The blending state is optional and is not required if rasterization is disabled or when there are no color attachments in a subpass, in which a given graphics pipeline is used.
The blending state is used mainly to define the parameters of a blending operation. But it also serves other purposes. In it we specify a color mask which selects which color components are updated (written to) during rendering. It also controls the state of a logical operation. When enabled, one of the specified logical operations is performed between a fragment's color and a color already written in a framebuffer.
A logical operation is performed only for attachments with integer and normalized integer formats.
Supported logical operations include: ...
