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'''OpenGL extension SGIS.shared_multisample
This module customises the behaviour of the
OpenGL.raw.GLX.SGIS.shared_multisample to provide a more
Python-friendly API
Overview (from the spec)
While the OpenGL multisample extension (SGIS_multisample) provides
good out-of-order antialiasing via subpixel samples, multisample
hardware is very expensive because it multiplies the per-pixel
framebuffer memory required to maintain color, depth, and stencil
state by the number of samples.
The cost-sensitive Location Based Entertainment (LBE) market
desires good quality antialiasing, but the cost of maintaining
multisample memory for every pixel in the framebuffer managed area
is often prohibitive. Low-end multi-channel visual simulation may
have similar cost constraints.
LBE applications typically render several channels that are output
to different video display devices. For example, an LBE
application may render four 800x600 resolution channels, one per
game player. While the total managed area may be 1600x1200, each
channel ends up being rendered serially. With traditional
multisampling (as specified by SGIS_multisample), multisample
memory must be retained across the entire 1600x1200 managed area
though in fact the application is never using more than an 800x600
rectangle of multisample pixel state at any given time.
This sharing of multisample framebuffer state can result in a
substantial competitive advantage for high-end multi-channel
multisampling hardware for LBE applications. Unlike a "cheap PC
per seat" solution, a high-end solution can be amortized by sharing
both texture and multisample memory between the multiple channels
(as well as host resources such as disk and CPUs). For cheap PCs
to have the same amount of texture memory and quality of
antialiasing, texture and multisample memory have to be replicated
in every PC.
In a typical windowed environment, the entire framebuffer managed
area must retain multisample state because windows can be moved
dynamically and resized (up to the entire size of the managed
area). For LBE applications though, the layout of channel
subrectangles in the framebuffer managed area is static and the
LBE application monopolizes the graphics device (no other
concurrent windowed apps). Because of their channel-oriented,
dedicated, cost-sensitive nature, LBE applications can benefit from
a means to share the available multisample memory resources among
all the channels.
The SGIS_shared_multisample extension specifies a single
multisample buffer subrectangle sized smaller than the total
managed area that is both shared among multiple windows and
repositionable within in a window.
Use of the SGIS_shared_multisample extension is predicated on
specially configuring the window system, typically via a command
line option added to the window system server's startup command.
When run in this mode, OpenGL applications will see the
GL_SGIS_shared_multisample string advertised in the GL_EXTENSIONS
string (along with the GL_SGIS_multisample string). In this mode,
the behavior of multisample extension changes. Instead of the
multisample buffer memory being retained per-pixel across the
entire managed area, multisample memory is shared among multisample
windows and repositionable within a multisample window.
Switching windows or repositioning the multisample subrectangle
will make undefined the shared state within the multisample, depth,
stencil, and accumulation buffers.
When rendering into a multisample window, fragments that fall
outside the window's multisample subrectangle are discarded
(scissored). By default, the window's multisample rectangle is
positioned at its window origin.
The official definition of this extension is available here:
http://www.opengl.org/registry/specs/SGIS/shared_multisample.txt
'''
from OpenGL import platform, constant, arrays
from OpenGL import extensions, wrapper
import ctypes
from OpenGL.raw.GLX import _types, _glgets
from OpenGL.raw.GLX.SGIS.shared_multisample import *
from OpenGL.raw.GLX.SGIS.shared_multisample import _EXTENSION_NAME
def glInitSharedMultisampleSGIS():
'''Return boolean indicating whether this extension is available'''
from OpenGL import extensions
return extensions.hasGLExtension( _EXTENSION_NAME )
### END AUTOGENERATED SECTION
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