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  • Chunny Baker

Pre-Alpha Nuking

Some notes on Pre-multiplied Alpha and Nuke so far.

With digital images broken into individual components, RGBA

RGB- specifies how much color contributes to scene Alpha at base generally has no value, but can often be used to represent transparency

Alpha can be calculated in two ways

Conventional- Where RGB Specifies the color and A specifies how solid the color is.

Premultplied calculates the Rgb as how much color the object is adding to the scene. where the A determines how much it obscures whats behind it.

Why multiplied alpha?

in short using pre-multiplied alpha works more effectively for alpha cutouts. It works better as it is a super set of conventional and additive blending.

important for texture filtering, often when we are texture filtering Post multiplied or conventional blending distorts and muddies co lours.

A*rgb apha has been pre-multiplied by color

unpremult> divides rgb by a

Premult multiplies

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