GLSELECTBUFFER(3G)						   OpenGL Manual						GLSELECTBUFFER(3G)

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(), glPushName()) 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(emthat 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 followed 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, resets the overflow flag and the selection buffer pointer, and
       initializes 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.  glWindowPos() will always generate a selection hit.

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

       glGet() with argument GL_SELECTION_BUFFER_SIZE

       glGetPointerv() with argument GL_SELECTION_BUFFER_POINTER

SEE ALSO

       glFeedbackBuffer(), glInitNames(), glLoadName(), glPushName(), glRenderMode()

COPYRIGHT

       Copyright (C) 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see
       http://oss.sgi.com/projects/FreeB/.

AUTHORS

       opengl.org

opengl.org							    06/10/2014							GLSELECTBUFFER(3G)