man/man1/obj2mesh.1

.\" RCSid "$Id: obj2mesh.1,v 1.7 2004/02/01 22:31:19 greg Exp $"
.TH OBJ2MESH 1 03/11/03 RADIANCE
.SH NAME
obj2mesh - create a compiled RADIANCE mesh file from Wavefront .OBJ input
.SH SYNOPSIS
.B obj2mesh
[
.B "\-a matfile"
][
.B "\-l matlib"
][
.B "\-n objlim"
][
.B "\-r maxres"
][
.B \-w
]
[
.B "input.obj"
[
.B "output.rtm"
]
]
.SH DESCRIPTION
.I Obj2mesh
reads a Wavefront .OBJ file from
.I input.obj
(or the standard input) and compiles it into a RADIANCE triangle mesh,
which is sent to
.I output.rtm
(or standard output).
Any RADIANCE material descriptions included via one or more
.I \-a
options will be compiled and stored in the mesh as well.
If the
.I \-l
option is used to specify a material file, the RADIANCE library
locations are searched.
This mesh may be included in a RADIANCE scene description via the
.I mesh
primitive, thus:
.IP "" .2i
mod mesh id
.br
1+ output.rtm [xform args]
.br
0
.br
0
.PP
The syntax and semantics are identical to the RADIANCE
.I instance
primitive.
If
.I mod
is "void", then the stored mesh materials will be applied during rendering.
Otherwise, the given material will be substituted on
all the mesh surfaces.
.PP
The
.I \-n
option specifies the maximum surface set size for
each voxel.
Larger numbers result in quicker mesh generation needing
less memory, but potentially slower rendering.
Smaller values may produce faster renderings,
since the default number (15) is on the high side to reduce
the compiled mesh octree size.
Values below 6 are not recommended, since this is the median
valence for a mesh vertex (the number of adjacent faces),
and smaller values will result in pointless octree subdivision.
.PP
The
.I \-r
option specifies the maximum octree resolution.
This should be greater than or equal to the ratio of the mesh bounding
box to the smallest triangle.
The default is 16384.
.PP
The
.I \-w
option suppresses warnings.
.PP
Although the mesh file format is binary, it is meant to be portable
between machines.
The only limitation is that machines with radically different integer
sizes will not work together.
.SH DETAILS
The following Wavefront statements are understood and compiled by
.I obj2mesh.
.TP 10n
.BI v " x y z"
A vertex location, given by its Cartesian coordinates.
The final mesh position may of course be modified by
the transform arguments given to the
.I mesh
primitive in the Radiance scene description.
.TP
.BI vn " dx dy dz"
A vertex normal vector, given by its three
direction components, which will be normalized by
.I obj2mesh.
Normals will be interpolated over the mesh
during rendering to produce a smooth surface.
If no vertex normals are present, the mesh will appear tesselated.
A zero length normal (i.e., 0 0 0) will generate a syntax error.
.TP
.BI vt " u v"
A local vertex texture coordinate.
These coordinates will be interpolated and passed
to the "Lu" and "Lv" variables during rendering.
Local coordinates can extend over any desired range of values.
.TP
.BI usemtl " mname"
A material name.
The following faces will use the named material, which is
taken from the material definitions in the
.I \-a
input file(s).
.TP
.BI g " gname"
Group association.
The following faces are associated with the named group.
If no "usemtl" statement has been
encountered, the current group is used for the surface material
identifier.
.TP
.BI f " v1/t1/n1 v2/t2/n2 v3/t3/n3" " .."
A polygonal face.
Polygon vertices are specified as three indices separated
by slashes ('/').
The first index is the vertex location, the
second index is the local (u,v) texture coordinate, and the
third index is the vertex surface normal.
Positive indices count from the beginning of the input,
where the first vertex position (
.I v
statement) is numbered 1, and likewise
for the first texture coordinate and the first surface normal.
Negative indices count backward from the current position in
the input, where -1 is the last vertex encountered, -2
is the one before that, etc.
An index of 0 may be used for the vertex texture or normal to
indicate none, or these may be left off entirely.
All faces will be broken into triangles in the final mesh.
.I Obj2mesh
currently makes an unsafe assumption that faces are convex,
which may result in odd results if they are not.
.PP
All other statement types will be ignored on the input.
Statements understood by
.I obj2rad(1)
will be ignored silently; other statements will generate
a warning message after translation to indicate how much was missed.
.SH DIAGNOSTICS
There are four basic error types reported by obj2mesh:
.IP
warning - a non-fatal input-related error
.IP
fatal - an unrecoverable input-related error
.IP
system - a system-related error
.IP
internal - a fatal error related to program limitations
.IP
consistency - a program-caused error
.PP
Most errors are self-explanatory.
However, the following internal errors should be mentioned:
.IP "Set overflow in addobject (id)"
This error occurs when too many surfaces are close together in a
scene.
Sometimes a dense mesh can be accommodated by increasing
the maximum resolution (by powers of two) using the
.I \-r
option, but usually this error indicates something is wrong.
Either too many surfaces are lying right on top of each other,
or the bounding cube is inflated from disparate geometry
in the input.
Chances are, the face number "id" is near
those causing the problem.
.IP "Hash table overflow in fullnode"
This error is caused by too many surfaces, and there is
little hope of compiling this mesh.
.SH EXAMPLES
To create a compiled triangle mesh from the scene file mesh.obj
using materials from the file mesh.mat:
.IP "" .2i
obj2mesh -a mesh.mat mesh.obj mesh.rtm
.PP
To use local coordinates to place a square tiled image on a mesh object:
.sp
.nf
void colorpict tiled_pat
7 red green blue mytile.pic . frac(Lu) frac(Lv)
0
0

