glPolygonOffset(3) glPolygonOffset(3)
NAME
glPolygonOffset - set the scale and units used to calculate depth val-
ues
C SPECIFICATION
void glPolygonOffset( GLfloat factor,
GLfloat units )
PARAMETERS
factor Specifies a scale factor that is used to create a variable
depth offset for each polygon. The initial value is 0.
units Is multiplied by an implementation-specific value to create a
constant depth offset. The initial value is 0.
DESCRIPTION
When GL_POLYGON_OFFSET_FILL, GL_POLYGON_OFFSET_LINE, or
GL_POLYGON_OFFSET_POINT is enabled, each fragment's depth value will be
offset after it is interpolated from the depth values of the appropri-
ate vertices. The value of the offset is factor*DZ + r*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.
glPolygonOffset is useful for rendering hidden-line images, for apply-
ing decals to surfaces, and for rendering solids with highlighted
edges.
NOTES
glPolygonOffset is available only if the GL version is 1.1 or greater.
glPolygonOffset has no effect on depth coordinates placed in the feed-
back buffer.
glPolygonOffset has no effect on selection.
ERRORS
GL_INVALID_OPERATION is generated if glPolygonOffset is executed
between the execution of glBegin and the corresponding execution of
glEnd.
ASSOCIATED GETS
glIsEnabled with argument GL_POLYGON_OFFSET_FILL,
GL_POLYGON_OFFSET_LINE, or GL_POLYGON_OFFSET_POINT.
glGet with argument GL_POLYGON_OFFSET_FACTOR or
GL_POLYGON_OFFSET_UNITS.
SEE ALSO
glDepthFunc(3), glEnable(3), glGet(3), glIsEnabled(3)
glPolygonOffset(3)
Mac OS X 10.6 - Generated Thu Sep 17 20:20:27 CDT 2009