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GL_ARB_texture_env_add
homeprevnext Name
  
    ARB_texture_env_add  
  
homeprevnext Name Strings
  
    GL_ARB_texture_env_add  
  
homeprevnext Notice
  
    Copyright OpenGL Architectural Review Board, 1999.  
  
homeprevnext Contact
  
    Michael Gold, NVIDIA (gold 'at' nvidia.com)  
    Tom Frisinger, ATI (tfrisinger 'at' atitech.com)  
  
homeprevnext Status
  
    Complete. Approved by ARB on 12/8/1999  
  
homeprevnext Version
  
    Last Modified Date: June 22, 2000  
    Author Revision: 0.3  
  
    Based on:  EXT_texture_env_add  
               Date: 1999/03/22 Revision: 1.1  
  
homeprevnext Number
  
    ARB Extension #6  
  
homeprevnext Dependencies
  
    None  
  
homeprevnext Overview
  
    New texture environment function ADD is supported with the following  
    equation:  
                        Cv = min(1, Cf + Ct)  
  
    New function may be specified by calling TexEnv with ADD token.  
  
    One possible application is to add a specular highlight texture to  
    a Gouraud-shaded primitive to emulate Phong shading, in a single  
    pass.  
  
  
homeprevnext New Procedures and Functions
  
    None  
  
homeprevnext New Tokens
  
    Accepted by the <params> parameter of TexEnvf, TexEnvi, TexEnvfv, and  
    TexEnvfi when the <pname> parameter value is GL_TEXTURE_ENV_MODE  
  
        ADD  
  
homeprevnext Additions to Chapter 2 of the GL Specification (OpenGL Operation)
  
        None  
  
homeprevnext Additions to Chapter 3 of the GL Specification (Rasterization)
  
    The description of TEXTURE_ENV_MODE in the first paragraph of  
    section 3.8.9 should be modified as follows:  
  
    TEXTURE_ENV_MODE may be set to one of REPLACE, MODULATE, DECAL,  
    BLEND or ADD;  
  
    Table 3.19 is augmented as follows:  
  
            Base            DECAL      BLEND      ADD  
        Internal Format     tex func   tex func   tex func  
        ---------------     -----      -----      ---  
  
        ALPHA                ...        ...      Rv = Rf  
                             ...        ...      Gv = Gf  
                             ...        ...      Bv = Bf  
                             ...        ...      Av = AfAt  
  
        LUMINANCE            ...        ...      Rv = min(1, Rf+Lt)  
         (or 1)              ...        ...      Gv = min(1, Gf+Lt)  
                             ...        ...      Bv = min(1, Bf+Lt)  
                             ...        ...      Av = Af  
  
        LUMINANCE_ALPHA      ...        ...      Rv = min(1, Rf+Lt)  
         (or 2)              ...        ...      Gv = min(1, Gf+Lt)  
                             ...        ...      Bv = min(1, Bf+Lt)  
                             ...        ...      Av = AfAt  
  
        INTENSITY            ...        ...      Rv = min(1, Rf+It)  
                             ...        ...      Gv = min(1, Gf+It)  
                             ...        ...      Bv = min(1, Bf+It)  
                             ...        ...      Av = min(1, Af+It)  
  
        RGB                  ...        ...      Rv = min(1, Rf+Rt)  
        (or 3)               ...        ...      Gv = min(1, Gf+Gt)  
                             ...        ...      Bv = min(1, Bf+Bt)  
                             ...        ...      Av = Af  
  
        RGBA                 ...        ...      Rv = min(1, Rf+Rt)  
        (or 4)               ...        ...      Gv = min(1, Gf+Gt)  
                             ...        ...      Bv = min(1, Bf+Bt)  
                             ...        ...      Av = AfAt  
  
  
        Table 3.19: Decal, blend and add texture functions.  
  
  
homeprevnext Additions to Chapter 4 of the GL Specification (Per-Fragment Operations and the Framebuffer)
  
    None  
  
homeprevnext Additions to Chapter 5 of the GL Specification (Special Functions)
  
    None  
  
homeprevnext Additions to Chapter 6 of the GL Specification (State and State Requests)
  
    None  
  
homeprevnext Additions to the GLX / WGL / AGL Specifications
  
    None  
  
homeprevnext GLX Protocol
  
    None  
  
homeprevnext Errors
  
    None  
  
homeprevnext New State
  
    The Type of TEXTURE_ENV_MODE in Table F.2 should be changed to  
  
        1 * xZ5  
  
homeprevnext New Implementation Dependent State
  
    None  
  
homeprevnext Revision History
  
    11/09/1999  0.1  
        - First ARB draft based on the original EXT draft.  
  
    1/13/2000   0.2  
        - Added justification to the overview  
        - Updated to describe modifications to 1.2.1 specification  
        - Added changes to description of TEXTURE_ENV_MODE parameter  
          to TexEnv{if} and TexEnv{if}v  
        - Added change to TEXTURE_ENV_MODE type (Z4 -> Z5)  
  
    6/22/2000   0.3  
        - The addition should saturate to 1.  
        - The addition should saturate to 1.  
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