man/man1/robjutil.1

.\" RCSid "$Id: robjutil.1,v 1.7 2021/04/15 23:51:04 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 +T
][
.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 more useful for preserving
texture coordinates if directed to
.I obj2mesh(1).
.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).
To break all surfaces into triangles, include the
.I +T
option.
.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 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), genbox(1), gensurf(1), obj2mesh(1), obj2rad(1) oconv(1), xform(1)
Revision:	1.8
Committed:	Tue Jan 31 16:29:19 2023 UTC (2 years, 9 months ago) by greg
Branch:	MAIN
CVS Tags:	rad6R0, rad5R4, HEAD
Changes since 1.7:	+3 -4 lines
Log Message:	docs(robjutil): improved clarity on +T option
#	Content
1	.\" RCSid "$Id: robjutil.1,v 1.7 2021/04/15 23:51:04 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 +T
23	][
24	.B "-x 'xf spec'"
25	]
26	[
27	.B input.obj ..
28	]
29	.SH DESCRIPTION
30	.I Robjutil
31	reads and manipulates a Wavefront .OBJ file, removing degenerate and
32	duplicate faces.
33	If the
34	.I +r
35	option is specified, a Radiance scene description
36	will be produced on the standard output.
37	If
38	.I -r
39	is given, a modified .OBJ file will be sent to the standard output.
40	This is the default, and is more useful for preserving
41	texture coordinates if directed to
42	.I obj2mesh(1).
43	.PP
44	The
45	.I +v
46	option turns on verbose progress reports.
47	.PP
48	The
49	.I \-t
50	option tells
51	.I robjutil
52	to remove texture coordinates from the input.
53	The
54	.I \-n
55	option will cause all surface normals to be removed.
56	.PP
57	The
58	.I "\-m mname"
59	option tells
60	.I robjutil
61	to remove all faces that use the material
62	.I mname.
63	Multiple
64	.I \-m
65	options may be given, each with a single (unique) material name.
66	Alternatively, the
67	.I "+m mname"
68	option may be used to specify a material one wishes to keep, discarding the rest.
69	Multiple
70	.I +m
71	options will keep all the named materials.
72	The
73	.I \-m
74	and
75	.I \+m
76	options are mutually exclusive.
77	.PP
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	Object statements are treated the same as group statements in the input, so
89	.I +/-g
90	option can also be applied to object names.
91	Note that an object name will be overridden by a group name that follows
92	it in the input, and vice versa.
93	.PP
94	The
95	.I "\-c epsilon"
96	option tells
97	.I robjutil
98	to coalesce vertices that are within the given epsilon.
99	This is useful to improve the connectivity of models that were produced
100	in a sloppy conversion process from independent polygons.
101	When producing a Radiance file via the
102	.I +r
103	option, there will be no savings in the output size, but there can be
104	a benefit in reducing the number of "cracks" in the resulting geometry,
105	at least for triangle mesh input.
106	.I Robjutil
107	does not attempt to break up non-planar polygons into triangles,
108	which is usually not a problem for .OBJ output, but may be for Radiance
109	scene descriptions (+r).
110	To break all surfaces into triangles, include the
111	.I +T
112	option.
113	.PP
114	The
115	.I \-x
116	option may be used to specify a final transform to apply to all
117	coordinates in the file before output.
118	This specification must be contained in a single quoted word and
119	match the standard arguments used by
120	.I xform(1),
121	except that the
122	.I \-a
123	option is not supported for creating arrays of objects.
124	Also, any scaling factors do not affect the epsilon value given for
125	coalescing vertices, as this operation is applied prior to the transform,
126	even if
127	.I \-c
128	appears later in the command line.
129	.SH EXAMPLES
130	To remove degenerate and duplicate faces from "orig.obj" and write to "final.rad":
131	.IP "" .2i
132	robjutil +r orig.obj > final.rad
133	.PP
134	To extract only the groups "cat" and "bell" from the file "kitty.obj" and
135	write to a Radiance triangle mesh using materials from "kitty.mat":
136	.IP "" .2i
137	robjutil +g cat +g bell kitty.obj \| obj2mesh -a kitty.mat > kitty.rtm
138	.PP
139	To rotate the scene 90 degrees about the Y-axis and scale by 10:
140	.IP "" .2i
141	robjutil -x "-ry 90 -s 10" orig.obj > transformed.obj
142	.SH NOTES
143	The .OBJ output of
144	.I robjutil
145	uses relative indices, so files it produces may be concatenated
146	on the input of other tools such as
147	.I obj2rad
148	and
149	.I obj2mesh
150	by piping from
151	.I cat(1)
152	or similar.
153	This offers a convenient way to separate geometry from a single .OBJ
154	input, manipulate it in some way, then recombine during conversion.
155	.PP
156	Unlike
157	.I obj2rad
158	and
159	.I obj2mesh,
160	.I robjutil
161	with the
162	.I +r
163	option will not substitute the group name for a material id if no
164	.I usemtl
165	statements are found on the input.
166	Instead, it will assign each surface the material
167	.I DEFAULT_MATERIAL.
168	Since it is possible to use the
169	.I +/-g
170	option to select groups to include or exclude on output, it is
171	still possible to assign materials by group manually.
172	.SH AUTHOR
173	Greg Ward
174	.SH "SEE ALSO"
175	cat(1), genbox(1), gensurf(1), obj2mesh(1), obj2rad(1) oconv(1), xform(1)