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homeprevnext Name
homeprevnext Name Strings
homeprevnext Contact
    Mark J. Kilgard, NVIDIA Corporation (mjk 'at'  
homeprevnext Notice
    Copyright NVIDIA Corporation, 1999.  
homeprevnext Status
    Shipping (version 1.0)  
    NVIDIA, Mesa 3.1, and possibly ATI support this.  
    This extension's texture coordinate genreation functionality is  
    incoporated into the ARB_texture_cube_map extension.  The same  
    enumerant values are used.  
homeprevnext Version
    January 14, 2000  
    $Date$ $Revision$  
homeprevnext Number
homeprevnext Dependencies
    Written based on the wording of the OpenGL 1.2 specification but  
    not dependent on it.  
homeprevnext Overview
    This extension provides two new texture coordinate generation modes  
    that are useful texture-based lighting and environment mapping.  
    The reflection map mode generates texture coordinates (s,t,r)  
    matching the vertex's eye-space reflection vector.  The reflection  
    map mode is useful for environment mapping without the singularity  
    inherent in sphere mapping.  The normal map mode generates texture  
    coordinates (s,t,r) matching the vertex's transformed eye-space  
    normal.  The normal map mode is useful for sophisticated cube map  
    texturing-based diffuse lighting models.  
homeprevnext Issues
    Should we place the normal/reflection vector in the (s,t,r) texture  
    coordinates or (s,t,q) coordinates?  
      RESOLUTION:  (s,t,r).  Even if the proposed hardware uses "q" for  
      the third component, the API should claim to support generation of  
      (s,t,r) and let the texture matrix (through a concatenation with  
      the user-supplied texture matrix) move "r" into "q".  
    Should you be able to have some texture coordinates computing  
    REFLECTION_MAP_NV and others not?  Same question with NORMAL_MAP_NV.  
      RESOLUTION:  YES. This is the way that SPHERE_MAP works.  It is  
      not clear that this would ever be useful though.  
    Should something special be said about the handling of the q  
    texture coordinate for this spec?  
      RESOLUTION:  NO.  But the following paragraph is useful for  
      implementors concerned about the handling of q.  
      The REFLECTION_MAP_NV and NORMAL_MAP_NV modes are intended to supply  
      reflection and normal vectors for cube map texturing hardware.  
      When these modes are used for cube map texturing, the generated  
      texture coordinates can be thought of as a reflection vector.  
      The value of the q texture coordinate then simply scales the  
      vector but does not change its direction.  Because only the vector  
      direction (not the vector magnitude) matters for cube map texturing,  
      implementations are free to leave q undefined when any of the s,  
      t, or r texture coordinates are generated using REFLECTION_MAP_NV  
      or NORMAL_MAP_NV.  
homeprevnext New Procedures and Functions
homeprevnext New Tokens
    Accepted by the <param> parameters of TexGend, TexGenf, and TexGeni  
    when <pname> parameter is TEXTURE_GEN_MODE:  
        NORMAL_MAP_NV                      0x8511  
        REFLECTION_MAP_NV                  0x8512  
    When the <pname> parameter of TexGendv, TexGenfv, and TexGeniv is  
    TEXTURE_GEN_MODE, then the array <params> may also contain  
homeprevnext Additions to Chapter 2 of the 1.2 Specification (OpenGL Operation)
 --  Section 2.10.4 "Generating Texture Coordinates"  
      Change the last sentence in the 1st paragraph to:  
      "If <pname> is TEXTURE_GEN_MODE, then either <params> points to  
      or <param> is an integer that is one of the symbolic constants  
      Add these paragraphs after the 4th paragraph:  
      "If TEXTURE_GEN_MODE indicates REFLECTION_MAP_NV, compute the  
      reflection vector r as described for the SPHERE_MAP mode.  Then the  
      value assigned to an s coordinate (the first TexGen argument value  
      is S) is s = rx; the value assigned to a t coordinate is t = ry;  
      and the value assigned to a r coordinate is r = rz.  Calling TexGen  
      with a <coord> of Q when <pname> indicates REFLECTION_MAP_NV  
      generates the error INVALID_ENUM.  
      If TEXTURE_GEN_MODE indicates NORMAL_MAP_NV, compute the normal  
      vector n' as described in section 2.10.3.  Then the value assigned  
      to an s coordinate (the first TexGen argument value is S) is s =  
      nfx; the value assigned to a t coordinate is t = nfy; and the  
      value assigned to a r coordinate is r = nfz.  (The values nfx, nfy,  
      and nfz are the components of nf.)  Calling TexGen with a <coord>  
      of Q when <pname> indicates REFLECTION_MAP_NV generates the error  
      The last paragraph's first sentence should be changed to:  
      "The state required for texture coordinate generation comprises a  
      five-valued integer for each coordinate indicating coordinate  
      generation mode, ..."  
homeprevnext Additions to Chapter 3 of the 1.2 Specification (Rasterization)
homeprevnext Additions to Chapter 4 of the 1.2 Specification (Per-Fragment Operations and the Frame Buffer)
homeprevnext Additions to Chapter 5 of the 1.2 Specification (Special Functions)
homeprevnext Additions to Chapter 6 of the 1.2 Specification (State and State Requests)
homeprevnext Additions to the GLX Specification
homeprevnext Errors
     INVALID_ENUM is generated when TexGen is called with a <coord> of Q  
     when <pname> indicates REFLECTION_MAP_NV or NORMAL_MAP_NV.  
homeprevnext New State
(table 6.14, p204) change the entry for TEXTURE_GEN_MODE to:  
    Get Value            Type    Get Command     Initial Value   Description        Sec    Attribute  
    ---------            ----    -----------     -------------   -----------        ------ ---------  
    TEXTURE_GEN_MODE     4xZ5    GetTexGeniv    EYE_LINEAR      Function used for  2.10.4 texture  
                                                                 texgen (for s,t,r,  
                                                                 and q)  
(the type changes from 4xZ3 to 4xZ5)  
New Implementation State  
homeprevnext Revision History
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