tiled_pat plastic tiled_mat
0
0
5 .9 .9 .9 0 0

tiled_mat mesh tiled_mesh
1 mymesh.rtm
0
0
.fi
.SH ENVIRONMENT
RAYPATH         the directories to search for material files.
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
gensurf(1), getinfo(1), make(1), obj2rad(1),
oconv(1), rpict(1), rvu(1), rtrace(1), xform(1)
Revision:	1.8
Committed:	Fri Apr 23 00:56:27 2004 UTC (20 years, 1 month ago) by greg
Branch:	MAIN
CVS Tags:	rad3R7P2, rad3R7P1, rad3R6, rad3R6P1, rad3R8
Changes since 1.7:	+10 -2 lines
Log Message:	Added -l option to search RAYPATH library locations for material file
#	User	Rev	Content
1	greg	1.8	.\" RCSid "$Id: obj2mesh.1,v 1.7 2004/02/01 22:31:19 greg Exp $"
2	greg	1.1	.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	greg	1.8	.B "\-a matfile"
9			][
10			.B "\-l matlib"
11	greg	1.3	][
12	greg	1.1	.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	greg	1.3	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	greg	1.8	If the
36			.I \-l
37			option is used to specify a material file, the RADIANCE library
38			locations are searched.
39	greg	1.1	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	greg	1.2	The syntax and semantics are identical to the RADIANCE
52	greg	1.1	.I instance
53	greg	1.3	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	greg	1.1	.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	greg	1.2	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	greg	1.1	.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	greg	1.2	.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	greg	1.7	If no vertex normals are present, the mesh will appear tesselated.
106	greg	1.2	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	greg	1.3	.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	greg	1.2	.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	greg	1.1	.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	greg	1.2	Sometimes a dense mesh can be accommodated by increasing
174	greg	1.1	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	greg	1.7	.SH EXAMPLES
186	greg	1.5	To create a compiled triangle mesh from the scene file mesh.obj
187			using materials from the file mesh.mat:
188	greg	1.1	.IP "" .2i
189	greg	1.5	obj2mesh -a mesh.mat mesh.obj mesh.rtm
190	greg	1.7	.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	greg	1.8	.SH ENVIRONMENT
210			RAYPATH the directories to search for material files.
211	greg	1.1	.SH AUTHOR
212			Greg Ward
213			.SH "SEE ALSO"
214	greg	1.2	gensurf(1), getinfo(1), make(1), obj2rad(1),
215	greg	1.6	oconv(1), rpict(1), rvu(1), rtrace(1), xform(1)