Name

    ATI_texture_env_combine3

Name Strings

    GL_ATI_texture_env_combine3

Contact

    Evan Hart, ATI Corporation (ehart 'at' ati.com)
    Dan Ginsburg, ATI Corporation (dginsbur 'at' ati.com)

Notice

    Copyright ATI Corporation, 2002.

IP Status

    None.

Version

    Date: 8/02/2002 Revision: 1.01
    
Number

    None.

Dependencies

    ARB_texture_env_combine is required and is modified by this extension
    ARB_multitexture affects the definition of this extension

Overview

    Adds new set of operations to the texture combiner operations.

    MODULATE_ADD_ATI               Arg0 * Arg2 + Arg1
    MODULATE_SIGNED_ADD_ATI        Arg0 * Arg2 + Arg1 - 0.5
    MODULATE_SUBTRACT_ATI          Arg0 * Arg2 - Arg1

    where Arg0, Arg1 and Arg2 are derived from

        PRIMARY_COLOR_ARB       primary color of incoming fragment
        TEXTURE                 texture color of corresponding texture unit
        CONSTANT_ARB            texture environment constant color
        PREVIOUS_ARB            result of previous texture environment; on
                                texture unit 0, this maps to PRIMARY_COLOR_ARB

    In addition, the result may be scaled by 1.0, 2.0 or 4.0.

    Note that in addition to providing more flexible equations new source 
    inputs have been added for zero and one.

Issues

    None

New Procedures and Functions

    None

New Tokens

    Accepted by the <params> parameter of TexEnvf, TexEnvi, TexEnvfv,
    and TexEnviv when the <pname> parameter value is COMBINE_RGB_ARB
    or COMBINE_ALPHA_ARB

        MODULATE_ADD_ATI                   0x8744
        MODULATE_SIGNED_ADD_ATI            0x8745
        MODULATE_SUBTRACT_ATI              0x8746


    Accepted by the <params> parameter of TexEnvf, TexEnvi, TexEnvfv,
    and TexEnviv when the <pname> parameter value is SOURCE0_RGB_ARB,
    SOURCE1_RGB_ARB, SOURCE2_RGB_ARB, SOURCE0_ALPHA_ARB,
    SOURCE1_ALPHA_ARB, or SOURCE2_ALPHA_ARB

        ZERO
        ONE

Additions to Chapter 2 of the OpenGL 1.2 Specification (OpenGL Operation)

    None

Additions to Chapter 3 of the OpenGL 1.2 Specification (Rasterization)

    Added to subsection 3.8.9, before the paragraph describing the
    state requirements:

    If the value of TEXTURE_ENV_MODE is COMBINE_ARB, the form of the
    texture function depends on the values of COMBINE_RGB_ARB and
    COMBINE_ALPHA_ARB, according to table 3.20. The RGB and ALPHA
    results of the texture function are then multiplied by the values
    of RGB_SCALE_ARB and ALPHA_SCALE, respectively. The results are
    clamped to [0,1].

        COMBINE_RGB_ARB         Texture Function
        ------------------      ----------------
        REPLACE                 Arg0
        MODULATE                Arg0 * Arg1
        ADD                     Arg0 + Arg1
        SIGNED_ADD_ARB          Arg0 + Arg1 - 0.5
        INTERPOLATE_ARB         Arg0 * (Arg2) + Arg1 * (1-Arg2)
        SUBTRACT_ARB            Arg0 - Arg1
        MODULATE_ADD_ATI        Arg0 * Arg2 + Arg1
        MODULATE_SIGNED_ADD_ATI Arg0 * Arg2 + Arg1 - 0.5
        MODULATE_SUBTRACT_ATI   Arg0 * Arg2 - Arg1


        COMBINE_ALPHA_ARB       Texture Function
        ------------------      ----------------
        REPLACE                 Arg0
        MODULATE                Arg0 * Arg1
        ADD                     Arg0 + Arg1
        SIGNED_ADD_ARB          Arg0 + Arg1 - 0.5
        INTERPOLATE_ARB         Arg0 * (Arg2) + Arg1 * (1-Arg2)
        SUBTRACT_ARB            Arg0 - Arg1
        MODULATE_ADD_ATI        Arg0 * Arg2 + Arg1
        MODULATE_SIGNED_ADD_ATI Arg0 * Arg2 + Arg1 - 0.5
        MODULATE_SUBTRACT_ATI   Arg0 * Arg2 - Arg1

