatory. |
| 169 |
However, the following internal errors should be mentioned: |
| 170 |
.IP "Set overflow in addobject (id)" |
| 171 |
This error occurs when too many surfaces are close together in a |
| 172 |
scene. |
| 173 |
Sometimes a dense mesh can be accommodated by increasing |
| 174 |
the maximum resolution (by powers of two) using the |
| 175 |
.I \-r |
| 176 |
option, but usually this error indicates something is wrong. |
| 177 |
Either too many surfaces are lying right on top of each other, |
| 178 |
or the bounding cube is inflated from disparate geometry |
| 179 |
in the input. |
| 180 |
Chances are, the face number "id" is near |
| 181 |
those causing the problem. |
| 182 |
.IP "Hash table overflow in fullnode" |
| 183 |
This error is caused by too many surfaces, and there is |
| 184 |
little hope of compiling this mesh. |
| 185 |
.SH EXAMPLES |
| 186 |
To create a compiled triangle mesh from the scene file mesh.obj |
| 187 |
using materials from the file mesh.mat: |
| 188 |
.IP "" .2i |
| 189 |
obj2mesh -a mesh.mat mesh.obj mesh.rtm |
| 190 |
.PP |
| 191 |
To use local coordinates to place a square tiled image on a mesh object: |
| 192 |
.sp |
| 193 |
.nf |
| 194 |
void colorpict tiled_pat |
| 195 |
7 red green blue mytile.pic . frac(Lu) frac(Lv) |
| 196 |
0 |
| 197 |
0 |
| 198 |
|
| 199 |
tiled_pat plastic tiled_mat |
| 200 |
0 |
| 201 |
0 |
| 202 |
5 .9 .9 .9 0 0 |
| 203 |
|
| 204 |
tiled_mat mesh tiled_mesh |
| 205 |
1 mymesh.rtm |
| 206 |
0 |
| 207 |
0 |
| 208 |
.fi |
| 209 |
.SH ENVIRONMENT |
| 210 |
RAYPATH the directories to search for material files. |
| 211 |
.SH AUTHOR |
| 212 |
Greg Ward |
| 213 |
.SH "SEE ALSO" |
| 214 |
gensurf(1), getinfo(1), make(1), obj2rad(1), |
| 215 |
oconv(1), rpict(1), rvu(1), rtrace(1), xform(1) |
