extensions/AMD/AMD_blend_minmax_factor.txt

Name

    AMD_blend_minmax_factor


Name Strings

    GL_AMD_blend_minmax_factor


Contributors

    Graham Sellers
    Pierre Boudier

Contact

    Graham Sellers, AMD (graham.sellers 'at' amd.com)


Status

    Shipping.


Version

    Last Modified Date:         April 8, 2011
    Author Revision:            3


Number

    404

Dependencies

    The extension is written against the OpenGL 4.1 (Core) Specification.

    OpenGL 1.0 is required.

Overview

    The EXT_blend_minmax extension extended the GL's blending functionality
    to allow the blending equation to be specified by the application. That
    extension introduced the MIN_EXT and MAX_EXT blend equations, which caused the
    result of the blend equation to become the minimum or maximum of the source
    color and destination color, respectively.

    The MIN_EXT and MAX_EXT blend equations, however, do not include the source
    or destination blend factors in the arguments to the min and max functions.
    This extension provides two new blend equations that produce the minimum
    or maximum of the products of the source color and source factor, and the
    destination color and destination factor.

New Procedures and Functions

    None.

New Tokens

    Accepted by the <mode> parameter of BlendEquation and BlendEquationi, and by
    the <modeRGB> and <modeAlpha> parameters of BlendEquationSeparate and
    BlendEquationSeparatei:

        FACTOR_MIN_AMD                              0x901C
        FACTOR_MAX_AMD                              0x901D

Additions to Chapter 2 of the OpenGL 4.1 (Core) Specification (OpenGL Operation)

    None.

Additions to Chapter 3 of the OpenGL 4.1 (Core) Specification (Rasterization)

    None.

Additions to Chapter 4 of the OpenGL 4.1 (Core) Specification (Per-Fragment
Operations and the Frame Buffer)

    Modify the list of accepted tokens for <mode>, <modeRGB> and <modeAlpha>
    in the description of BlendEquation{i} and BlendEquationSeparate{i}, p.262:

    "... <mode>, <modeRGB>, <modeAlpha> must be one of FUNC_ADD, FUNC_SUBTRACT,
    FUNC_REVERSE_SUBTRACT, MIN, MAX, FACTOR_MIN_AMD, or FACTOR_MAX_AMD. ..."

    Add to Table 4.1: RGB and Alpha Blend Equations

    +-----------------+---------------------------+-----------------------------+
    | Mode            | RGB Components            | Alpha Component             |
    +-----------------+---------------------------+-----------------------------+
    | FACTOR_MIN_AMD  | R = min(Rs * Sr, Rd * Dr) | A = min(As * Sa, Ad * Da)   |
    |                 | G = min(Gs * Sg, Gd * Dg) |                             |
    |                 | B = min(Bs * Sb, Bd * Db) |                             |
    +-----------------+---------------------------+-----------------------------+
    | FACTOR_MAX_AMD  | R = max(Rs * Sr, Rd * Dr) | A = max(As * Sa, Ad * Da)   |
    |                 | G = max(Gs * Sg, Gd * Dg) |                             |
    |                 | B = max(Bs * Sb, Bd * Db) |                             |
    +-----------------+---------------------------+-----------------------------+

Additions to Chapter 5 of the OpenGL 4.1 (Core) Specification (Special Functions)

    None.

Additions to Chapter 6 of the OpenGL 4.1 (Core) Specification (State and
State Requests)

    None.

Additions to Appendix A of the OpenGL 4.1 (Core) Specification (Invariance)

    None.

Additions to the AGL/GLX/WGL Specifications

    None.

Errors

    None.

New State

    Modify Table 6.21: Pixel Operations (cont.) p.343

    Change entries for BLEND_EQUATION_ALPHA and BLEND_EQUATION_RGB to:

    +----------------------+---------+---------------+---------------+-------------------------+-------+
    | Get Value            | Type    | Get Command   | Initial Value | Description             | Sec.  |
    +----------------------+---------+---------------+---------------+-------------------------+-------+
    | BLEND_EQUATION_RGB   | 8* x Z7 | GetIntegeri_v | FUNC_ADD      | RGB Blending Equation   | 4.1.7 |
    |                      |         |               |               | for Draw Buffer i       |       |
    +----------------------+---------+---------------+---------------+-------------------------+-------+
    | BLEND_EQUATION_ALPHA | 8* x Z7 | GetIntegeri_v | FUNC_ADD      | Alpha Blending Equation | 4.1.7 |
    |                      |         |               |               | for Draw Buffer i       |       |
    +----------------------+---------+---------------+---------------+-------------------------+-------+

    * Note that the only change change is that BLEND_EQUATION_RGB and
      BLEND_EQUATION_ALPHA are now Z7 rather than Z5.

Issues

    None, so far.

Revision History

    Rev.    Date      Author    Changes
    ----  --------    --------  -----------------------------------------

     3    04/08/2011  gsellers  Fix typo bug in Table 4.1 (caught by Brian Paul)
     2    09/15/2010  gsellers  Update to stand against OpenGL 4.1
                                Add token values.
                                Rename to AMD_blend_minmax_factor.
     1    03/16/2010  gsellers  Initial draft.