GLAPI/glPolygonOffset: Difference between revisions
4.0 API. |
m Math equations. |
||
| Line 17: | Line 17: | ||
== Description == | == Description == | ||
When {{code|GL_POLYGON_OFFSET_FILL}}, {{code|GL_POLYGON_OFFSET_LINE}}, or {{code|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 | When {{code|GL_POLYGON_OFFSET_FILL}}, {{code|GL_POLYGON_OFFSET_LINE}}, or {{code|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. | '''glPolygonOffset''' is useful for rendering hidden-line images, for applying decals to surfaces, and for rendering solids with highlighted edges. | ||
Revision as of 00:35, 30 January 2012
| Core in version | 4.6 | |
|---|---|---|
| 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, glGet, glIsEnabled
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/.