GLBLENDEQUATION(3G) GLBLENDEQUATION(3G)

glBlendEquation - set the blend equation

void glBlendEquation( GLenum 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.
    

  










The blend equation determines how a new pixel (the ``source''
    color) is combined with a pixel already in the framebuffer (the
    ``destination'' color).



  

  
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.

  

  
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 ),
    respectively. 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].



  

  
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 )

  







  

  
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 )

  







  

  
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 transparency,
    among other things.


Initially, the blend equation is set to GL_FUNC_ADD.








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.








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.









  

  










glGetString, glBlendColor, glBlendFunc