GlPolygonOffset

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


Syntax

 SUB _glPolygonOffset (BYVAL factor AS SINGLE, BYVAL units AS SINGLE)
 void _glPolygonOffset(GLfloat factor, GLfloat 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.


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.


Use With:

_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

SUB _GL _glDepthFunc, _glEnable


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/.



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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/.