*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->IRIX man pages -> standard/multisample (3)              


multisample(3G)						       multisample(3G)

NAME    [Toc]    [Back]

     multisample - specifies the use of	the multisample	buffer

C SPECIFICATION    [Toc]    [Back]

     void multisample(Boolean bool)

PARAMETERS    [Toc]    [Back]

     bool   is either TRUE or FALSE, indicating	whether	rendering is to	make
	    use	of the multisample buffer or not.  By default multisample is

DESCRIPTION    [Toc]    [Back]

     When multisample is enabled, and multisample buffers exist	in the current
     framebuffer configuration in the current drawmode,	rendered primitives
     directly affect the samples in the	multisample buffer.  Immediately after
     the multisample locations at a pixel are modified,	the front and/or back
     framebuffer colors	are written with the "average" value of	the
     multisample color values.	No change is made to the standard z buffer or
     stencil buffer that may be	associated with	the color buffers, and their
     contents do not affect rendering operation.

     Polygons are sampled into the multisample buffer as much as they are
     sampled into the standard single-sample buffer.  A	single color value is
     computed for the entire pixel, regardless of the number of	samples	at
     that pixel.  Each multisample location is then written with this color,
     if	and only if, it	is geometrically within	the exact polygon boundary.
     If	the Z buffer is	enabled, the correct depth value at each multisample
     location is computed and used to determine	whether	that sample should be
     written or	not.  If stencil is enabled, the test is performed at each
     multisample location.  Framebuffer	modes alpha test, blending, dithering,
     and writemask affect the modification of the individual multisamples, and
     have no effect on the transfer of the "average" color value to the	front
     or	back color buffers.  Alternately, buffer enables frontbuffer,
     backbuffer, leftbuffer, rightbuffer, and zdraw have no effect on the
     modification of the individual multisample	locations; they	affect only
     the transfer of the "average" color value.

     Polygon pattern and line style pattern bits apply equally to all
     multisample locations at a	pixel.	All sample locations are considered
     for modification if the pattern bit is one.  None are considered if the
     pattern bit is zero.

     Lines are sampled into the	multisample buffer as rectangles centered
     around the	exact zero-area	segment.  The rectangle	width is equal to the
     current linewidth.	Its length is exactly equal to the length of the
     segment.  The rectangles of colinear, abutting line segments abut
     exactly, so no multisamples are missed or drawn twice near	the shared

     Points are	sampled	into the multisample buffer as circles centered	around
     the exact point location.	The circle diameter is equal to	the current

									Page 1

multisample(3G)						       multisample(3G)

     Polysmooth, linesmooth, and pointsmooth, must be disabled while
     multisample is enabled, or	rendering results are undefined.

     Text is sampled into the multisample buffer by converting each '1'	in the
     character mask into a 1x1 square, which is	then sampled just like a

     During pixel operations either all	multisample locations at a pixel are
     sampled or	all are	not.

     There are no special clear	commands for the multisample buffer.  Rather,
     the standard clear, zclear, sclear, and czclear commands affect the
     multisample buffer	as much	as they	affect the standard color, stencil,
     and z buffers.  Clear modifies the	enabled	color buffers, and always
     modifies the color	portion	of each	multisample location.  zclear operates
     on	all multisample	z locations.  sclear operates on all multisample
     stencil locations.	 czclear behaves like clear and	zclear,	except that
     the z value is specified.

     When multisample is disabled, but the system is configured	for
     multisample operation, rendering neither affects the multisample buffer,
     nor is it a function of the contents of the multisample buffer.  It is as
     though there were no multisample buffer at	all.  zbuffer, if configured
     and enabled, tests	and updates the	standard z buffer, not the zbuffer
     locations in the multisample buffer.  Likewise stencil, if	configured and
     enabled, tests and	updates	the standard stencil buffer, not the stencil
     locations in the multisample buffer.

     Polysmooth, linesmooth, and pointsmooth are well defined when multisample
     is	false.

     Multisample state is maintained but ignored if no multisample buffer is
     configured.  Because it is	not possible to	allocate a multisample buffer
     in	color index mode, multisample is always	ignored	in color index mode.

     The multisample buffer is a part of the normal framebuffer.  multisample
     should be called only while drawmode is NORMALDRAW, and it	affects
     rendering only while drawmode is NORMALDRAW.

SEE ALSO    [Toc]    [Back]

     msalpha, msmask, mspattern, mssize

BUGS    [Toc]    [Back]

     On	the IRIS-4D RealityEngine model	the values of frontbuffer, backbuffer,
     leftbuffer, and rightbuffer should	not be changed between the time	clear
     or	czclear	are called and the time	that the rendered image	is complete.
     At	least one of the color buffers must be enabled during all use of the
     multisample buffer.

     Points are	in fact	sampled	into the multisample buffer as squares where
     the squre width is	equal to the current pointsize.	 This will be fixed in
     a future release.

									PPPPaaaaggggeeee 2222
[ Back ]
 Similar pages
Name OS Title
mssize IRIX specifies multisample buffer configuration
msmask IRIX specifies a multisample mask
mspattern IRIX specifies a multisample sample pattern
msalpha IRIX specifies treatment of alpha values during multisample rendering
gltagsamplebuffersgix IRIX mark all samples of a multisample buffer
zbsize IRIX specifies the number of bit planes desired to comprise the Z buffer
zfunction IRIX specifies the function used for z-buffer comparison by the current framebuffer
zwritemask IRIX specifies a write mask for the z-buffer of the current framebuffer
getmultisample IRIX returns the current multisample mode
getgconfig IRIX gets the size of a buffer or a state in the current buffer configuration
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service