73 lines
2.3 KiB
Text
73 lines
2.3 KiB
Text
'\" e
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'\"! eqn | mmdoc
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'\"macro stdmacro
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.ds Vn Version 1.2
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.ds Dt 24 September 1999
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.ds Re Release 1.2.1
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.ds Dp Jan 14 18:30
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.ds Dm 01 polygonof
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.ds Xs 10762 4 polygonoffset.gl
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.TH GLPOLYGONOFFSET 3G
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.SH NAME
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.B "glPolygonOffset
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\- set the scale and units used to calculate depth values
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.SH C SPECIFICATION
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void \f3glPolygonOffset\fP(
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GLfloat \fIfactor\fP,
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.nf
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.ta \w'\f3void \fPglPolygonOffset( 'u
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GLfloat \fIunits\fP )
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.fi
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.EQ
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delim $$
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.EN
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.SH PARAMETERS
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.TP \w'\f2factor\fP\ \ 'u
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\f2factor\fP
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Specifies a scale factor that is used to create a variable
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depth offset for each polygon. The initial value is 0.
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.TP
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\f2units\fP
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Is multiplied by an implementation-specific value to
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create a constant depth offset. The initial value is 0.
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.SH DESCRIPTION
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When \%\f3GL_POLYGON_OFFSET_FILL\fP, \%\f3GL_POLYGON_OFFSET_LINE\fP, or
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\%\f3GL_POLYGON_OFFSET_POINT\fP is enabled, each
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fragment's \f2depth\fP value will be offset after it is interpolated
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from the \f2depth\fP values of the appropriate vertices.
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The value of the offset is $"factor" ~*~ DZ ~~+~~ r ~*~ "units"$,
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where $DZ~$ is a measurement of the change in depth relative to the screen
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area of the polygon, and $r$ is the smallest value that is guaranteed to
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produce a resolvable offset for a given implementation.
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The offset is added before the depth test is performed and before
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the value is written into the depth buffer.
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.P
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\%\f3glPolygonOffset\fP is useful for rendering hidden-line images, for applying decals
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to surfaces, and for rendering solids with highlighted edges.
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.SH NOTES
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\%\f3glPolygonOffset\fP is available only if the GL version is 1.1 or greater.
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.P
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\%\f3glPolygonOffset\fP has no effect on depth coordinates placed in the
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feedback buffer.
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.P
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\%\f3glPolygonOffset\fP has no effect on selection.
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.SH ERRORS
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\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glPolygonOffset\fP is executed
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between the execution of \%\f3glBegin\fP and the corresponding
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execution of \%\f3glEnd\fP.
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.bp
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.SH ASSOCIATED GETS
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\%\f3glIsEnabled\fP with argument
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\%\f3GL_POLYGON_OFFSET_FILL\fP,
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\%\f3GL_POLYGON_OFFSET_LINE\fP,
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or \%\f3GL_POLYGON_OFFSET_POINT\fP.
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.P
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\%\f3glGet\fP with argument \%\f3GL_POLYGON_OFFSET_FACTOR\fP or
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\%\f3GL_POLYGON_OFFSET_UNITS\fP.
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.SH SEE ALSO
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\%\f3glDepthFunc(3G)\fP,
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\%\f3glEnable(3G)\fP,
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\%\f3glGet(3G)\fP,
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\%\f3glIsEnabled(3G)\fP
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