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    SGI Date: 1997/02/26 03:36:30  SGI Revision: 1.6  
    $Id: //sw/main/docs/OpenGL/specs/GL_SGIS_generate_mipmap.txt#2 $  
homeprevnext Number
homeprevnext Dependencies
    EXT_texture is required  
    EXT_texture3D affects the definition of this extension  
    EXT_texture_object affects the definition of this extension  
    SGIS_texture_lod affects the definition of this extension  
homeprevnext Overview
    This extension defines a mechanism by which OpenGL can derive the  
    entire set of mipmap arrays when provided with only the base level  
    array.  Automatic mipmap generation is particularly useful when  
    texture images are being provided as a video stream.  
homeprevnext Issues
    *   How are edges handled?  
homeprevnext New Procedures and Functions
homeprevnext New Tokens
    Accepted by the <pname> parameter of TexParameteri, TexParameterf,  
    TexParameteriv, TexParameterfv, GetTexParameteriv, and GetTexParameterfv:  
        GENERATE_MIPMAP_SGIS            0x8191  
    Accepted by the <target> parameter of Hint, and by the <pname>  
    parameter of GetBooleanv, GetIntegerv, GetFloatv, and GetDoublev:  
        GENERATE_MIPMAP_HINT_SGIS       0x8192  
homeprevnext Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)
homeprevnext Additions to Chapter 3 of the 1.0 Specification (Rasterization)
    GL Specification Table 3.7 is updated as follows:  
        Name                            Type        Legal Values  
        ----                            ----        ------------  
        TEXTURE_WRAP_S                  integer     CLAMP, REPEAT  
        TEXTURE_WRAP_T                  integer     CLAMP, REPEAT  
        TEXTURE_WRAP_R_EXT              integer     CLAMP, REPEAT  
        TEXTURE_MIN_FILTER              integer     NEAREST, LINEAR,  
        TEXTURE_MAG_FILTER              integer     NEAREST, LINEAR,  
        TEXTURE_BORDER_COLOR            4 floats    any 4 values in [0,1]  
        DETAIL_TEXTURE_LEVEL_SGIS       integer     any non-negative integer  
        DETAIL_TEXTURE_MODE_SGIS        integer     ADD, MODULATE  
        TEXTURE_MIN_LOD_SGIS            float       any value  
        TEXTURE_MAX_LOD_SGIS            float       any value  
        TEXTURE_BASE_LEVEL_SGIS         integer     any non-negative integer  
        TEXTURE_MAX_LEVEL_SGIS          integer     any non-negative integer  
        GENERATE_MIPMAP_SGIS            boolean     TRUE or FALSE  
        Table 3.7: Texture parameters and their values.  
    This extension introduces a side effect to the modification of the  
    base level mipmap array.  The side effect is enabled on a per-texture  
    basis by calling TexParameteri, TexParameterf, TexParameteriv, or  
    TexParameterfv with <target> set to TEXTURE_1D, TEXTURE_2D, or  
    TEXTURE_3D_EXT, <pname> set to GENERATE_MIPMAP_SGIS, and <param>  
    set to TRUE (or <params> pointing to TRUE).  It is disabled using the  
    same call, with <param> set to FALSE, or <params> pointing to FALSE.  
    If SGIS_texture_lod is supported, the base level array is the array  
    number TEXTURE_BASE_LEVEL_SGIS.  Otherwise the base level array is  
    array zero.  
    If GENERATE_MIPMAP_SGIS is enabled, the side effect occurs whenever  
    any change is made to the interior or edge image values of the base  
    level texture array.  The side effect is computation of a complete  
    set of mipmap arrays, all derived from the modified base level array.  
    Array levels BASE+1 through BASE+p are replaced with derived arrays,  
    regardless of their previous contents.  All other texture arrays,  
    including the base array, are left unchanged by this mipmap computation.  
    The internal formats and border widths of the derived mipmap arrays  
    all match those of the base array, and the dimensions of the derived  
    arrays follow the requirements described in the Mipmapping section of  
    the GL Specification.  The result is that the set of mipmap arrays is  
    complete as defined by the GL Specification.  The contents of the  
    derived image arrays are computed by repeated, filtered reduction of  
    the base level image array.  This specification does not require any  
    particular filter algorithm, though a simple 2x2 box filter is  
    recommended as the default filter.  Hint variable  
    GENERATE_MIPMAP_HINT_SGIS can be changed from its default value of  
    DONT_CARE to either FASTEST or NICEST, indicating to the implementation  
    that either the fastest or highest quality filter operation is desired.  
    These operations are not defined by this specification, however.  The  
    single hint value controls the filtering of all the textures, and is  
    evaluated when the filtering operation takes place.  
    Automatic mipmap generation is available for texture targets TEXTURE_1D,  
    TEXTURE_2D, and TEXTURE_3D_EXT only.  
homeprevnext Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations and the Frame Buffer)
homeprevnext Additions to Chapter 5 of the 1.0 Specification (Special Functions)
homeprevnext Additions to Chapter 6 of the 1.0 Specification (State and State Requests)
homeprevnext Additions to the GLX Specification
homeprevnext Dependencies on EXT_texture
    EXT_texture is required.  
homeprevnext Dependencies on EXT_texture3D
    If EXT_texture3D is not supported, references to 3D texture mapping and  
    to TEXTURE_3D_EXT in this document are invalid and should be ignored.  
homeprevnext Dependencies on EXT_texture_object
    If EXT_texture_object is implemented, the state value named  
    is added to the state vector of each texture object. When an attribute  
    set that includes texture information is popped, the bindings and  
    enables are first restored to their pushed values, then the bound  
    textures have their GENERATE_MIPMAP_SGIS parameters restored to their  
    pushed values.  
homeprevnext Dependencies on SGIS_texture_lod
    If SGIS_texture_lod is not supported, the base array level is always  
    level zero.  References in this document to TEXTURE_BASE_LEVEL_SGIS  
    should be ignored.  
homeprevnext Errors
homeprevnext New State
    Get Value                   Get Command       Type  Value     Attrib  
    ---------                   -----------       ----  -------   ------  
    GENERATE_MIPMAP_SGIS        GetTexParameteriv B     FALSE     texture  
    GENERATE_MIPMAP_HINT_SGIS   GetIntegerv       Z3    DONT_CARE hint  
homeprevnext New Implementation Dependent State
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