specify the equation used for both the RGB blend equation and the Alpha blend equation
for glBlendEquationi , specifies the index of the draw buffer for which to set the blend equation.
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 equations determine how a new pixel (the ''source'' color) is combined with a pixel already in the framebuffer (the ''destination'' color). This function sets both the RGB blend equation and the alpha blend equation to a single equation. glBlendEquationi specifies the blend equation for a single draw buffer whereas glBlendEquation sets the blend equation for all draw buffers.
These 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 and , respectively. The result color is referred to as . The source and destination blend factors are denoted and , respectively. For these equations all color components are understood to have values in the range .
|Mode||RGB Components||Alpha Component|
The results of these equations are clamped to the range .
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 .
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 .
glGet with an argument of GL_BLEND_EQUATION_RGB
glGet with an argument of GL_BLEND_EQUATION_ALPHA
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