glPolygonOffset(3G) OpenGL Reference glPolygonOffset(3G)NAME
glPolygonOffset - set the scale and units used to calculate depth values
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 appropriate
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 applying
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 feedback
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.
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glPolygonOffset(3G) OpenGL Reference glPolygonOffset(3G)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.
MACHINE DEPENDENCIES
GL_POLYGON_OFFSET_LINE and GL_POLYGON_OFFSET_POINT are not implemented on
XS, XZ, Elan, and Extreme, RealityEngine, RealityEngine2, and VTX and
InfiniteReality systems.
SEE ALSO
glDepthFunc, glDisable, glEnable, glGet, glIsEnabled, glLineWidth,
glStencilOp, glTexEnv
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