set the scale and units used to calculate depth values
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 , where is a measurement of the change in depth relative to the screen area of the polygon, and 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.
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 .
Copyright 1991-2006 Silicon Graphics, Inc. Copyright 2010-2013 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/ .
Sample Code References
The following code samples have been found which appear to reference the functions described here. Take care that the code may be old, broken or not even use PyOpenGL.
OpenGLContext tests/shadow_1.py Lines: 452