The source and destination blend factors are often needed to complete specification of a blend operation. In most cases, the blend factor for both RGB values (F(rgb)) and alpha values (F(a)) are similar to one another, but in some cases, such as MTLBlendFactorSourceAlphaSaturated, the blend factor is slightly different. Four blend factors (MTLBlendFactorBlendColor, MTLBlendFactorOneMinusBlendColor, MTLBlendFactorBlendAlpha, and MTLBlendFactorOneMinusBlendAlpha) refer to a constant blend color value that is set by the setBlendColor(red:green:blue:alpha:) method of MTLRenderCommandEncoder.
Blend factor of one minus source alpha. This option supports dual-source blending and reads from the second color output of the fragment function.
This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.