glPolygonOffset(3G)glPolygonOffset(3G)NAMEglPolygonOffset - set the scale and units used to calculate depth val‐
ues
SYNOPSIS
void glPolygonOffset(
GLfloat factor,
GLfloat units );
PARAMETERS
Specifies a scale factor that is used to create a variable depth offset
for each polygon. The initial value is 0. Is multiplied by an imple‐
mentation-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_OFF‐
SET_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 mea‐
surement 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.
NOTESglPolygonOffset() 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 GETSglIsEnabled() with argument GL_POLYGON_OFFSET_FILL, GL_POLYGON_OFF‐
SET_LINE, or GL_POLYGON_OFFSET_POINT.
glGet() with argument GL_POLYGON_OFFSET_FACTOR or GL_POLYGON_OFF‐
SET_UNITS.
SEE ALSOglDepthFunc(3), glEnable(3), glGet(3), glIsEnabled(3)glPolygonOffset(3G)