glblendequation(3g) [osx man page]
GLBLENDEQUATION(3G) GLBLENDEQUATION(3G) NAME
glBlendEquation - set the blend equation C SPECIFICATION
void glBlendEquation( GLenum mode ) PARAMETERS
mode specifies how source and destination colors are combined. It must be GL_FUNC_ADD, GL_FUNC_SUBTRACT, GL_FUNC_REVERSE_SUBTRACT, GL_MIN, GL_MAX. DESCRIPTION
The blend equation determines how a new pixel (the ``source'' color) is combined with a pixel already in the framebuffer (the ``destina- tion'' color). GL_MIN sets the blend equation so that each component of the result color is the minimum of the corresponding components of the source and destination colors. GL_MAX sets the blend equation so that each component of the result color is the maximum of the corresponding components of the source and destination colors. The remaining blend equations use the source and destination blend factors specified by glBlendFunc. See glBlendFunc for a description of the various blend factors. In the equations that follow, source and destination color components are referred to as (Rs, Gs, Bs, As ) and (Rd, Gd, Bd, Ad ), respec- tively. The result color is referred to as (Rr, Gr, Br, Ar ). The source and destination blend factors are denoted (sR, sG, sB, sA ) and (dR, dG, dB, dA ), respectively. For these equations all color components are understood to have values in the range [0, 1]. GL_FUNC_ADD sets the blend equation so that the source and destination data are added. Each component of the source color is multiplied by the corresponding source factor, then each component of the destination color is multiplied by the corresponding destination factor. The result is the componentwise sum of the two products, clamped to the range [0, 1]. Rr = min (1, Rs sR + Rd dR ) Gr = min (1, Gs sG + Gd dG ) Br = min (1, Bs sB + Bd dB ) Ar = min (1, As sA + Ad dA ) GL_FUNC_SUBTRACT Is like GL_FUNC_ADD except the product of the destination factor and the destination color is componentwise subtracted from the product of the source factor and the source color. The result is clamped to the range [0, 1]. Rr = max (0 , Rs sR - Rd dR ) Gr = max (0 , Gs sG - Gd dG ) Br = max (0 , Bs sB - Bd dB ) Ar = max (0 , As sA - Ad dA ) GL_FUNC_REVERSE_SUBTRACT Is like GL_FUNC_ADD except the product of the source factor and the source color is componentwise subtracted from the product of the destination factor and the destination color. The result is clamped to the range [0, 1]. Rr = max (0 , Rd dR - Rs sR ) Gr = max (0 , Gd dG - Gs sG ) Br = max (0 , Bd dB - Bs sB ) Ar = max (0 , Ad dA - As sA ) The GL_MIN and GL_MAX equations are useful for applications that analyze image data (image thresholding against a constant color, for example). The GL_FUNC_ADD equation is useful for antialiasing and trans- parency, among other things. Initially, the blend equation is set to GL_FUNC_ADD. NOTES
glBlendEquation is part of the GL_ARB_imaging subset. glBlendEquation is present only if GL_ARB_imaging is returned when glGetString is called with GL_EXTENSIONS as its argument. The GL_MIN, and GL_MAX equations do not use the source or destination factors, only the source and destination colors. ERRORS
GL_INVALID_ENUM is generated if mode is not one of GL_FUNC_ADD, GL_FUNC_SUBTRACT, GL_FUNC_REVERSE_SUBTRACT, GL_MAX, or GL_MIN. GL_INVALID_OPERATION is generated if glBlendEquation is executed between the execution of glBegin and the corresponding execution of glEnd. ASSOCIATED GETS
glGet with an argument of GL_BLEND_EQUATION SEE ALSO
glGetString, glBlendColor, glBlendFunc GLBLENDEQUATION(3G)
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GLBLENDEQUATIONSEPAR(3G) [FIXME: manual] GLBLENDEQUATIONSEPAR(3G) NAME
glBlendEquationSeparate - set the RGB blend equation and the alpha blend equation separately C SPECIFICATION
