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+'\" e
+'\"! eqn | mmdoc
+'\"macro stdmacro
+.ds Vn Version 1.2
+.ds Dt 6 March 1997
+.ds Re Release 1.2.0
+.ds Dp May 02 11:53
+.ds Dm 37 unproject
+.ds Xs 63442 4 unproject.gl
+.TH GLUUNPROJECT 3G
+.SH NAME
+.B "gluUnProject
+\- map window coordinates to object coordinates
+
+.SH C SPECIFICATION
+GLint \f3gluUnProject\fP(
+GLdouble \fIwinX\fP,
+.nf
+.ta \w'\f3GLint \fPgluUnProject( 'u
+	GLdouble \fIwinY\fP,
+	GLdouble \fIwinZ\fP,
+	const GLdouble \fI*model\fP,
+	const GLdouble \fI*proj\fP,
+	const GLint \fI*view\fP,
+	GLdouble* \fIobjX\fP,
+	GLdouble* \fIobjY\fP,
+	GLdouble* \fIobjZ\fP )
+.fi
+
+.EQ
+delim $$
+.EN
+.SH PARAMETERS
+.TP \w'\f2winX\fP\ \f2winY\fP\ \f2winZ\fP\ \ 'u 
+\f2winX\fP, \f2winY\fP, \f2winZ\fP
+Specify the window coordinates to be mapped.
+.TP
+\f2model\fP
+Specifies the modelview matrix (as from a \f3glGetDoublev\fP call).
+.TP
+\f2proj\fP
+Specifies the projection matrix (as from a \f3glGetDoublev\fP call).
+.TP
+\f2view\fP
+Specifies the viewport (as from a \f3glGetIntegerv\fP call).
+.TP
+\f2objX\fP, \f2objY\fP, \f2objZ\fP
+Returns the computed object coordinates.
+.SH DESCRIPTION
+\%\f3gluUnProject\fP maps the specified window coordinates into object 
+coordinates using \f2model\fP, \f2proj\fP, and \f2view\fP.
+The result is stored in \f2objX\fP, \f2objY\fP, and \f2objZ\fP. A return value of 
+\%\f3GL_TRUE\fP indicates success; a return value of \%\f3GL_FALSE\fP
+indicates failure.
+.P
+To compute the coordinates (\f2objX\fP, \f2objY\fP, and \f2objZ\fP),
+\%\f3gluUnProject\fP multiplies the normalized device coordinates by the inverse of
+\f2model\fP*\f2proj\fP as follows:
+
+.P
+.ce
+.EQ
+left ( down 70 {cpile { ~"objX" above ~"objY" above ~"objZ"
+above ~W}} ~~ right ) ~=~ INV(P M) 
+left ( down 140 {cpile { 
+{ {2("winX" ~-~ "view"[0])} over {"view" [2]} ~-~ 1 }
+above 
+{ {2("winY" ~-~ "view"[1])} over {"view"[3]} ~-~ 1 }
+above 
+{ 2("winZ") ~-~ 1 }
+above 
+1}} ~~ right )
+.EN
+.bp
+$INV()$ denotes matrix inversion. 
+W is an unused variable, included for consistent matrix notation.
+.SH SEE ALSO
+\f3glGet(3G)\fP, \%\f3gluProject(3G)\fP