XXX - Not complete yet!!!

Name

    SGIX_occlusion_instrument

Name Strings

    GL_SGIX_occlusion_instrument

Version

    $Date: 1998/04/21 03:53:34 $ $Revision: 1.1 $

Number

    151

Dependencies

    SGIX_intruments is required

Overview

    This extension defines an occlusion instrument that can be used by
    applications to determine whether a set of fragments are completely
    occluded (i.e., fail the depth test) by fragments already in the
    frame buffer.

Issues

    * This extension is named like this so that developers have a better
      idea of what the extension does instead of being obscured by a
      device-specific name.  The extension encompasses functionality that
      is exposed by the bali_r_extension, but it does not try to address
      the different mode of retrieving occlusion information.  It's
      possible that Bali may not be able to support this extension easily.


New Procedures and Functions

    None

New Tokens

    Accepted by the <cap> parameter of Enable, Disable and IsEnabled:

	OCCLUSION_INSTRUMENT_SGIX		0x6060

Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation)

    None.

Additions to Chapter 3 of the 1.1 Specification (Rasterization)

    None.

Additions to Chapter 4 of the 1.1 Specification (Per-Fragment Operations
and the Frame Buffer)

    Added to subsection 4.1.5 (Depth buffer test) at the end of the
    paragraph which begins "If the depth buffer test fails...":

    If OCCLUSION_INSTRUMENT_SGIX is enabled and instruments have been
    started via a call to StartInstrumentSGIX, a flag is maintained
    of whether fragments pass or fail the depth test.  The flag's initial
    state is TRUE and it is set to FALSE whenever a fragment generated
    during rasterization passes the depth test.

    The format of the measured occlusion instrument consists of four
    words:  the occlusion instrument enable enum (OCCLUSION_INSTRUMENT_SGIX);
    the size of the measurement (4); the result of the measurement; and
    the marker passed in with either StopInstrumentsSGIX or
    ReadInstrumentsSGIX.

Additions to Chapter 5 of the 1.1 Specification (Special Functions)

Additions to Chapter 6 of the 1.1 Specification (State and State Requests)

Additions to the GLX Specification


Errors

New State

New Implementation Dependent State