man/man1/robjutil.1

.\" RCSid "$Id: robjutil.1,v 1.3 2020/04/02 20:50:59 greg Exp $"
.TH ROBJUTIL 1 3/31/20 RADIANCE
.SH NAME
robjutil - operate on Wavefront .OBJ file
.SH SYNOPSIS
.B robjutil
[
.B +/-r
][
.B +/-v
][
.B +/-t
][
.B +/-n
][
.B "+/-m mname"
][
.B "+/-g gname"
][
.B "-c epsilon"
][
.B "-x 'xf spec'"
]
[
.B input.obj ..
]
.SH DESCRIPTION
.I Robjutil
reads and manipulates a Wavefront .OBJ file, removing degenerate and
duplicate faces.
If the
.I +r
option is specified, a Radiance scene description
will be produced on the standard output.
If
.I -r
is given, a modified .OBJ file will be sent to the standard output.
This is the default, and is
typically more useful, since surface normals are better handled by the
.I obj2rad(1)
and
.I obj2mesh(1)
converters.
The latter also preserves local texture coordinates for mapping materials.
The
.I +v
option turns on verbose progress reports.
.PP
The
.I \-t
option tells
.I robjutil
to remove texture coordinates from the input.
The
.I \-n
option will cause all surface normals to be removed.
.PP
The
.I "\-m mname"
option tells
.I robjutil
to remove all faces that use the material
.I mname.
Multiple
.I \-m
options may be given, each with a single (unique) material name.
Alternatively, the
.I "+m mname"
option may be used to specify a material one wishes to keep, discarding the rest.
Multiple
.I +m
options will keep all the named materials.
The
.I \-m
and
.I \+m
options are mutually exclusive.
Similarly, the
.I "\-g gname"
option says to remove all faces belonging to the group
.I gname,
and multiple
.I \-g
options may be given.
There is also a
.I +g
option to save just the named group(s).
.PP
The
.I "\-c epsilon"
option tells
.I robjutil
to coalesce vertices that are within the given epsilon.
This is useful to improve the connectivity of models that were produced
in a sloppy conversion process from independent polygons.
When producing a Radiance file via the
.I +r
option, there will be no savings in the output size, but there can be
a benefit in reducing the number of "cracks" in the resulting geometry,
at least for triangle mesh input.
.I Robjutil
does not attempt to break up non-planar polygons into triangles,
which is usually not a problem for .OBJ output, but may be for Radiance
scene descriptions (+r).
.PP
The
.I \-x
option may be used to specify a final transform to apply to all
coordinates in the file before output.
This specification must be contained in a single quoted word and
match the standard arguments used by
.I xform(1),
except that the
.I \-a
option is not supported for creating arrays of objects.
Also, any scaling factors do not affect the epsilon value given for
coalescing vertices, as this operation is applied prior to the transform,
even if
.I \-c
appears later in the command line.
.SH EXAMPLES
To remove degenerate and duplicate faces from "orig.obj" and write to "final.rad":
.IP "" .2i
robjutil +r orig.obj > final.rad
.PP
To convert the same file, preserving surface normal interpolation:
.IP "" .2i
robjutil orig.obj | obj2rad > withnormals.rad
.PP
To extract only the groups "cat" and "bell" from the file "kitty.obj" and
write to a Radiance triangle mesh using materials from "kitty.mat":
.IP "" .2i
robjutil +g cat +g bell kitty.obj | obj2mesh -a kitty.mat > kitty.rtm
.PP
To rotate the scene 90 degrees about the Y-axis and scale by 10:
.IP "" .2i
robjutil -x "-ry 90 -s 10" orig.obj > transformed.obj
.SH NOTES
The .OBJ output of
.I robjutil
uses relative indices, so files it produces may be concatenated
on the input of other tools such as
.I obj2rad
and
.I obj2mesh
by piping from
.I cat(1)
or similar.
This offers a convenient way to separate geometry from a single .OBJ
input, manipulate it in some way, then recombine during conversion.
.PP
Unlike
.I obj2rad
and
.I obj2mesh,
.I robjutil
with the
.I +r
option will not substitute the group name for a material id if no
.I usemtl
statements are found on the input.
Instead, it will assign each surface the material
.I DEFAULT_MATERIAL.
Since it is possible to use the
.I +/-g
option to select groups to include or exclude on output, it is
still possible to assign materials by group manually.
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
cat(1), obj2mesh(1), obj2rad(1) oconv(1), xform(1)
Revision:	1.4
Committed:	Fri Apr 3 02:32:58 2020 UTC (5 years, 2 months ago) by greg
Branch:	MAIN
Changes since 1.3:	+32 -2 lines
Log Message:	Added some application notes
#	Content
1	.\" RCSid "$Id: robjutil.1,v 1.3 2020/04/02 20:50:59 greg Exp $"
2	.TH ROBJUTIL 1 3/31/20 RADIANCE
3	.SH NAME
4	robjutil - operate on Wavefront .OBJ file
5	.SH SYNOPSIS
6	.B robjutil
7	[
8	.B +/-r
9	][
10	.B +/-v
11	][
12	.B +/-t
13	][
14	.B +/-n
15	][
16	.B "+/-m mname"
17	][
18	.B "+/-g gname"
19	][
20	.B "-c epsilon"
21	][
22	.B "-x 'xf spec'"
23	]
24	[
25	.B input.obj ..
