.TH modify  3 "R1c" "Silicon Graphics"
.SH NAME
.I modify
- define a linear mapping between a valuator and a command argument
.SH SYNOPSIS
.nf
.TP "w`FORTRAN   `u"
C
.B "modify(obj, tagname, offst, argnum, a, b, v) "
.B "Object obj; "
.B "Tag tagname; "
.B "Offset offst; "
.B "short argnum; "
.B "float a, b;"
.B "Device v;"
.IP 
.TP "w`FORTRAN   `u"
FORTRAN
.B "subroutine modify(obj, tagnam, offst, argnum, a, b, v)"
.B "integer obj, tagnam, offst"
.B "integer*2 argnum, v"
.B "real a, b"
.IP 
.TP "w`FORTRAN   `u"
Pascal
.B "procedure modify(obj: Object; tagname: Tag; offst: Offset; "
.B "	argnum: Short; a, b: real; v: Device);"
.sp
.SH DESCRIPTION
The \f2modify\f1 command provides a general mechanism for defining a linear
mapping between an input device and a command argument.  The 
first four parameters, \f3obj\f1, \f3tagname\f1, 
\f3offst\f1, and \f3argnum\f1, uniquely 
define an argument to a command in a display list.  The next two, \f3a\f1 and
\f3b\f1, are coefficients used in the computation of the new value for the
selected argument, and \f3v\f1 selects a valuator device.  The mapping is
\f3a\f1 $times$ \f2getvaluator(v)\f1 + \f3b\f1.
.PP
The 
.I modify
is implemented for the following commands:
.TS
center ;
lI lI lI lI 
lI lI lI lI 
lI lI lI lI 
lI lI lI lI 
lI lI lI lI.
cmov	cmovi	cmov2	cmov2i
draw	drawi	draw2	draw2i
move	movei	move2	move2i
pnt	pnti	pnt2	pnt2i
rect	recti	rectf	rectfi
.TE
.TS
center ;
lI lI lI.
lookat	perspective	scale
ortho	polarview	translate
ortho2	rotate	window
.TE
.SH "SEE ALSO"
.I getvaluator