kc3-lang/angle/extensions/EXT_blend_minmax.txt

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• Author : Geoff Lang
  Date : 2014-02-12 11:33:51
  Hash : 496123fd
  Message : Implement EXT_blend_minmax. BUG=angle:555 Change-Id: I1ae6a9783e718d16ee08bda5463f11cd52ad0967 Reviewed-on: https://chromium-review.googlesource.com/186123 Tested-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org>

• extensions/EXT_blend_minmax.txt

• Name
  
      EXT_blend_minmax
  
  Name Strings
  
      GL_EXT_blend_minmax
  
  Version
  
      Last Modified Date: September 17, 2009
      Version:            1.5
  
  Number
  
      OpenGL Extension #37
      OpenGL ES Extension #65
  
  Dependencies
  
      There is an interaction with OpenGL ES.
  
  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.
  
  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?
      
  New Procedures and Functions
  
      void BlendEquationEXT(enum mode);
  
  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
  
  Additions to Chapter 2 of the GL Specification (OpenGL Operation)
  
      None
  
  Additions to Chapter 3 of the GL Specification (Rasterization)
  
      None
  
  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.
  
  Additions to Chapter 5 of the GL Specification (Special Functions)
  
      None
  
  Additions to Chapter 6 of the GL Specification (State and State Requests)
  
      None
  
  Additions to the GLX Specification
  
      None
  
  GLX Protocol
  
      A new GL rendering command is added. The following command is sent to the 
      server as part of a glXRender request:
  
          BlendEquationEXT
              2           8               rendering command length
              2           4097            rendering command opcode
              4           ENUM            mode
  
  Dependencies on OpenGL ES
  
      If the GL is OpenGL ES, only the new MIN_EXT and MAX_EXT blend equations
      are introduced by this extension.  BlendEquationOES, FUNC_ADD_OES, and
      BLEND_EQUATION_OES are introduced by the OES_blend_subtract extension,
      which is required for this extension to operate.  Alternatively,
      OpenGL ES 2.0 is required, which introduces BlendEquation, FUNC_ADD, and
      BLEND_EQUATION without the suffixes.
  
      MIN_EXT and MAX_EXT should be added to Table 4.blendeq described in the
      OES_blend_subtract extension specification, and Table 4.1 of the OpenGL
      ES 2.0 specification.
  
      Mentions of GetDoublev, Begin/End, and GLX in this extension specification
      can be ignored for OpenGL ES.  Also, BlendEquationEXT and FUNC_ADD_EXT
      instead have the OES suffix courtesy of OES_blend_subtract, or no suffix
      courtesy of core OpenGL ES 2.0.
  
  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.
  
  New State
  
      Get Value           Get Command     Type    Initial Value   Attribute
      ---------           -----------     ----    -------------   ---------
      BLEND_EQUATION_EXT  GetIntegerv     Z3      FUNC_ADD_EXT    color-buffer
  
  New Implementation Dependent State
  
      None
  
  Revision History
  
      Version 1.5, September 17, 2009 (Jon Leech) -
          Merge into OpenGL Registry version of the extension and assign
          OpenGL ES extension number.
      Version 1.4, May 19, 2009 (Benj Lipchak) -
          Adapted for OpenGL ES.
      Version 1.3, May 31, 1995 -
          Last SGI revision.