GLPOLYGONOFFSET(3G) 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 ini-tial initial
tial 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 appropriate
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 guar-anteed guaranteed
anteed 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.
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(3G), glEnable(3G), glGet(3G), glIsEnabled(3G)
GLPOLYGONOFFSET(3G)
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