73 lines
1.8 KiB
Plaintext
73 lines
1.8 KiB
Plaintext
'\" 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 viewport.
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.ds Xs 35742 4 viewport.gl
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.TH GLVIEWPORT 3G
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.SH NAME
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.B "glViewport
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\- set the viewport
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.SH C SPECIFICATION
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void \f3glViewport\fP(
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GLint \fIx\fP,
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.nf
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.ta \w'\f3void \fPglViewport( 'u
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GLint \fIy\fP,
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GLsizei \fIwidth\fP,
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GLsizei \fIheight\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'\f2x\fP\ \f2y\fP\ \ 'u
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\f2x\fP, \f2y\fP
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Specify the lower left corner of the viewport rectangle,
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in pixels. The initial value is (0,0).
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.TP
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\f2width\fP, \f2height\fP
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Specify the width and height
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of the viewport.
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When a GL context is first attached to a window,
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\f2width\fP and \f2height\fP are set to the dimensions of that window.
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.SH DESCRIPTION
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\%\f3glViewport\fP specifies the affine transformation of $x$ and $y$ from
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normalized device coordinates to window coordinates.
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Let ($x sub nd$, $y sub nd$) be normalized device coordinates.
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Then the window coordinates ($x sub w$, $y sub w$) are computed as follows:
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.sp
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.ce
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.EQ
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x sub w ~=~ ( x sub nd ~+~ 1 ) left ( "width" over 2 right ) ~+~ "x"
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.EN
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.sp
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.ce
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.EQ
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y sub w ~=~ ( y sub nd ~+~ 1 ) left ( "height" over 2 right ) ~+~ "y"
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.EN
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.RE
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.P
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Viewport width and height are silently clamped
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to a range that depends on the implementation.
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To query this range, call \%\f3glGet\fP with argument
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\%\f3GL_MAX_VIEWPORT_DIMS\fP.
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.SH ERRORS
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\%\f3GL_INVALID_VALUE\fP is generated if either \f2width\fP or \f2height\fP is negative.
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.P
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\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glViewport\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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.bp
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.SH ASSOCIATED GETS
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\%\f3glGet\fP with argument \%\f3GL_VIEWPORT\fP
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.br
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\%\f3glGet\fP with argument \%\f3GL_MAX_VIEWPORT_DIMS\fP
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.SH SEE ALSO
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\%\f3glDepthRange(3G)\fP
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