82 lines
2.7 KiB
Plaintext
82 lines
2.7 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 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 clipplane
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.ds Xs 34226 5 clipplane.gl
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.TH GLCLIPPLANE 3G
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.SH NAME
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.B "glClipPlane
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\- specify a plane against which all geometry is clipped
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.SH C SPECIFICATION
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void \f3glClipPlane\fP(
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GLenum \fIplane\fP,
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.nf
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.ta \w'\f3void \fPglClipPlane( 'u
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const GLdouble \fI*equation\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'\fIequation\fP\ \ 'u
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\f2plane\fP
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Specifies which clipping plane is being positioned.
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Symbolic names of the form \%\f3GL_CLIP_PLANE\fP\f2i\fP,
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where \f2i\fP is an integer between 0 and \%\f3GL_MAX_CLIP_PLANES\fP$^-^1$,
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are accepted.
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.TP
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\f2equation\fP
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Specifies the address of an array of four double-precision floating-point values.
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These values are interpreted as a plane equation.
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.SH DESCRIPTION
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Geometry is always clipped against the boundaries of a six-plane frustum
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in \f2x\fP, \f2y\fP, and \f2z\fP.
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\%\f3glClipPlane\fP allows the specification of additional planes,
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not necessarily perpendicular to the \f2x\fP, \f2y\fP, or \f2z\fP axis,
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against which all geometry is clipped.
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To determine the maximum number of additional clipping planes, call
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\%\f3glGetIntegerv\fP with argument \%\f3GL_MAX_CLIP_PLANES\fP. All
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implementations support at least six such clipping planes.
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Because the resulting clipping region is the intersection
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of the defined half-spaces,
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it is always convex.
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.P
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\%\f3glClipPlane\fP specifies a half-space using a four-component plane equation.
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When \%\f3glClipPlane\fP is called,
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\f2equation\fP is transformed by the inverse of the modelview matrix
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and stored in the resulting eye coordinates.
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Subsequent changes to the modelview matrix have no effect on the
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stored plane-equation components.
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If the dot product of the eye coordinates of a vertex with the
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stored plane equation components is positive or zero,
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the vertex is \f2in\f1 with respect to that clipping plane.
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Otherwise, it is \f2out\fP.
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.P
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To enable and disable clipping planes, call
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\%\f3glEnable\fP and \%\f3glDisable\fP with the argument
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\%\f3GL_CLIP_PLANE\fP\f2i\fP,
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where \f2i\fP is the plane number.
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.P
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All clipping planes are initially defined as (0, 0, 0, 0) in eye coordinates
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and are disabled.
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.SH NOTES
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It is always the case that \%\f3GL_CLIP_PLANE\fP$i$ = \%\f3GL_CLIP_PLANE0\fP$~+~i$.
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.SH ERRORS
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\%\f3GL_INVALID_ENUM\fP is generated if \f2plane\fP is not an accepted value.
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.P
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\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glClipPlane\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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\%\f3glGetClipPlane\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_CLIP_PLANE\fP\f2i\fP
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.SH SEE ALSO
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\%\f3glEnable(3G)\fP
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