Hackers Magazine 57/CdHackersMagazineNr57.iso/Software/Multimedia/k3d-setup-0.7.11.0.exe/lib/site-packages/OpenGL/raw/GL/EXT/framebuffer_multisample.py

Python Source | 2008-12-07 | 5.1 KB | 102 lines

'''OpenGL extension EXT.framebuffer_multisample

Overview (from the spec)

    This extension extends the EXT_framebuffer_object framework to
    enable multisample rendering.

    The new operation RenderbufferStorageMultisampleEXT() allocates
    storage for a renderbuffer object that can be used as a multisample
    buffer.  A multisample render buffer image differs from a
    single-sample render buffer image in that a multisample image has a
    number of SAMPLES that is greater than zero.  No method is provided
    for creating multisample texture images.

    All of the framebuffer-attachable images attached to a framebuffer
    object must have the same number of SAMPLES or else the framebuffer
    object is not "framebuffer complete".  If a framebuffer object with
    multisample attachments is "framebuffer complete", then the
    framebuffer object behaves as if SAMPLE_BUFFERS is one.

    In traditional multisample rendering, where
    DRAW_FRAMEBUFFER_BINDING_EXT is zero and SAMPLE_BUFFERS is one, the
    GL spec states that "the color sample values are resolved to a
    single, displayable color each time a pixel is updated."  There are,
    however, several modern hardware implementations that do not
    actually resolve for each sample update, but instead postpones the
    resolve operation to a later time and resolve a batch of sample
    updates at a time.  This is OK as long as the implementation behaves
    "as if" it had resolved a sample-at-a-time. Unfortunately, however,
    honoring the "as if" rule can sometimes degrade performance.

    In contrast, when DRAW_FRAMEBUFFER_BINDING_EXT is an
    application-created framebuffer object, MULTISAMPLE is enabled, and
    SAMPLE_BUFFERS is one, there is no implicit per-sample-update
    resolve.  Instead, the application explicitly controls when the
    resolve operation is performed.  The resolve operation is affected
    by calling BlitFramebufferEXT (provided by the EXT_framebuffer_blit
    extension) where the source is a multisample application-created
    framebuffer object and the destination is a single-sample
    framebuffer object (either application-created or window-system
    provided).

    This design for multisample resolve more closely matches current
    hardware, but still permits implementations which choose to resolve
    a single sample at a time.  If hardware that implementes the
    multisample resololution "one sample at a time" exposes
    EXT_framebuffer_multisample, it could perform the implicit resolve
    to a driver-managed hidden surface, then read from that surface when
    the application calls BlitFramebufferEXT.

    Another motivation for granting the application explicit control
    over the multisample resolve operation has to do with the
    flexibility afforded by EXT_framebuffer_object.  Previously, a
    drawable (window or pbuffer) had exclusive access to all of its
    buffers.  There was no mechanism for sharing a buffer across
    multiple drawables.  Under EXT_framebuffer_object, however, a
    mechanism exists for sharing a framebuffer-attachable image across
    several framebuffer objects, as well as sharing an image between a
    framebuffer object and a texture.  If we had retained the "implicit"
    resolve from traditional multisampled rendering, and allowed the
    creation of "multisample" format renderbuffers, then this type of
    sharing would have lead to two problematic situations:

      * Two contexts, which shared renderbuffers, might perform
        competing resolve operations into the same single-sample buffer
        with ambiguous results.

      * It would have introduced the unfortunate ability to use the
        single-sample buffer as a texture while MULTISAMPLE is ENABLED.

    By using the BlitFramebufferEXT from EXT_framebuffer_blit as an
    explicit resolve to serialize access to the multisampeld contents
    and eliminate the implicit per-sample resolve operation, we avoid
    both of these problems.

The official definition of this extension is available here:
    http://oss.sgi.com/projects/ogl-sample/registry/EXT/framebuffer_multisample.txt

Automatically generated by the get_gl_extensions script, do not edit!
'''
from OpenGL import platform, constants, constant, arrays
from OpenGL import extensions
from OpenGL.GL import glget
import ctypes
EXTENSION_NAME = 'GL_EXT_framebuffer_multisample'
GL_RENDERBUFFER_SAMPLES_EXT = constant.Constant( 'GL_RENDERBUFFER_SAMPLES_EXT', 0x8CAB )
GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT = constant.Constant( 'GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT', 0x8D56 )
GL_MAX_SAMPLES_EXT = constant.Constant( 'GL_MAX_SAMPLES_EXT', 0x8D57 )
glRenderbufferStorageMultisampleEXT = platform.createExtensionFunction(
    'glRenderbufferStorageMultisampleEXT', dll=platform.GL,
    extension=EXTENSION_NAME,
    resultType=None,
    argTypes=(constants.GLenum, constants.GLsizei, constants.GLenum, constants.GLsizei, constants.GLsizei,),
    doc = 'glRenderbufferStorageMultisampleEXT( GLenum(target), GLsizei(samples), GLenum(internalformat), GLsizei(width), GLsizei(height) ) -> None',
    argNames = ('target', 'samples', 'internalformat', 'width', 'height',),
)


def glInitFramebufferMultisampleEXT():
    '''Return boolean indicating whether this extension is available'''
    return extensions.hasGLExtension( EXTENSION_NAME )