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    $Date: 1995/03/31 04:40:34 $ $Revision: 1.3 $  
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homeprevnext Dependencies
homeprevnext Overview
    Blending capability is extended by respecifying the entire blend  
    equation.  While this document defines only two new equations, the  
    BlendEquationEXT procedure that it defines will be used by subsequent  
    extensions to define additional blending equations.  
    The two new equations defined by this extension produce the minimum  
    (or maximum) color components of the source and destination colors.  
    Taking the maximum is useful for applications such as maximum projection  
    in medical imaging.  
homeprevnext Issues
    *   I've prefixed the ADD token with FUNC, to indicate that the blend  
        equation includes the parameters specified by BlendFunc.  (The min  
        and max equations don't.)  Is this necessary?  Is it too ugly?  
        Is there a better way to accomplish the same thing?  
homeprevnext New Procedures and Functions
    void BlendEquationEXT(enum mode);  
homeprevnext New Tokens
    Accepted by the <mode> parameter of BlendEquationEXT:  
        FUNC_ADD_EXT                     0x8006  
        MIN_EXT                          0x8007  
        MAX_EXT                          0x8008  
    Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,  
    GetFloatv, and GetDoublev:  
        BLEND_EQUATION_EXT               0x8009  
homeprevnext Additions to Chapter 2 of the GL Specification (OpenGL Operation)
homeprevnext Additions to Chapter 3 of the GL Specification (Rasterization)
homeprevnext Additions to Chapter 4 of the GL Specification (Per-Fragment Operations and the Framebuffer)
    The GL Specification defines a single blending equation.  This  
    extension introduces a blend equation mode that is specified by calling  
    BlendEquationEXT with one of three enumerated values.  The default  
    value FUNC_ADD_EXT specifies that the blending equation defined in  
    the GL Specification be used.  This equation is  
        C' = (Cs * S) + (Cd * D)  
             /  1.0     C' > 1.0  
        C = (  
             \   C'     C' <= 1.0  
    where Cs and Cd are the source and destination colors, and S and D are  
    as specified by BlendFunc.  
    If BlendEquationEXT is called with <mode> set to MIN_EXT, the  
    blending equation becomes  
        C = min (Cs, Cd)  
    Finally, if BlendEquationEXT is called with <mode> set to MAX_EXT, the  
    blending equation becomes  
        C = max (Cs, Cd)  
    In all cases the blending equation is evaluated separately for each  
    color component.  
homeprevnext Additions to Chapter 5 of the GL Specification (Special Functions)
homeprevnext Additions to Chapter 6 of the GL Specification (State and State Requests)
homeprevnext Additions to the GLX Specification
homeprevnext GLX Protocol
    A new GL rendering command is added. The following command is sent to the   
    server as part of a glXRender request:  
            2           8               rendering command length  
            2           4097            rendering command opcode  
            4           ENUM            mode  
homeprevnext Errors
    INVALID_ENUM is generated by BlendEquationEXT if its single parameter  
    is not FUNC_ADD_EXT, MIN_EXT, or MAX_EXT.  
    INVALID_OPERATION is generated if BlendEquationEXT is executed between  
    the execution of Begin and the corresponding execution to End.  
homeprevnext New State
    Get Value           Get Command     Type    Initial Value   Attribute  
    ---------           -----------     ----    -------------   ---------  
    BLEND_EQUATION_EXT  GetIntegerv     Z3      FUNC_ADD_EXT    color-buffer  
homeprevnext New Implementation Dependent State
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