man/man1/robjutil.1

.\" RCSid "$Id: robjutil.1,v 1.4 2020/04/03 02:32:58 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.
.PP
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.
.PP
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).
Object statements are treated the same as group statements in the input, so
.I +/-g
option can also be applied to object names.
Note that an object name will be overridden by a group name that follows
it in the input, and vice versa.
.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:	1.5
Committed:	Fri Apr 3 02:45:13 2020 UTC (5 years, 1 month ago) by greg
Branch:	MAIN
CVS Tags:	rad5R3
Changes since 1.4:	+8 -1 lines
Log Message:	Added some notes about object and group statements being treated the same
#	Content
1	.\" RCSid "$Id: robjutil.1,v 1.4 2020/04/03 02:32:58 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	.PP
46	The
47	.I +v
48	option turns on verbose progress reports.
49	.PP
50	The
51	.I \-t
52	option tells
53	.I robjutil
54	to remove texture coordinates from the input.
55	The
56	.I \-n
57	option will cause all surface normals to be removed.
58	.PP
59	The
60	.I "\-m mname"
61	option tells
62	.I robjutil
63	to remove all faces that use the material
64	.I mname.
65	Multiple
66	.I \-m
67	options may be given, each with a single (unique) material name.
68	Alternatively, the
69	.I "+m mname"
70	option may be used to specify a material one wishes to keep, discarding the rest.
71	Multiple
72	.I +m
73	options will keep all the named materials.
74	The
75	.I \-m
76	and
77	.I \+m
78	options are mutually exclusive.
79	.PP
80	Similarly, the
81	.I "\-g gname"
82	option says to remove all faces belonging to the group
83	.I gname,
84	and multiple
85	.I \-g
86	options may be given.
87	There is also a
88	.I +g
89	option to save just the named group(s).
90	Object statements are treated the same as group statements in the input, so
91	.I +/-g
92	option can also be applied to object names.
93	Note that an object name will be overridden by a group name that follows
94	it in the input, and vice versa.
95	.PP
96	The
97	.I "\-c epsilon"
98	option tells
99	.I robjutil
100	to coalesce vertices that are within the given epsilon.
101	This is useful to improve the connectivity of models that were produced
102	in a sloppy conversion process from independent polygons.
103	When producing a Radiance file via the
104	.I +r
105	option, there will be no savings in the output size, but there can be
106	a benefit in reducing the number of "cracks" in the resulting geometry,
107	at least for triangle mesh input.
108	.I Robjutil
109	does not attempt to break up non-planar polygons into triangles,
110	which is usually not a problem for .OBJ output, but may be for Radiance
111	scene descriptions (+r).
112	.PP
113	The
114	.I \-x
115	option may be used to specify a final transform to apply to all
116	coordinates in the file before output.
117	This specification must be contained in a single quoted word and
118	match the standard arguments used by
119	.I xform(1),
120	except that the
121	.I \-a
122	option is not supported for creating arrays of objects.
123	Also, any scaling factors do not affect the epsilon value given for
124	coalescing vertices, as this operation is applied prior to the transform,
125	even if
126	.I \-c
127	appears later in the command line.
128	.SH EXAMPLES
129	To remove degenerate and duplicate faces from "orig.obj" and write to "final.rad":
130	.IP "" .2i
131	robjutil +r orig.obj > final.rad
132	.PP
133	To convert the same file, preserving surface normal interpolation:
134	.IP "" .2i
135	robjutil orig.obj \| obj2rad > withnormals.rad
136	.PP
137	To extract only the groups "cat" and "bell" from the file "kitty.obj" and
138	write to a Radiance triangle mesh using materials from "kitty.mat":
139	.IP "" .2i
140	robjutil +g cat +g bell kitty.obj \| obj2mesh -a kitty.mat > kitty.rtm
141	.PP
142	To rotate the scene 90 degrees about the Y-axis and scale by 10:
143	.IP "" .2i
144	robjutil -x "-ry 90 -s 10" orig.obj > transformed.obj
145	.SH NOTES
146	The .OBJ output of
147	.I robjutil
148	uses relative indices, so files it produces may be concatenated
149	on the input of other tools such as
150	.I obj2rad
151	and
152	.I obj2mesh
153	by piping from
154	.I cat(1)
155	or similar.
156	This offers a convenient way to separate geometry from a single .OBJ
157	input, manipulate it in some way, then recombine during conversion.
158	.PP
159	Unlike
160	.I obj2rad
161	and
162	.I obj2mesh,
163	.I robjutil
164	with the
165	.I +r
166	option will not substitute the group name for a material id if no
167	.I usemtl
168	statements are found on the input.
169	Instead, it will assign each surface the material
170	.I DEFAULT_MATERIAL.
171	Since it is possible to use the
172	.I +/-g
173	option to select groups to include or exclude on output, it is
174	still possible to assign materials by group manually.
175	.SH AUTHOR
176	Greg Ward
177	.SH "SEE ALSO"
178	cat(1), obj2mesh(1), obj2rad(1) oconv(1), xform(1)