.TH gSPPerspNormalize 3P local "Silicon Graphics, Inc."
.SH NAME
.upperok
gSPPerspNormalize, gsSPPerspNormalize
\- perspective normalization
.SH C SPECIFICATION
.nf
\f3#include "gbi.h"

gSPPerspNormalize(Gfx *gdl, u16 scale)

gsSPPerspNormalize(u16 scale)

\fP
.fi
.SH PARAMETERS
.TP 10
.I *gdl
graphics display list pointer.
.TP
.I scale
the perspective normalization scale, in .16 format.
.SH DESCRIPTION
This scale value is used to scale the transformed w coordinate down, prior
to dividing out w to compute the screen coordinates (which are similarly
scaled). The effect of this is to maximize the precision of this divide
(which is computed with a limited precision in the RSP geometry engine).
.SH NOTE
The library function 
.IR guPerspective (3P) 
returns one approximation for this scale
value, which is suitable for most cases. This estimate normalizes w so that
w = 1.0 halfway between the near and far clipping planes.