gluUnProject(3G)	       OpenGL Reference		      gluUnProject(3G)

NAME    [Toc]    [Back]

     gluUnProject - map	window coordinates to object coordinates

C SPECIFICATION    [Toc]    [Back]

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

PARAMETERS    [Toc]    [Back]

     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.

DESCRIPTION    [Toc]    [Back]

     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:

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




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gluUnProject(3G)	       OpenGL Reference		      gluUnProject(3G)



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

SEE ALSO    [Toc]    [Back]

     glGet, gluProject


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