'\" e  
'\"macro stdmacro
.ds Vn Version 1.2
.ds Dt 6 March 1997
.ds Re Release 1.2.0
.ds Dp May 22 14:54
.ds Dm 4 May 22 14:
.ds Xs 13294     5
.TH GLUUNPROJECT4 3G
.SH NAME
.B "gluUnProject4
\- map window and clip coordinates to object coordinates

.SH C SPECIFICATION
GLint \f3gluUnProject4\fP(
GLdouble \fIwinX\fP,
.nf
.ta \w'\f3GLint \fPgluUnProject4( 'u
	GLdouble \fIwinY\fP,
	GLdouble \fIwinZ\fP,
	GLdouble \fIclipW\fP,
	const GLdouble \fI*model\fP,
	const GLdouble \fI*proj\fP,
	const GLint \fI*view\fP,
	GLdouble \fInear\fP,
	GLdouble \fIfar\fP,
	GLdouble* \fIobjX\fP,
	GLdouble* \fIobjY\fP,
	GLdouble* \fIobjZ\fP,
	GLdouble* \fIobjW\fP )
.fi

.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
\f2clipW\fP
Specify the clip w coordinate 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
\f2near\fP, \f2far\fP
Specifies the near and far planes (as from a \f3glGetDoublev\fP call).
.TP
\f2objX\fP, \f2objY\fP, \f2objZ\fP, \f2objW\fP
Returns the computed object coordinates.
.SH DESCRIPTION
\%\f3gluUnProject4\fP maps the specified window coordinates \f2winX\fP, \f2winY\fP and \f2winZ\fP
and its clip w coordinate \f2clipW\fP
into object 
coordinates (\f2objX\fP, \f2objY\fP, \f2objZ\fP, \f2objW\fP)
using \f2model\fP, \f2proj\fP and \f2view\fP. \f2clipW\fP can be other than
1 as for vertices in \f3glFeedbackBuffer\fP when data type 
\%\f3GL_4D_COLOR_TEXTURE\fP is returned.
This also handles the case
where the \f2near\fP and \f2far\fP planes are different from the default,
0 and 1, respectively.
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, \f2objZ\fP and \f2objW\fP),
\%\f3gluUnProject4\fP multiplies the normalized device coordinates by the inverse of
\f2model\fP*\f2proj\fP as follows:

.Bd -literal
                         2(winX - view[0])
                         -----------------  - 1
                              view[2]

    objX                 2(winY - view[1])
    objY   =  INV(PM)    -----------------  - 1
    objZ                      view[3]
     W
                           2(winZ - near)
                         -----------------  - 1
                             (far - near)

                               clipW
.Ed

.sp
INV() denotes matrix inversion. 
.P
\%\f3gluUnProject4\fP is equivalent to \%\f3gluUnProject\fP when \f2clipW\fP is 1, \f2near\fP is 0 and
\f2far\fP is 1.
.SH NOTES
\%\f3gluUnProject4\fP is available only if the GLU version is 1.3 or greater.
.SH SEE ALSO
\f3glGet\fP,
\f3glFeedbackBuffer\fP,
\%\f3gluProject\fP,
\%\f3gluUnProject\fP