Signal Chain

A patch is the chain you build: modules run in the order shown top to bottom in Chain, each one blending its own output into the running composite before the next module runs. The last module in that order is what Output shows.

Module states are LIVE, BYP, and MUTE. BYP skips a module’s contribution. MUTE clears the chain at that module: subsequent modules receive an empty image, and its Sends are empty.

How a module’s output combines with what came before it is set by its own Blend Selector, with the same seven modes everywhere: Add, Multiply, Screen, Difference, XOR, Replace, and Phoenix. INSERT labels the first one Additive. FEEDBACK has a second selector, Loop Blend, for how the loop recombines with itself; see FEEDBACK.

Empty areas

The chain starts empty. A module that draws only part of the frame, such as SCOPE, SHAPE, TEXT or SPRITE, leaves the rest see-through, and it stays see-through for every module below until something draws there. The Output window, recordings and snapshots show empty areas as black; NDI, Spout and Syphon send them as transparency.

Add, Screen, Difference, XOR and Replace paint a module’s picture onto what is below it, so over an empty area the result is the module’s own picture. Multiply and Phoenix only change what is already there, so over an empty area they leave it empty.

Effects built for a whole picture see the chain over black: an INSERT’s Insert FX, SCOPE’s Insert FX, FEEDBACK’s Pre and Post Insert FX, and ISF filters. They behave exactly as on a black background, and wherever they draw nothing the area stays empty. An effect that lights an empty area, such as a Glow halo or Invert turning black to white, makes that area visible. A generator’s own Insert FX run on that module’s picture before it enters the chain, so they see its see-through areas.

Related: Insert FX Chains, AUX Sends and Buses.