glBlendEquationSeparate

glBlendEquationSeparate: man4/glBlendEquationSeparate.xml

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 specify 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 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 GL_MIN Rr = min ⁡ R s R d Gr = min ⁡ G s G d Br = min ⁡ B s B d Ar = min ⁡ A s A d GL_MAX Rr = max ⁡ R s R d Gr = max ⁡ G s G d Br = max ⁡ B s B d Ar = max ⁡ A s A d 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.

The GL_MIN, and GL_MAX equations do not use the source or destination factors, only the source and destination colors.