    The arguments Arg0, Arg1 and Arg2 are determined by the values of
    SOURCE<n>_RGB_ARB, SOURCE<n>_ALPHA_ARB, OPERAND<n>_RGB_ARB and
    OPERAND<n>_ALPHA_ARB. In the following two tables, Ct and At are
    the filtered texture RGB and alpha values; Cc and Ac are the 
    texture environment RGB and alpha values; Cf and Af are the RGB 
    and alpha of the primary color of the incoming fragment; and Cp 
    and Ap are the RGB and alpha values resulting from the previous 
    texture environment. On texture environment 0, Cp and Ap are 
    identical to Cf and Af, respectively. The relationship is 
    described in tables 3.21 and 3.22.

        SOURCE<n>_RGB_ARB       OPERAND<n>_RGB_ARB      Argument
        -----------------       --------------          --------
        TEXTURE                 SRC_COLOR               Ct
                                ONE_MINUS_SRC_COLOR     (1-Ct)
                                SRC_ALPHA               At
                                ONE_MINUS_SRC_ALPHA     (1-At)
        CONSTANT_ARB            SRC_COLOR               Cc
                                ONE_MINUS_SRC_COLOR     (1-Cc)
                                SRC_ALPHA               Ac
                                ONE_MINUS_SRC_ALPHA     (1-Ac)
        PRIMARY_COLOR_ARB       SRC_COLOR               Cf
                                ONE_MINUS_SRC_COLOR     (1-Cf)
                                SRC_ALPHA               Af
                                ONE_MINUS_SRC_ALPHA     (1-Af)
        PREVIOUS_ARB            SRC_COLOR               Cp
                                ONE_MINUS_SRC_COLOR     (1-Cp)
                                SRC_ALPHA               Ap
                                ONE_MINUS_SRC_ALPHA     (1-Ap)
        ZERO                    SRC_COLOR               0
                                ONE_MINUS_SRC_COLOR     1
                                SRC_ALPHA               0
                                ONE_MINUS_SRC_ALPHA     1
        ONE                     SRC_COLOR               1
                                ONE_MINUS_SRC_COLOR     0
                                SRC_ALPHA               1
                                ONE_MINUS_SRC_ALPHA     0


        Table 3.21: Arguments for COMBINE_RGB_ARB functions

        SOURCE<n>_ALPHA_ARB     OPERAND<n>_ALPHA_ARB    Argument
        -----------------       --------------          --------
        TEXTURE                 SRC_ALPHA               At
                                ONE_MINUS_SRC_ALPHA     (1-At)
        CONSTANT_ARB            SRC_ALPHA               Ac
                                ONE_MINUS_SRC_ALPHA     (1-Ac)
        PRIMARY_COLOR_ARB       SRC_ALPHA               Af
                                ONE_MINUS_SRC_ALPHA     (1-Af)
        PREVIOUS_ARB            SRC_ALPHA               Ap
                                ONE_MINUS_SRC_ALPHA     (1-Ap)
        ZERO                    SRC_ALPHA               0
                                ONE_MINUS_SRC_ALPHA     1
        ONE                     SRC_ALPHA               1
                                ONE_MINUS_SRC_ALPHA     0

        Table 3.22: Arguments for COMBINE_ALPHA_ARB functions



Additions to Chapter 4 of the OpenGL 1.2 Specification (Per-Fragment Operations
and the Framebuffer)

    None

Additions to Chapter 5 of the OpenGL 1.2 Specification (Special Functions)

    None

Additions to Chapter 6 of the OpenGL 1.2 Specification (State and State Requests)

    None

New State

    None

New Implementation Dependent State

    None

Revision History

   Date: 8/02/2002
   Revision: 1.01
      - Changed constant MODULATE_ADD_SIGNED_ATI to MODULATE_SIGNED_ADD_ATI.

   Date: 8/01/2002
   Revision: 1.0
      - First release based on ATIX version.
