glupickmatrix man page on Solaris

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GLUPICKMATRIX(3gl)					    GLUPICKMATRIX(3gl)

NAME
       gluPickMatrix - define a picking region

C SPECIFICATION
       void gluPickMatrix( GLdouble x,
			   GLdouble y,
			   GLdouble delX,
			   GLdouble delY,
			   GLint *viewport )

PARAMETERS
       x, y Specify the center of a picking region in window coordinates.

       delX, delY
	    Specify  the width and height, respectively, of the picking region
	    in window coordinates.

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

DESCRIPTION
       gluPickMatrix creates a projection matrix that can be used to  restrict
       drawing to a small region of the viewport.  This is typically useful to
       determine what objects are being drawn near the cursor.	Use gluPickMa‐
       trix  to	 restrict  drawing to a small region around the cursor.	 Then,
       enter selection mode (with glRenderMode) and rerender the  scene.   All
       primitives  that	 would	have been drawn near the cursor are identified
       and stored in the selection buffer.

       The matrix created by gluPickMatrix is multiplied by the current matrix
       just as if glMultMatrix is called with the generated matrix.  To effec‐
       tively use the generated pick matrix for picking, first	call  glLoadI‐
       dentity	to  load an identity matrix onto the perspective matrix stack.
       Then call gluPickMatrix, and finally, call a command (such  as  gluPer‐
       spective) to multiply the perspective matrix by the pick matrix.

       When  using  gluPickMatrix  to  pick  NURBS, be careful to turn off the
       NURBS property GLU_AUTO_LOAD_MATRIX.  If	 GLU_AUTO_LOAD_MATRIX  is  not
       turned  off,  then any NURBS surface rendered is subdivided differently
       with the pick matrix than the way it was subdivided  without  the  pick
       matrix.

EXAMPLE
       When rendering a scene as follows:

       glMatrixMode(GL_PROJECTION);
       glLoadIdentity();
       gluPerspective(...);
       glMatrixMode(GL_MODELVIEW);
       /* Draw the scene */

       a portion of the viewport can be selected as a pick region like this:

       glMatrixMode(GL_PROJECTION);
       glLoadIdentity();
       gluPickMatrix(x, y, width, height, viewport);
       gluPerspective(...);
       glMatrixMode(GL_MODELVIEW);
       /* Draw the scene */

SEE ALSO
       glGet, glLoadIndentity, glMultMatrix, glRenderMode, gluPerspective

				   15 Mar 97		    GLUPICKMATRIX(3gl)
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