'\" t
.\"     Title: glPolygonOffset
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.76.1 <http://docbook.sf.net/>
.\"      Date: 03/08/2011
.\"    Manual: OpenGL 3.3
.\"    Source: OpenGL 3.3
.\"  Language: English
.\"
.TH "GLPOLYGONOFFSET" "3G" "03/08/2011" "OpenGL 3.3" "OpenGL 3\&.3"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
glPolygonOffset \- set the scale and units used to calculate depth values
.SH "C SPECIFICATION"
.HP \w'void\ glPolygonOffset('u
.BI "void glPolygonOffset(GLfloat\ " "factor" ", GLfloat\ " "units" ");"
.SH "PARAMETERS"
.PP
\fIfactor\fR
.RS 4
Specifies a scale factor that is used to create a variable depth offset for each polygon\&. The initial value is 0\&.
.RE
.PP
\fIunits\fR
.RS 4
Is multiplied by an implementation\-specific value to create a constant depth offset\&. The initial value is 0\&.
.RE
.SH "DESCRIPTION"
.PP
When
\fBGL_POLYGON_OFFSET_FILL\fR,
\fBGL_POLYGON_OFFSET_LINE\fR, or
\fBGL_POLYGON_OFFSET_POINT\fR
is enabled, each fragment\*(Aqs
\fIdepth\fR
value will be offset after it is interpolated from the
\fIdepth\fR
values of the appropriate vertices\&. The value of the offset is
factor \(mu DZ + r \(mu units, where
DZ
is a measurement of the change in depth relative to the screen area of the polygon, and
r
is the smallest value that is guaranteed to produce a resolvable offset for a given implementation\&. The offset is added before the depth test is performed and before the value is written into the depth buffer\&.
.PP

\fBglPolygonOffset\fR
is useful for rendering hidden\-line images, for applying decals to surfaces, and for rendering solids with highlighted edges\&.
.SH "ASSOCIATED GETS"
.PP

\fBglIsEnabled\fR()
with argument
\fBGL_POLYGON_OFFSET_FILL\fR,
\fBGL_POLYGON_OFFSET_LINE\fR, or
\fBGL_POLYGON_OFFSET_POINT\fR\&.
.PP

\fBglGet\fR()
with argument
\fBGL_POLYGON_OFFSET_FACTOR\fR
or
\fBGL_POLYGON_OFFSET_UNITS\fR\&.
.SH "SEE ALSO"
.PP

\fBglDepthFunc\fR(),
\fBglEnable\fR(),
\fBglGet\fR(),
\fBglIsEnabled\fR()
.SH "COPYRIGHT"
.PP
Copyright
\(co
1991\-2006 Silicon Graphics, Inc\&. This document is licensed under the SGI Free Software B License\&. For details, see
\m[blue]\fBhttp://oss\&.sgi\&.com/projects/FreeB/\fR\m[]\&.