glScissor.3gl







Name

  glScissor - define the scissor box





C Specification

  void glScissor( GLint	x,

		  GLint	y,

		  GLsizei width,

		  GLsizei height )





Parameters



  x, y Specify the lower left corner of	the scissor box.  Initially (0,0).



  width, height

       Specify the width and height of the scissor box.	 When a	GL context is

       first attached to a window, width and height are	set to the dimensions

       of that window.





Description

  The glScissor	routine	defines	a rectangle, called the	scissor	box, in

  window coordinates.  The first two arguments,	x and y, specify the lower

  left corner of the box.  width and height specify the	width and height of

  the box.



  The scissor test is enabled and disabled using glEnable and glDisable	with

  argument GL_SCISSOR_TEST.  While the scissor test is enabled,	only pixels

  that lie within the scissor box can be modified by drawing commands.

  Window coordinates have integer values at the	shared corners of frame

  buffer pixels, so  glScissor(0,0,1,1)	allows only the	lower left pixel in

  the window to	be modified,  and glScissor(0,0,0,0) disallows modification

  to all pixels	in the window.



  When the scissor test	is disabled, it	is as though the scissor box includes

  the entire window.



Errors

  GL_INVALID_VALUE is generated	if either width	or height is negative.



  GL_INVALID_OPERATION is generated if glScissor is executed between

  execution of glBegin and the corresponding execution ofglEnd.



Associated Gets

  glGet	with argument GL_SCISSOR_BOX

  glIsEnabled with argument GL_SCISSOR_TEST



See Also

  glEnable, glViewport








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Last Edited: Tue, May 23, 1995

AFV