NAME
	  glPassThrough	- place	a marker in the	feedback buffer


     C SPECIFICATION
	  void glPassThrough( GLfloat token )


     PARAMETERS
	  token	 Specifies a marker value to be	placed in the feedback
		 buffer	following a GL_PASS_THROUGH_TOKEN.

     DESCRIPTION
	  Feedback is a	GL render mode.	 The mode is selected by
	  calling glRenderMode with GL_FEEDBACK.  When the GL is in
	  feedback mode, no pixels are produced	by rasterization.
	  Instead, information about primitives	that would have	been
	  rasterized is	fed back to the	application using the GL.  See
	  the glFeedbackBuffer reference page for a description	of the
	  feedback buffer and the values in it.

	  glPassThrough	inserts	a user-defined marker in the feedback
	  buffer when it is executed in	feedback mode. token is
	  returned as if it were a primitive; it is indicated with its
	  own unique identifying value:	 GL_PASS_THROUGH_TOKEN.	 The
	  order	of glPassThrough commands with respect to the
	  specification	of graphics primitives is maintained.

     NOTES
	  glPassThrough	is ignored if the GL is	not in feedback	mode.

     ERRORS
	  GL_INVALID_OPERATION is generated if glPassThrough is
	  executed between the execution of glBegin and	the
	  corresponding	execution of glEnd.

     ASSOCIATED	GETS
	  glGet	with argument GL_RENDER_MODE

     SEE ALSO
	  glFeedbackBuffer, glRenderMode