osx man page for glpolygonoffset

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 initial 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 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 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.

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, glEnable, glGet, glIsEnabled

															       GLPOLYGONOFFSET(3G)