Index for Section 3

Alphabetical listing for G

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gluPickMatrix()
NAME
  gluPickMatrix - define a picking region

SYNOPSIS
  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
  gluPickMatrix() 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
  effectively use the generated pick matrix for picking, first call
  glLoadIdentity() to load an identity matrix onto the perspective matrix
  stack. Then call gluPickMatrix(), and finally, call a command (such as
  gluPerspective()) 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(3), glLoadIndentity(3), glMultMatrix(3), glRenderMode(3),
  gluPerspective(3)

Index for Section 3

Alphabetical listing for G

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