GLPOLYGONOFFSETEXT(3gl)GLPOLYGONOFFSETEXT(3gl)NAME
glPolygonOffsetEXT - set the scale and bias used to calculate depth
values
C SPECIFICATION
void glPolygonOffsetEXT( GLfloat factor,
GLfloat bias )
PARAMETERS
factor Specifies a scale factor multiplied by an implementation-spe‐
cific value to create a variable depth offset for each polygon.
The initial value is 0.
bias Is added to create a constant depth offset. The initial value
is 0.
DESCRIPTION
When GL_POLYGON_OFFSET_EXT is enabled, each fragment's depth value will
be offset after it is interpolated from the depth values of the appro‐
priate vertices. The value of the offset is factor*DZ+bias, where DZ
is a measurement of the change in depth relative to the screen area of
the polygon. The offset is added before the depth test is performed
and before the value is written into the depth buffer.
glPolygonOffsetEXT is useful for rendering hidden-line images, for
applying decals to surfaces, and for rendering solids with highlighted
edges.
NOTES
glPolygonOffsetEXT is part of the GL_EXT_polygon_offset extension. If
GL_EXT_polygon_offset is included in the string returned by glGet‐
String, when called with argument GL_EXTENSIONS, extension GL_EXT_poly‐
gon_offset is supported by the connection.
glPolygonOffsetEXT has no effect on depth coordinates placed in the
feedback buffer.
glPolygonOffsetEXT has no effect on selection.
ERRORS
GL_INVALID_OPERATION is generated if glPolygonOffsetEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
ASSOCIATED GETS
glIsEnabled with argument GL_POLYGON_OFFSET_EXT.
glGet with argument GL_POLYGON_OFFSET_FACTOR_EXT or GL_POLYGON_OFF‐
SET_BIAS_EXT.
SEE ALSO
glDepthFunc, glDisable, glEnable, glGet, glIsEnabled, glLineWidth, glS‐
tencilOp, glTexEnv
13 May 98 GLPOLYGONOFFSETEXT(3gl)