88 lines
2.5 KiB
Plaintext
88 lines
2.5 KiB
Plaintext
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'\" te
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'\"! tbl|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 shademode
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.ds Xs 4246 5 shademodel.gl
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.TH GLSHADEMODEL 3G
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.SH NAME
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.B "glShadeModel
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\- select flat or smooth shading
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.SH C SPECIFICATION
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void \f3glShadeModel\fP(
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GLenum \fImode\fP )
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.nf
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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'\f2mode\fP\ \ 'u
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\f2mode\fP
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Specifies a symbolic value representing a shading technique.
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Accepted values are \%\f3GL_FLAT\fP and \%\f3GL_SMOOTH\fP.
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The initial value is \%\f3GL_SMOOTH\fP.
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.SH DESCRIPTION
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GL primitives can have either flat or smooth shading.
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Smooth shading,
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the default,
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causes the computed colors of vertices to be interpolated as the
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primitive is rasterized,
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typically assigning different colors to each resulting pixel fragment.
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Flat shading selects the computed color of just one vertex
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and assigns it to all the pixel fragments
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generated by rasterizing a single primitive.
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In either case, the computed color of a vertex is the result of
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lighting if lighting is enabled,
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or it is the current color at the time the vertex was specified if
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lighting is disabled.
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.P
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Flat and smooth shading are indistinguishable for points.
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Starting when \%\f3glBegin\fP is issued and counting vertices and
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primitives from 1, the GL gives each flat-shaded line segment $i$ the
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computed color of vertex $i ~+~ 1$, its second vertex.
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Counting similarly from 1,
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the GL gives each flat-shaded polygon the computed color of the vertex listed
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in the following table.
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This is the last vertex to specify the polygon in all cases except single
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polygons,
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where the first vertex specifies the flat-shaded color.
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.sp
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.TS
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center;
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lb cb
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l c .
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_
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Primitive Type of Polygon $i$ Vertex
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_
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Single polygon ($ i ~==~ 1 $) 1
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Triangle strip $i ~+~ 2$
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Triangle fan $i ~+~ 2$
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Independent triangle $ 3 i$
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Quad strip $2 i ~+~ 2$
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Independent quad $ 4 i $
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_
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.TE
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.sp
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Flat and smooth shading are specified by \%\f3glShadeModel\fP with \f2mode\fP set to
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\%\f3GL_FLAT\fP and \%\f3GL_SMOOTH\fP, respectively.
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.SH ERRORS
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\%\f3GL_INVALID_ENUM\fP is generated if \f2mode\fP is any value other than
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\%\f3GL_FLAT\fP or \%\f3GL_SMOOTH\fP.
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.P
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\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glShadeModel\fP
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is executed between the execution of \%\f3glBegin\fP
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and the corresponding execution of \%\f3glEnd\fP.
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.SH ASSOCIATED GETS
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\%\f3glGet\fP with argument \%\f3GL_SHADE_MODEL\fP
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.SH SEE ALSO
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\%\f3glBegin(3G)\fP,
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\%\f3glColor(3G)\fP,
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\%\f3glLight(3G)\fP,
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\%\f3glLightModel(3G)\fP
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