glRenderMode.3gl

Name

  glRenderMode - set rasterization mode

C Specification

  GLint	glRenderMode( GLenum mode )

Parameters

  mode	Specifies the rasterization mode.  Three values	are accepted:
	GL_RENDER, GL_SELECT, and GL_FEEDBACK.	The default value is
	GL_RENDER.

Description

  glRenderMode sets the	rasterization mode.  It	takes one argument, mode,
  which	can assume one of three	predefined values:

  GL_RENDER	  Render mode. Primitives are rasterized, producing pixel
		  fragments, which are written into the	frame buffer.  This
		  is the normal	mode and also the default mode.

  GL_SELECT	  Selection mode.  No pixel fragments are produced, and	no
		  change to the	frame buffer contents is made.	Instead, a
		  record of the	names of primitives that would have been
		  drawn	if the render mode was GL_RENDER is returned in	a
		  select buffer, which must be created (see glSelectBuffer)
		  before selection mode	is entered.

  GL_FEEDBACK	  Feedback mode.  No pixel fragments are produced, and no
		  change to the	frame buffer contents is made.	Instead, the
		  coordinates and attributes of	vertices that would have been
		  drawn	had the	render mode been GL_RENDER is returned in a
		  feedback buffer, which must be created (see
		  glFeedbackBuffer) before feedback mode is entered.

  The return value of glRenderMode is determined by the	render mode at the
  time glRenderMode is called, rather than by mode.  The values	returned for
  the three render modes are as	follows:

  GL_RENDER	  Zero.

  GL_SELECT	  The number of	hit records transferred	to the select buffer.

  GL_FEEDBACK	  The number of	values (not vertices) transferred to the
		  feedback buffer.

  Refer	to the glSelectBuffer and glFeedbackBuffer reference pages for more
  details concerning selection and feedback operation.

Notes

  If an	error is generated, glRenderMode returns zero regardless of the
  current render mode.

Errors

  GL_INVALID_ENUM is generated if mode is not one of the three accepted
  values.

  GL_INVALID_OPERATION is generated if glSelectBuffer is called	while the
  render mode is GL_SELECT, or if glRenderMode is called with argument
  GL_SELECT before glSelectBuffer is called at least once.

  GL_INVALID_OPERATION is generated if glFeedbackBuffer	is called while	the
  render mode is GL_FEEDBACK, or if glRenderMode is called with	argument
  GL_FEEDBACK before glFeedbackBuffer is called	at least once.

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

Associated Gets

  glGet	with argument GL_RENDER_MODE

See Also

  glFeedbackBuffer, glInitNames, glLoadName, glPassThrough, glPushName,
  glSelectBuffer

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Last Edited: Fri Dec 6 11:18:03 EST 1996 by AFV
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