gluUnProject  -  map  window coordinates to object coordi-
       nates



C SPECIFICATION

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



PARAMETERS

       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 glGet-
                       Integerv call).

       objX, objY, objZ
                       Returns the computed object coordinates.


DESCRIPTION

       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:






















                    objY
                                  __w_i_n<I>v_Y<I>i_<I>e_v<I>w_i_e_w_____-1








                   (    )=INV(PM)(                 )









                    objZ
                                      2(winZ)-1


















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