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GLUUNPROJECT(3G)                                                                            GLUUNPROJECT(3G)

       gluUnProject - map window coordinates to object coordinates

       GLint gluUnProject( GLdouble winX,
                           GLdouble winY,
                           GLdouble winZ,
                           const GLdouble *model,
                           const GLdouble *proj,
                           const GLint *view,
                           GLdouble* objX,
                           GLdouble* objY,
                           GLdouble* objZ )

       winX, winY, winZ
                       Specify the window coordinates to be mapped.

       model           Specifies the modelview matrix (as from a glGetDoublev call).

       proj            Specifies the projection matrix (as from a glGetDoublev call).

       view            Specifies the viewport (as from a glGetIntegerv call).

       objX, objY, objZ
                       Returns the computed object coordinates.

       gluUnProject  maps  the  specified  window coordinates into object coordinates using model, proj, and
       view.  The result is stored in objX, objY, and objZ. A return value of GL_TRUE indicates  success;  a
       return value of GL_FALSE indicates failure.

       To  compute  the  coordinates  (objX,  objY, and objZ), gluUnProject multiplies the normalized device
       coordinates by the inverse of model*proj as follows:

                                2(winX - view[0])
                                -----------------  - 1

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


       INV() denotes matrix inversion.  W is an unused variable, included for consistent matrix notation.

       glGet(3G), gluProject(3G)


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