GLAPI/glPolygonOffset

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glPolygonOffset
Core in version 4.4
Core since version 1.0

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

Function Definition

 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.

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

Copyright

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/.