DragonFly On-Line Manual Pages

GLPOLYGONOFFSET()                                            GLPOLYGONOFFSET()

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 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, glDisable, glEnable, glGet, glIsEnabled, glLineWidth,
       glStencilOp, glTexEnv

                                                             GLPOLYGONOFFSET()