GL_NV_blend_square

Name

    NV_blend_square

Name Strings

    GL_NV_blend_square

Contact

    Matt Craighead, NVIDIA Corporation (mcraighead 'at' nvidia.com)
    Mark J. Kilgard, NVIDIA Corporation (mjk 'at' nvidia.com)

Notice

    Copyright NVIDIA Corporation, 1999.

Status

    Shipping (version 1.1)

Version

    Date: 1/14/2000  Version: 1.1
    $Date$ $Revision$

Number

    194

Dependencies

    Written based on the wording of the OpenGL 1.2.1 specification.

Overview

    It is useful to be able to multiply a number by itself in the blending
    stages -- for example, in certain types of specular lighting effects
    where a result from a dot product needs to be taken to a high power.

    This extension provides four additional blending factors to permit
    this and other effects: SRC_COLOR and ONE_MINUS_SRC_COLOR for source
    blending factors, and DST_COLOR and ONE_MINUS_DST_COLOR for destination
    blending factors.

    Direct3D provides capability bits for advertising these additional
    blend modes.

Issues

    None

New Procedures and Functions

    None

New Tokens

    None

Additions to Chapter 2 of the OpenGL 1.2.1 Specification (OpenGL Operation)

    None

Additions to Chapter 3 of the OpenGL 1.2.1 Specification (Rasterization)

    None

Additions to Chapter 4 of the OpenGL 1.2.1 Specification (Per-Fragment Operations and the Framebuffer)

    Two lines are added to each of tables 4.1 and 4.2:

        Value                           Blend Factors
        -----                           -------------
        ZERO                            (0, 0, 0, 0)
        ONE                             (1, 1, 1, 1)
        SRC_COLOR                       (Rs, Gs, Bs, As)                                        NEW
        ONE_MINUS_SRC_COLOR             (1, 1, 1, 1) - (Rs, Gs, Bs, As)                         NEW
        DST_COLOR                       (Rd, Gd, Bd, Ad)
        ONE_MINUS_DST_COLOR             (1, 1, 1, 1) - (Rd, Gd, Bd, Ad)
        SRC_ALPHA                       (As, As, As, As) / Ka
        ONE_MINUS_SRC_ALPHA             (1, 1, 1, 1) - (As, As, As, As) / Ka
        DST_ALPHA                       (Ad, Ad, Ad, Ad) / Ka
        ONE_MINUS_DST_ALPHA             (1, 1, 1, 1) - (Ad, Ad, Ad, Ad) / Ka
        CONSTANT_COLOR                  (Rc, Gc, Bc, Ac)
        ONE_MINUS_CONSTANT_COLOR        (1, 1, 1, 1) - (Rc, Gc, Bc, Ac)
        CONSTANT_ALPHA                  (Ac, Ac, Ac, Ac)
        ONE_MINUS_CONSTANT_ALPHA        (1, 1, 1, 1) - (Ac, Ac, Ac, Ac)
        SRC_ALPHA_SATURATE              (f, f, f, 1)

        Table 4.1: Values controlling the source blending function and the
        source blending values they compute.  f = min(As, 1 - Ad).

        Value                           Blend Factors
        -----                           -------------
        ZERO                            (0, 0, 0, 0)
        ONE                             (1, 1, 1, 1)
        SRC_COLOR                       (Rs, Gs, Bs, As)
        ONE_MINUS_SRC_COLOR             (1, 1, 1, 1) - (Rs, Gs, Bs, As)
        DST_COLOR                       (Rd, Gd, Bd, Ad)                                        NEW
        ONE_MINUS_DST_COLOR             (1, 1, 1, 1) - (Rd, Gd, Bd, Ad)                         NEW
        SRC_ALPHA                       (As, As, As, As) / Ka
        ONE_MINUS_SRC_ALPHA             (1, 1, 1, 1) - (As, As, As, As) / Ka
        DST_ALPHA                       (Ad, Ad, Ad, Ad) / Ka
        ONE_MINUS_DST_ALPHA             (1, 1, 1, 1) - (Ad, Ad, Ad, Ad) / Ka
        CONSTANT_COLOR_EXT              (Rc, Gc, Bc, Ac)
        ONE_MINUS_CONSTANT_COLOR_EXT    (1, 1, 1, 1) - (Rc, Gc, Bc, Ac)
        CONSTANT_ALPHA_EXT              (Ac, Ac, Ac, Ac)
        ONE_MINUS_CONSTANT_ALPHA_EXT    (1, 1, 1, 1) - (Ac, Ac, Ac, Ac)

        Table 4.2: Values controlling the destination blending function and
        the destination blending values they compute.

Additions to Chapter 5 of the OpenGL 1.2.1 Specification (Special Functions)

    None

Additions to Chapter 6 of the OpenGL 1.2.1 Specification (State and State Requests)

    None

Additions to the AGL/GLX/WGL Specifications

    None

GLX Protocol

    None

Errors

    None

New State

(table 6.15, page 205)
    Get Value                 Type  Get Command   Initial Value   Sec    Attribute
    ------------------------  ----  ------------  -------------   -----  ---------
    BLEND_SRC                  Z15  GetIntegerv        ONE        4.1.6  color-buffer
    BLEND_DST                  Z14  GetIntegerv        ZERO       4.1.6  color-buffer

NOTE: the only change is that Z13 changes to Z15 and Z12 changes to Z14

New Implementation Dependent State

    None

Revision History

    None

Implementation Support

   List of OpenGL implementations supporting the GL_NV_blend_square extension

Original File

   Original text file for the GL_NV_blend_square extension