'''_glPolygonOffset:''' set the scale and units used to calculate depth values


{{PageSyntax}}

  SUB _glPolygonOffset (BYVAL factor AS SINGLE, BYVAL units AS SINGLE)
  void '''_glPolygonOffset'''(GLfloat {{Parameter|factor}}, GLfloat {{Parameter|units}});


; 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.


{{PageDescription}}

When {{KW|_GL_POLYGON_OFFSET_FILL}}, {{KW|_GL_POLYGON_OFFSET_LINE}}, or {{KW|_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.


{{PageUseWith}}

{{KW|_glIsEnabled}} with argument {{KW|_GL_POLYGON_OFFSET_FILL}}, {{KW|_GL_POLYGON_OFFSET_LINE}}, or {{KW|_GL_POLYGON_OFFSET_POINT}}.

{{KW|_glGet}} with argument {{KW|_GL_POLYGON_OFFSET_FACTOR}} or {{KW|_GL_POLYGON_OFFSET_UNITS}}.


{{PageSeeAlso}}

{{KW|_GL}}
{{KW|_glDepthFunc}}, {{KW|_glEnable}}


{{PageCopyright}}

Copyright 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see [http://oss.sgi.com/projects/FreeB/ http://oss.sgi.com/projects/FreeB/].