Sets the scale and bias used to calculate depth values.
OpenGL C bindings library: libGL.a
void glPolygonOffset(GLfloat factor, GLfloat units)
When GL_POLYGON_OFFSET 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 which is guaranteed to produce a resolveable 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.
This is useful for rendering hidden line images, for applying decals to surfaces, and for rendering solids with highlighted edges.
The glPolygonOffset subroutine is available only if the GL version is 1.1 or greater.
GL_INVALID_OPERATION is generated if glPolygonOffset is executed between the execution of glBegin and the corresponding execution of glEnd.
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.
The glDepthFunc subroutine, glDisable subroutine, glEnable subroutine, glGet subroutine, glIsEnabled subroutine, glLineWidth subroutine, glStencilOp subroutine, glTexEnv subroutine.