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GLSELECTBUFFER()					      GLSELECTBUFFER()

NAME
       glSelectBuffer -	establish a buffer for selection mode values

C SPECIFICATION
       void glSelectBuffer( GLsizei size,
			    GLuint *buffer )

PARAMETERS
       size    Specifies the size of buffer.

       buffer  Returns the selection data.

DESCRIPTION
       glSelectBuffer  has  two	 arguments: buffer is a	pointer	to an array of
       unsigned	integers, and size indicates the size of  the  array.	buffer
       returns	values	from  the name stack (see glInitNames, glLoadName, gl-
       PushName) when the rendering  mode  is  GL_SELECT  (see	glRenderMode).
       glSelectBuffer  must be issued before selection mode is enabled,	and it
       must not	be issued while	the rendering mode is GL_SELECT.

       A programmer can	use selection to determine which primitives are	 drawn
       into  some  region  of  a window.  The region is	defined	by the current
       modelview and perspective matrices.

       In selection mode, no pixel fragments are produced from	rasterization.
       Instead,	 if  a	primitive or a raster position intersects the clipping
       volume defined by the viewing frustum  and  the	user-defined  clipping
       planes,	this primitive causes a	selection hit.	(With polygons,	no hit
       occurs if the polygon is	culled.)  When a change	is made	 to  the  name
       stack, or when glRenderMode is called, a	hit record is copied to	buffer
       if any hits have	occurred since the last	such event (name stack	change
       or  glRenderMode	call).	The hit	record consists	of the number of names
       in the name stack at the	time of	the event, followed by the minimum and
       maximum depth values of all vertices that hit since the previous	event,
       followed	by the name stack contents, bottom name	first.

       Depth values (which are in the range [0,1]) are multiplied by 2^32 - 1,
       before being placed in the hit record.

       An  internal index into buffer is reset to 0 whenever selection mode is
       entered.	 Each time a hit record	is copied into buffer,	the  index  is
       incremented  to	point  to  the	cell just past the end of the block of
       names - that is,	to the next available cell.   If  the  hit  record  is
       larger  than  the number	of remaining locations in buffer, as much data
       as can fit is copied, and the overflow flag is set.  If the name	 stack
       is  empty  when	a hit record is	copied,	that record consists of	0 fol-
       lowed by	the minimum and	maximum	depth values.

       To exit selection mode, call glRenderMode with an argument  other  than
       GL_SELECT.   Whenever  glRenderMode  is called while the	render mode is
       GL_SELECT, it returns the number	of hit records copied to  buffer,  re-
       sets  the  overflow flag	and the	selection buffer pointer, and initial-
       izes the	name stack to be empty.	 If the	 overflow  bit	was  set  when
       glRenderMode was	called,	a negative hit record count is returned.

NOTES
       The  contents  of buffer	is undefined until glRenderMode	is called with
       an argument other than GL_SELECT.

       glBegin/glEnd primitives	and calls to glRasterPos can result in hits.

ERRORS
       GL_INVALID_VALUE	is generated if	size is	negative.

       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 glSelectBuffer is executed between
       the execution of	glBegin	and the	corresponding execution	of glEnd.

ASSOCIATED GETS
       glGet with argument GL_NAME_STACK_DEPTH

SEE ALSO
       glFeedbackBuffer, glInitNames, glLoadName, glPushName, glRenderMode

							      GLSELECTBUFFER()

NAME | C SPECIFICATION | PARAMETERS | DESCRIPTION | NOTES | ERRORS | ASSOCIATED GETS | SEE ALSO

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