- Method gluPickMatrix
void gluPickMatrix(float x, float y, float width, float height, array(int) viewport)
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 GL.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 GL.glMultMatrix is called with the generated matrix. To effectively use the generated pick matrix for picking, first call GL.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.
- Parameter viewport
The viewport is an array with four integers.
Does the NURB remark apply?
- See also
GL.glGet, gluLoadIdentity, gluMultMatrix, gluRenderMode, gluPerspective