1991-2006 Silicon Graphics, Inc.
glBlendEquationSeparate 3G
glBlendEquationSeparate set the RGB blend equation and the alpha blend equation separately

## C Specification

void `glBlendEquationSeparate` GLenum modeRGB GLenum modeAlpha

## Parameters

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`, or `GL_FUNC_REVERSE_SUBTRACT`.

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`, or `GL_FUNC_REVERSE_SUBTRACT`.

## Description

The blend equations determines how a new pixel (the ''source'' color) is combined with a pixel already in the framebuffer (the ''destination'' color). This function specifies one blend equation for the RGB-color components and one blend equation for the alpha component.

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 Components | Alpha Component
--- | --- | ---
`GL_FUNC_ADD` | Rr = R s ⁢ s R + R d ⁢ d R Gr = G s ⁢ s G + G d ⁢ d G Br = B s ⁢ s B + B d ⁢ d B | Ar = A s ⁢ s A + A d ⁢ d A
`GL_FUNC_SUBTRACT` | Rr = R s ⁢ s R - R d ⁢ d R Gr = G s ⁢ s G - G d ⁢ d G Br = B s ⁢ s B - B d ⁢ d B | Ar = A s ⁢ s A - A d ⁢ d A
`GL_FUNC_REVERSE_SUBTRACT` | Rr = R d ⁢ d R - R s ⁢ s R Gr = G d ⁢ d G - G s ⁢ s G Br = B d ⁢ d B - B s ⁢ s B | Ar = A d ⁢ d A - A s ⁢ s A

The results of these equations are clamped to the range 0 1 .

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`.

## Errors

`GL_INVALID_ENUM` is generated if either modeRGB or modeAlpha is not one of `GL_FUNC_ADD`, `GL_FUNC_SUBTRACT`, or `GL_FUNC_REVERSE_SUBTRACT`.

## Associated Gets

glGet with an argument of `GL_BLEND_EQUATION_RGB`

glGet with an argument of `GL_BLEND_EQUATION_ALPHA`

## See Also

glGetString, glBlendColor, glBlendEquation, glBlendFunc, glBlendFuncSeparate

## Copyright

Copyright 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/.