void glBlendEquationSeparate(GLenum modeRGB, GLenum modeAlpha); void glBlendEquationSeparatei(GLuint buf, GLenum modeRGB, GLenum modeAlpha); PARAMETERS
buf for glBlendEquationSeparatei, specifies the index of the draw buffer for which to set the blend equations. modeRGB specifies the RGB blend equation, how the red, green, and blue components of the source and destination colors are combined. It must be GL_FUNC_ADD, GL_FUNC_SUBTRACT, GL_FUNC_REVERSE_SUBTRACT, GL_MIN, GL_MAX. modeAlpha specifies the alpha blend equation, how the alpha component of the source and destination colors are combined. It must be GL_FUNC_ADD, GL_FUNC_SUBTRACT, GL_FUNC_REVERSE_SUBTRACT, GL_MIN, GL_MAX. DESCRIPTION
The blend equations determines how a new pixel (the ''source'' color) is combined with a pixel already in the framebuffer (the ''destination'' color). These functions specifie one blend equation for the RGB-color components and one blend equation for the alpha component. glBlendEquationSeparatei specifies the blend equations for a single draw buffer whereas glBlendEquationSeparate sets the blend equations for all draw buffers. The blend equations use the source and destination blend factors specified by either glBlendFunc() or glBlendFuncSeparate(). See glBlendFunc() or glBlendFuncSeparate() for a description of the various blend factors. In the equations that follow, source and destination color components are referred to as R s G s B s A s and R d G d B d A d, respectively. The result color is referred to as R r G r B r A r. The source and destination blend factors are denoted s R s G s B s A and d R d G d B d A, respectively. For these equations all color components are understood to have values in the range 0 1. +-----------------------------+-----------------------------------------------------+-----------------------------------------------------+ | | | | | Mode | RGB | Alpha | | | Components | Component | | | | | +-----------------------------+-----------------------------------------------------+-----------------------------------------------------+ |GL_FUNC_ADD | <div> | <div> | | | | | | | | | | | Rr | Ar | | | = | = | | | | | | | R | A | | | s | s | | | | | | | | | | | s | s | | | R | A | | | | | | | + | + | | | R | A | | | d | d | | | | | | | | | | | d | d | | | R | A | | | | | | | | | | | | | | | </div> | </div> | | | <div> | | | | | | | | | | | | Gr | | | | = | | | | | | | | G | | | | s | | | | | | | | | | | | s | | | | G | | | | | | | | + | | | | G | | | | d | | | | | | | | | | | | d | | | | G | | | | | | | | | | | | | | | | </div> | | | | <div> | | | | | | | | | | | | Br | | | | = | | | | | | | | B | | | | s | | | | | | | | | | | | s | | | | B | | | | | | | | + | | | | B | | | | d | | | | | | | | | | | | d | | | | B | | | | | | | | | | | | | | | | </div> | | +-----------------------------+-----------------------------------------------------+-----------------------------------------------------+ |GL_FUNC_SUBTRACT | <div> | <div> | | | | | | | | | | | Rr | Ar | | | = | = | | | | | | | R | A | | | s | s | | | | | | | | | | | s | s | | | R | A | | | | | | | - | - | | | R | A | | | d | d | | | | | | | | | | | d | d | | | R | A | | | | | | | | | | | | | | | </div> | </div> | | | <div> | | | | | | | | | | | | Gr | | | | = | | | | | | | | G | | | | s | | | | | | | | | | | | s | | | | G | | | | | | | | - | | | | G | | | | d | | | | | | | | | | | | d | | | | G | | | | | | | | | | | | | | | | </div> | | | | <div> | | | | | | | | | | | | Br | | | | = | | | | | | | | B | | | | s | | | | | | | | | | | | s | | | | B | | | | | | | | - | | | | B | | | | d | | | | | | | | | | | | d | | | | B | | | | | | | | | | | | | | | | </div> | | +-----------------------------+-----------------------------------------------------+-----------------------------------------------------+ |GL_FUNC_REVERSE_SUBTRACT | <div> | <div> | | | | | | | | | | | Rr | Ar | | | = | = | | | | | | | R | A | | | d | d | | | | | | | | | | | d | d | | | R | A | | | | | | | - | - | | | R | A | | | s | s | | | | | | | | | | | s | s | | | R | A | | | | | | | | | | | | | | | </div> | </div> | | | <div> | | | | | | | | | | | | Gr | | | | = | | | | | | | | G | | | | d | | | | | | | | | | | | d | | | | G | | | | | | | | - | | | | G | | | | s | | | | | | | | | | | | s | | | | G | | | | | | | | | | | | | | | | </div> | | | | <div> | | | | | | | | | | | | Br | | | | = | | | | | | | | B | | | | d | | | | | | | | | | | | d | | | | B | | | | | | | | - | | | | B | | | | s | | | | | | | | | | | | s | | | | B | | | | | | | | | | | | | | | | </div> | | +-----------------------------+-----------------------------------------------------+-----------------------------------------------------+ |GL_MIN | <div> | <div> | | | | | | | | | | | Rr | Ar | | | = | = | | | | | | | min | min | | | | | | | | | | | | | | | R | A | | | s | s | | | | | | | | | | | | | | | R | A | | | d | d | | | | | | | | | | | | | | | | | | | | | | | </div> | </div> | | | <div> | | | | | | | | | | | | Gr | | | | = | | | | | | | | min | | | | | | | | | | | | | | | | G | | | | s | | | | | | | | | | | | | | | | G | | | | d | | | | | | | | | | | | | | | | | | | | | | | | </div> | | | | <div> | | | | | | | | | | | | Br | | | | = | | | | | | | | min | | | | | | | | | | | | | | | | B | | | | s | | | | | | | | | | | | | | | | B | | | | d | | | | | | | | | | | | | | | | | | | | | | | | </div> | | +-----------------------------+-----------------------------------------------------+-----------------------------------------------------+ |GL_MAX | <div> | <div> | | | | | | | | | | | Rr | Ar | | | = | = | | | | | | | max | max | | | | | | | | | | | | | | | R | A | | | s | s | | | | | | | | | | | | | | | R | A | | | d | d | | | | | | | | | | | | | | | | | | | | | | | </div> | </div> | | | <div> | | | | | | | | | | | | Gr | | | | = | | | | | | | | max | | | | | | | | | | | | | | | | G | | | | s | | | | | | | | | | | | | | | | G | | | | d | | | | | | | | | | | | | | | | | | | | | | | | </div> | | | | <div> | | | | | | | | | | | | Br | | | | = | | | | | | | | max | | | | | | | | | | | | | | | | B | | | | s | | | | | | | | | | | | | | | | B | | | | d | | | | | | | | | | | | | | | | | | | | | | | | </div> | | +-----------------------------+-----------------------------------------------------+-----------------------------------------------------+ The results of these equations are clamped to the range 0 1. The GL_MIN and GL_MAX equations are useful for applications that analyze image data (image thresholding against a constant color, for example). The GL_FUNC_ADD equation is useful for antialiasing and transparency, among other things. Initially, both the RGB blend equation and the alpha blend equation are set to GL_FUNC_ADD. NOTES
The GL_MIN, and GL_MAX equations do not use the source or destination factors, only the source and destination colors. ERRORS
GL_INVALID_ENUM is generated if either modeRGB or modeAlpha is not one of GL_FUNC_ADD, GL_FUNC_SUBTRACT, GL_FUNC_REVERSE_SUBTRACT, GL_MAX, or GL_MIN. GL_INVALID_VALUE is generated by glBlendEquationSeparatei if buf is greater than or equal to the value of GL_MAX_DRAW_BUFFERS. ASSOCIATED GETS
glGet() with an argument of GL_BLEND_EQUATION_RGB glGet() with an argument of GL_BLEND_EQUATION_ALPHA SEE ALSO
glGetString(), glBlendColor(), glBlendFunc(), glBlendFuncSeparate() COPYRIGHT
Copyright (C) 2006 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/. [FIXME: source] 05/30/2012 GLBLENDEQUATIONSEPAR(3G)