The blending state combines
BlendEquation and BlendFunction and the
enabled flag to define the full blending state for combining source and
destination fragments when rendering.
This is a helper when using custom render states with Appearance#renderState.
成员(属性)
Blending is enabled using additive blending,
source(source.alpha) + destination.
Blending is enabled using alpha blending,
source(source.alpha) + destination(1 - source.alpha).
Blending is disabled.
Blending is enabled using alpha blending with premultiplied alpha,
source + destination(1 - source.alpha).