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165 строки
4.9 KiB
Plaintext
165 строки
4.9 KiB
Plaintext
Name
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EXT_blend_minmax
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Name Strings
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GL_EXT_blend_minmax
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Version
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Last Modified Date: September 17, 2009
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Version: 1.5
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Number
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OpenGL Extension #37
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OpenGL ES Extension #65
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Dependencies
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There is an interaction with OpenGL ES.
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Overview
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Blending capability is extended by respecifying the entire blend
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equation. While this document defines only two new equations, the
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BlendEquationEXT procedure that it defines will be used by subsequent
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extensions to define additional blending equations.
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The two new equations defined by this extension produce the minimum
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(or maximum) color components of the source and destination colors.
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Taking the maximum is useful for applications such as maximum projection
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in medical imaging.
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Issues
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* I've prefixed the ADD token with FUNC, to indicate that the blend
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equation includes the parameters specified by BlendFunc. (The min
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and max equations don't.) Is this necessary? Is it too ugly?
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Is there a better way to accomplish the same thing?
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New Procedures and Functions
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void BlendEquationEXT(enum mode);
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New Tokens
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Accepted by the <mode> parameter of BlendEquationEXT:
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FUNC_ADD_EXT 0x8006
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MIN_EXT 0x8007
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MAX_EXT 0x8008
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Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,
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GetFloatv, and GetDoublev:
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BLEND_EQUATION_EXT 0x8009
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Additions to Chapter 2 of the GL Specification (OpenGL Operation)
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None
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Additions to Chapter 3 of the GL Specification (Rasterization)
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None
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Additions to Chapter 4 of the GL Specification (Per-Fragment Operations
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and the Framebuffer)
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The GL Specification defines a single blending equation. This
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extension introduces a blend equation mode that is specified by calling
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BlendEquationEXT with one of three enumerated values. The default
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value FUNC_ADD_EXT specifies that the blending equation defined in
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the GL Specification be used. This equation is
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C' = (Cs * S) + (Cd * D)
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/ 1.0 C' > 1.0
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C = (
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\ C' C' <= 1.0
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where Cs and Cd are the source and destination colors, and S and D are
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as specified by BlendFunc.
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If BlendEquationEXT is called with <mode> set to MIN_EXT, the
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blending equation becomes
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C = min (Cs, Cd)
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Finally, if BlendEquationEXT is called with <mode> set to MAX_EXT, the
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blending equation becomes
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C = max (Cs, Cd)
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In all cases the blending equation is evaluated separately for each
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color component.
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Additions to Chapter 5 of the GL Specification (Special Functions)
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None
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Additions to Chapter 6 of the GL Specification (State and State Requests)
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None
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Additions to the GLX Specification
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None
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GLX Protocol
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A new GL rendering command is added. The following command is sent to the
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server as part of a glXRender request:
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BlendEquationEXT
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2 8 rendering command length
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2 4097 rendering command opcode
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4 ENUM mode
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Dependencies on OpenGL ES
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If the GL is OpenGL ES, only the new MIN_EXT and MAX_EXT blend equations
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are introduced by this extension. BlendEquationOES, FUNC_ADD_OES, and
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BLEND_EQUATION_OES are introduced by the OES_blend_subtract extension,
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which is required for this extension to operate. Alternatively,
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OpenGL ES 2.0 is required, which introduces BlendEquation, FUNC_ADD, and
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BLEND_EQUATION without the suffixes.
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MIN_EXT and MAX_EXT should be added to Table 4.blendeq described in the
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OES_blend_subtract extension specification, and Table 4.1 of the OpenGL
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ES 2.0 specification.
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Mentions of GetDoublev, Begin/End, and GLX in this extension specification
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can be ignored for OpenGL ES. Also, BlendEquationEXT and FUNC_ADD_EXT
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instead have the OES suffix courtesy of OES_blend_subtract, or no suffix
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courtesy of core OpenGL ES 2.0.
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Errors
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INVALID_ENUM is generated by BlendEquationEXT if its single parameter
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is not FUNC_ADD_EXT, MIN_EXT, or MAX_EXT.
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INVALID_OPERATION is generated if BlendEquationEXT is executed between
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the execution of Begin and the corresponding execution to End.
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New State
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Get Value Get Command Type Initial Value Attribute
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--------- ----------- ---- ------------- ---------
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BLEND_EQUATION_EXT GetIntegerv Z3 FUNC_ADD_EXT color-buffer
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New Implementation Dependent State
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None
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Revision History
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Version 1.5, September 17, 2009 (Jon Leech) -
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Merge into OpenGL Registry version of the extension and assign
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OpenGL ES extension number.
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Version 1.4, May 19, 2009 (Benj Lipchak) -
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Adapted for OpenGL ES.
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Version 1.3, May 31, 1995 -
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Last SGI revision.
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