man/man1/obj2mesh.1

.\" RCSid "$Id$"
.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 matinput"
][
.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.
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 mess 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 EXAMPLE
To create a compiled triangle mesh from the scene file mesh.obj:
.IP "" .2i
oconv mesh.obj mesh.rtm
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
gensurf(1), getinfo(1), make(1), obj2rad(1),
oconv(1), rpict(1), rview(1), rtrace(1), xform(1)
Revision:	1.4
Committed:	Tue Dec 9 15:59:06 2003 UTC (20 years, 5 months ago) by greg
Branch:	MAIN
Changes since 1.3:	+1 -1 lines
Log Message:	Fixed RCSid specification
#	User	Rev	Content
1	greg	1.4	.\" RCSid "$Id$"
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	1.3	.B "\-a matinput"
9			][
10	greg	1.1	.B "\-n objlim"
11			][
12			.B "\-r maxres"
13			][
14			.B \-w
15			]
16			[
17			.B "input.obj"
18			[
19			.B "output.rtm"
20			]
21			]
22			.SH DESCRIPTION
23			.I Obj2mesh
24			reads a Wavefront .OBJ file from
25			.I input.obj
26			(or the standard input) and compiles it into a RADIANCE triangle mesh,
27			which is sent to
28			.I output.rtm
29			(or standard output).
30	greg	1.3	Any RADIANCE material descriptions included via one or more
31			.I \-a
32			options will be compiled and stored in the mesh as well.
33	greg	1.1	This mesh may be included in a RADIANCE scene description via the
34			.I mesh
35			primitive, thus:
36			.IP "" .2i
37			mod mesh id
38			.br
39			1+ output.rtm [xform args]
40			.br
41			0
42			.br
43			0
44			.PP
45	greg	1.2	The syntax and semantics are identical to the RADIANCE
46	greg	1.1	.I instance
47	greg	1.3	primitive.
48			If
49			.I mod
50			is "void", then the stored mesh materials will be applied during rendering.
51			Otherwise, the given material will be substituted on
52			all the mesh surfaces.
53	greg	1.1	.PP
54			The
55			.I \-n
56			option specifies the maximum surface set size for
57			each voxel.
58			Larger numbers result in quicker mesh generation needing
59			less memory, but potentially slower rendering.
60			Smaller values may produce faster renderings,
61			since the default number (15) is on the high side to reduce
62			the compiled mesh octree size.
63	greg	1.2	Values below 6 are not recommended, since this is the median
64			valence for a mesh vertex (the number of adjacent faces),
65			and smaller values will result in pointless octree subdivision.
66	greg	1.1	.PP
67			The
68			.I \-r
69			option specifies the maximum octree resolution.
70			This should be greater than or equal to the ratio of the mesh bounding
71			box to the smallest triangle.
72			The default is 16384.
73			.PP
74			The
75			.I \-w
76			option suppresses warnings.
77			.PP
78			Although the mesh file format is binary, it is meant to be portable
79			between machines.
80			The only limitation is that machines with radically different integer
81			sizes will not work together.
82	greg	1.2	.SH DETAILS
83			The following Wavefront statements are understood and compiled by
84			.I obj2mesh.
85			.TP 10n
86			.BI v " x y z"
87			A vertex location, given by its Cartesian coordinates.
88			The final mesh position may of course be modified by
89			the transform arguments given to the
90			.I mesh
91			primitive in the Radiance scene description.
92			.TP
93			.BI vn " dx dy dz"
94			A vertex normal vector, given by its three
95			direction components, which will be normalized by
96			.I obj2mesh.
97			Normals will be interpolated over the mesh
98			during rendering to produce a smooth surface.
99			If no vertex normals are present, the mess will appear tesselated.
100			A zero length normal (i.e., 0 0 0) will generate a syntax error.
101			.TP
102			.BI vt " u v"
103			A local vertex texture coordinate.
104			These coordinates will be interpolated and passed
105			to the "Lu" and "Lv" variables during rendering.
106			Local coordinates can extend over any desired range of values.
107	greg	1.3	.TP
108			.BI usemtl " mname"
109			A material name.
110			The following faces will use the named material, which is
111			taken from the material definitions in the
112			.I \-a
113			input file(s).
114			.TP
115			.BI g " gname"
116			Group association.
117			The following faces are associated with the named group.
118			If no "usemtl" statement has been
119			encountered, the current group is used for the surface material
120			identifier.
121	greg	1.2	.TP
122			.BI f " v1/t1/n1 v2/t2/n2 v3/t3/n3" " .."
123			A polygonal face.
124			Polygon vertices are specified as three indices separated
125			by slashes ('/').
126			The first index is the vertex location, the
127			second index is the local (u,v) texture coordinate, and the
128			third index is the vertex surface normal.
129			Positive indices count from the beginning of the input,
130			where the first vertex position (
131			.I v
132			statement) is numbered 1, and likewise
133			for the first texture coordinate and the first surface normal.
134			Negative indices count backward from the current position in
135			the input, where -1 is the last vertex encountered, -2
136			is the one before that, etc.
137			An index of 0 may be used for the vertex texture or normal to
138			indicate none, or these may be left off entirely.
139			All faces will be broken into triangles in the final mesh.
140			.I Obj2mesh
141			currently makes an unsafe assumption that faces are convex,
142			which may result in odd results if they are not.
143			.PP
144			All other statement types will be ignored on the input.
145			Statements understood by
146			.I obj2rad(1)
147			will be ignored silently; other statements will generate
148			a warning message after translation to indicate how much was missed.
149	greg	1.1	.SH DIAGNOSTICS
150			There are four basic error types reported by obj2mesh:
151			.IP
152			warning - a non-fatal input-related error
153			.IP
154			fatal - an unrecoverable input-related error
155			.IP
156			system - a system-related error
157			.IP
158			internal - a fatal error related to program limitations
159			.IP
160			consistency - a program-caused error
161			.PP
162			Most errors are self-explanatory.
163			However, the following internal errors should be mentioned:
164			.IP "Set overflow in addobject (id)"
165			This error occurs when too many surfaces are close together in a
166			scene.
167	greg	1.2	Sometimes a dense mesh can be accommodated by increasing
168	greg	1.1	the maximum resolution (by powers of two) using the
169			.I \-r
170			option, but usually this error indicates something is wrong.
171			Either too many surfaces are lying right on top of each other,
172			or the bounding cube is inflated from disparate geometry
173			in the input.
174			Chances are, the face number "id" is near
175			those causing the problem.
176			.IP "Hash table overflow in fullnode"
177			This error is caused by too many surfaces, and there is
178			little hope of compiling this mesh.
179			.SH EXAMPLE
180			To create a compiled triangle mesh from the scene file mesh.obj:
181			.IP "" .2i
182			oconv mesh.obj mesh.rtm
183			.SH AUTHOR
184			Greg Ward
185			.SH "SEE ALSO"
186	greg	1.2	gensurf(1), getinfo(1), make(1), obj2rad(1),
187	greg	1.1	oconv(1), rpict(1), rview(1), rtrace(1), xform(1)