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38 lines
1.8 KiB
Text
38 lines
1.8 KiB
Text
'''_glPolygonOffset:''' set the scale and units used to calculate depth values
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{{PageSyntax}}
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SUB _glPolygonOffset (BYVAL factor AS SINGLE, BYVAL units AS SINGLE)
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void '''_glPolygonOffset'''(GLfloat {{Parameter|factor}}, GLfloat {{Parameter|units}});
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; factor
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: Specifies a scale factor that is used to create a variable depth offset for each polygon. The initial value is 0.
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; units
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: Is multiplied by an implementation-specific value to create a constant depth offset. The initial value is 0.
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{{PageDescription}}
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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.
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'''_glPolygonOffset''' is useful for rendering hidden-line images, for applying decals to surfaces, and for rendering solids with highlighted edges.
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{{PageUseWith}}
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{{KW|_glIsEnabled}} with argument {{KW|_GL_POLYGON_OFFSET_FILL}}, {{KW|_GL_POLYGON_OFFSET_LINE}}, or {{KW|_GL_POLYGON_OFFSET_POINT}}.
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{{KW|_glGet}} with argument {{KW|_GL_POLYGON_OFFSET_FACTOR}} or {{KW|_GL_POLYGON_OFFSET_UNITS}}.
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{{PageSeeAlso}}
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[[_GL|SUB _GL]]
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{{KW|_glDepthFunc}}, {{KW|_glEnable}}
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{{PageCopyright}}
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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/ http://oss.sgi.com/projects/FreeB/].
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