26	]
27	.SH DESCRIPTION
28	.I Robjutil
29	reads and manipulates a Wavefront .OBJ file, removing degenerate and
30	duplicate faces.
31	If the
32	.I +r
33	option is specified, a Radiance scene description
34	will be produced on the standard output.
35	If
36	.I -r
37	is given, a modified .OBJ file will be sent to the standard output.
38	This is the default, and is
39	typically more useful, since surface normals are better handled by the
40	.I obj2rad(1)
41	and
42	.I obj2mesh(1)
43	converters.
44	The latter also preserves local texture coordinates for mapping materials.
45	The
46	.I +v
47	option turns on verbose progress reports.
48	.PP
49	The
50	.I \-t
51	option tells
52	.I robjutil
53	to remove texture coordinates from the input.
54	The
55	.I \-n
56	option will cause all surface normals to be removed.
57	.PP
58	The
59	.I "\-m mname"
60	option tells
61	.I robjutil
62	to remove all faces that use the material
63	.I mname.
64	Multiple
65	.I \-m
66	options may be given, each with a single (unique) material name.
67	Alternatively, the
68	.I "+m mname"
69	option may be used to specify a material one wishes to keep, discarding the rest.
70	Multiple
71	.I +m
72	options will keep all the named materials.
73	The
74	.I \-m
75	and
76	.I \+m
77	options are mutually exclusive.
78	Similarly, the
79	.I "\-g gname"
80	option says to remove all faces belonging to the group
81	.I gname,
82	and multiple
83	.I \-g
84	options may be given.
85	There is also a
86	.I +g
87	option to save just the named group(s).
88	.PP
89	The
90	.I "\-c epsilon"
91	option tells
92	.I robjutil
93	to coalesce vertices that are within the given epsilon.
94	This is useful to improve the connectivity of models that were produced
95	in a sloppy conversion process from independent polygons.
96	When producing a Radiance file via the
97	.I +r
98	option, there will be no savings in the output size, but there can be
99	a benefit in reducing the number of "cracks" in the resulting geometry,
100	at least for triangle mesh input.
101	.I Robjutil
102	does not attempt to break up non-planar polygons into triangles,
103	which is usually not a problem for .OBJ output, but may be for Radiance
104	scene descriptions (+r).
105	.PP
106	The
107	.I \-x
108	option may be used to specify a final transform to apply to all
109	coordinates in the file before output.
110	This specification must be contained in a single quoted word and
111	match the standard arguments used by
112	.I xform(1),
113	except that the
114	.I \-a
115	option is not supported for creating arrays of objects.
116	Also, any scaling factors do not affect the epsilon value given for
117	coalescing vertices, as this operation is applied prior to the transform,
118	even if
119	.I \-c
120	appears later in the command line.
121	.SH EXAMPLES
122	To remove degenerate and duplicate faces from "orig.obj" and write to "final.rad":
123	.IP "" .2i
124	robjutil +r orig.obj > final.rad
125	.PP
126	To convert the same file, preserving surface normal interpolation:
127	.IP "" .2i
128	robjutil orig.obj \| obj2rad > withnormals.rad
129	.PP
130	To extract only the groups "cat" and "bell" from the file "kitty.obj" and
131	write to a Radiance triangle mesh using materials from "kitty.mat":
132	.IP "" .2i
133	robjutil +g cat +g bell kitty.obj \| obj2mesh -a kitty.mat > kitty.rtm
134	.PP
135	To rotate the scene 90 degrees about the Y-axis and scale by 10:
136	.IP "" .2i
137	robjutil -x "-ry 90 -s 10" orig.obj > transformed.obj
138	.SH NOTES
139	The .OBJ output of
140	.I robjutil
141	uses relative indices, so files it produces may be concatenated
142	on the input of other tools such as
143	.I obj2rad
144	and
145	.I obj2mesh
146	by piping from
147	.I cat(1)
148	or similar.
149	This offers a convenient way to separate geometry from a single .OBJ
150	input, manipulate it in some way, then recombine during conversion.
151	.PP
152	Unlike
153	.I obj2rad
154	and
155	.I obj2mesh,
156	.I robjutil
157	with the
158	.I +r
159	option will not substitute the group name for a material id if no
160	.I usemtl
161	statements are found on the input.
162	Instead, it will assign each surface the material
163	.I DEFAULT_MATERIAL.
164	Since it is possible to use the
165	.I +/-g
166	option to select groups to include or exclude on output, it is
167	still possible to assign materials by group manually.
168	.SH AUTHOR
169	Greg Ward
170	.SH "SEE ALSO"
171	cat(1), obj2mesh(1), obj2rad(1) oconv(1), xform(1)