68 lines
2.0 KiB
Plaintext
68 lines
2.0 KiB
Plaintext
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'\" 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 6 March 1997
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.ds Re Release 1.2.0
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.ds Dp May 02 11:53
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.ds Dm 37 tessnorma
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.ds Xs 47097 4 tessnormal.gl
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.TH GLUTESSNORMAL 3G
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.SH NAME
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.B "gluTessNormal
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\- specify a normal for a polygon
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.SH C SPECIFICATION
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void \f3gluTessNormal\fP(
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GLUtesselator* \fItess\fP,
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.nf
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.ta \w'\f3void \fPgluTessNormal( 'u
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GLdouble \fIvalueX\fP,
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GLdouble \fIvalueY\fP,
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GLdouble \fIvalueZ\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'\fIvalueX\fP\ \ 'u
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\f2tess\fP
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Specifies the tessellation object (created with \%\f3gluNewTess\fP).
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.TP
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\f2valueX\fP
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Specifies the first component of the normal.
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.TP
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\f2valueY\fP
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Specifies the second component of the normal.
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.TP
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\f2valueZ\fP
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Specifies the third component of the normal.
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.SH DESCRIPTION
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\%\f3gluTessNormal\fP describes a normal for a polygon that the program is defining.
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All input data will be projected onto a plane perpendicular to one of
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the three coordinate axes before tessellation and all output triangles
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will be oriented CCW with
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respect to the normal (CW orientation can be obtained by reversing the
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sign of the supplied normal). For example, if you know that all polygons
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lie in the x-y plane, call \%\f3gluTessNormal\fP(tess, 0.0, 0.0, 1.0)
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before rendering any polygons.
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.P
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If the supplied normal is (0.0, 0.0, 0.0) (the initial value), the normal is
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determined as follows. The direction of the normal, up to its sign, is
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found by fitting a plane to the vertices, without regard to how the
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vertices are connected. It is expected that the input data lies approximately
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in the plane; otherwise, projection perpendicular to one of the three
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coordinate axes may substantially change the geometry. The sign of the
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normal is chosen so that the sum of the signed areas of all input
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contours is nonnegative (where a CCW contour has positive area).
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.P
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The supplied normal persists until it is changed by another call to
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\%\f3gluTessNormal\fP.
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.SH SEE ALSO
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\%\f3gluTessBeginPolygon(3G)\fP,
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\%\f3gluTessEndPolygon(3G)\fP
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