glRenderMode(3G)	       OpenGL Reference		      glRenderMode(3G)

NAME    [Toc]    [Back]

     glRenderMode - set	rasterization mode

C SPECIFICATION    [Toc]    [Back]

     GLint glRenderMode( GLenum	mode )

PARAMETERS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     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 had been 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 if	the render mode	had 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	     0.

     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.

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






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glRenderMode(3G)	       OpenGL Reference		      glRenderMode(3G)

NOTES    [Toc]    [Back]

     If	an error is generated, glRenderMode returns 0 regardless of the
     current render mode.

     One particularly surprising error condition occurs	when the selection or
     feedback buffer is	too large for the implementation to handle.  The
     problem might not be detected until glRenderMode is executed, because
     buffer memory might not be	allocated or locked down until that time.  In
     such a case, it is	possible that the only indication of the error is that
     glRenderMode will return zero.  Thus it is	especially important to	check
     the return	value.

ERRORS    [Toc]    [Back]

     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    [Toc]    [Back]

     glGet with	argument GL_RENDER_MODE

SEE ALSO    [Toc]    [Back]

     glFeedbackBuffer, glInitNames, glLoadName,	glPassThrough, glPushName,
     glSelectBuffer


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