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.\" RCSid "$Id: xform.1,v 1.5 2015/06/29 00:32:51 greg Exp $"
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.TH XFORM 1 6/4/99 RADIANCE
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.SH NAME
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xform - transform a RADIANCE scene description
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.SH SYNOPSIS
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.B xform
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[
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.B \-c
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][
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.B \-I
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][
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.B "\-n name"
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][
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.B "\-m newmod"
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][
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.B "\-f argfile"
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][
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.B xf0
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][
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.B "\-a n1 xf1 .."
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][
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.B "\-i 1 xff"
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]
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.B "file .."
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.SH DESCRIPTION
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.I Xform
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transforms each scene description
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.I file
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according to the options given.
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If no
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.I file
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is specified, the standard input is read.
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The
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.I \-c
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option causes commands in the input not to be expanded.
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The default is to execute all in line commands.
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(See note below about file names.)\0
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The
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.I \-n
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option causes all identifiers to be prefixed with
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.I name.
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The
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.I \-m
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option causes all surfaces to be given the modifier
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.I newmod.
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The
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.I \-I
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option causes all surfaces to be inverted, reversing their
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surface normal orientations.
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These options are followed by the transformation options,
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which are described below.
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.PP
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The
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.I \-f
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option causes the
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.I xform
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command line to be constructed from the given file,
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by inserting each line of the file at the
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current point in the command argument list.
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Each line in the file will result in a logically separate invocation of
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.I xform,
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and may contain any valid
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.I xform
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arguments, including nested
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.I \-f
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options.
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This is a convenient way to specify multiple copies of an object that
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do not fit a regular array pattern, without having to actually execute
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.I xform
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many times.
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Separate scene files may be specified this way as well, but remember
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that the constructed command line must fit the format of initial options
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.I "(-n, -m, -c, -I)"
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followed by the transform then the scene files.
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No initial options may appear after the first transform option, and
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no transform options will be understood after the first named file.
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In the special case where the argument to the
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.I \-f
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option is a hyphen ('-'),
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.I xform
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will take its arguments from the standard input.
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Note that
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.I xform
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cannot simultaneously take its scene information from the standard input
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if the option is used in this way.
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Competely empty lines and lines beginning with a pound sign ('#') will be
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passed through to the output.
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Beginning "!xform" or "xform" command names will also be ignored.
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.PP
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If one or more scene files are given on the command line,
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.I xform
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will search the RADIANCE library directories for each file.
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(No search takes place if a file name begins with a '.', '/' or '~'
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character.)\0
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Unless the
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.I \-c
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option is present,
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.I xform
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will also change to that file's directory before loading it.
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Thus, any commands executed within that file will happen in that
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file's directory, which simplifies object hierarchy construction.
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.PP
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The transformation consists of a sequence of operations which
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are executed in the order they appear.
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.SH OPTIONS
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.TP 10n
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.BI -t " x y z"
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Translate the scene along the vector
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.I "x y z".
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.TP
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.BI -rx \ degrees
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Rotate the scene
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.I degrees
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about the x axis.
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A positive rotation corresponds to counter-clockwise
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when looking down the axis.
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.TP
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.BI -ry \ degrees
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Rotate the scene
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.I degrees
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about the y axis.
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.TP
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.BI -rz \ degrees
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Rotate the scene
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.I degrees
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about the z axis.
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.TP
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.BI -s \ factor
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Scale the scene by
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.I factor.
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.TP
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.BR \-mx
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Mirror the scene about the yz plane.
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.TP
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.BR \-my
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Mirror the scene about the xz plane.
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.TP
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.BR \-mz
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Mirror the scene about the xy plane.
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.TP
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.BI -i \ count
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Iterate (repeat) the following transformation (up to the next
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.I \-i
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option)
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.I count
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times.
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This option is primarily to support the
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.I \-a
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option, which is described below.
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.SS Arrays
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An array is a repeated transformation that results in a repeated object.
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It is specified using the
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.I \-a
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option, which takes the number to repeat as its argument.
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The objects will step by the transformation given between
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this
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.I \-a
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option and the next
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.I \-a
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or
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.I \-i
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option.
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The first object will have zero applications of the transform.
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A two-dimensional array is given by two different transformations
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each preceded by an array count.
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.SH EXAMPLE
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To rotate ``book'' 30 degrees about the x axis then
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move 20 in y, prepending the name book1:
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.IP "" .2i
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xform \-n book1 \-rx 30 \-t 0 20 0 book > book1
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.PP
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To expand all commands and see what information is actually used by RADIANCE:
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.IP "" .2i
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xform scene | more
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.PP
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To create a two-dimensional array of 20 lights, after an initial rotation
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and followed by a global translation (no command expansion):
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.IP "" .2i
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xform \-c \-rz 90 \-a 5 \-t 2 0 0 \-a 4 \-t 0 1.5 0 \-i 1 \-t 0 0 10 light
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.SH ENVIRONMENT
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RAYPATH path to search for scene files
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.SH AUTHOR
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Greg Ward
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.SH BUGS
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Only regular (distortion-free) transformations are allowed.
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.SH "SEE ALSO"
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genbox(1), gensurf(1), oconv(1), replmarks(1), rpict(1), rvu(1)
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