ANR AI Matte Propagator

Overview

AI Matte Propagator takes a matte you made on one frame, the Init Frame, and follows the subject with it through the shot, forward and backward from that frame. The matte can come from anything: a roto, a paint stroke, a key, or a frame of ANR Matte Creator.

Nothing runs until you press Start Propagation. The node then reads your mask on the Init Frame and the plate around it, and every frame you play or render gets its own matte.

The result is the raw propagated matte: soft (Raw Soft) or cut to black and white (Raw Hard). To refine hair and soft edges afterwards, follow it with ANR AI Matte Perfector.

Inputs

1. Sourcerequired

   The plate the subject moves in. The AI follows the subject through its pictures.

2. Maskrequired

   Your matte (its alpha). Only the Init Frame is read, so it only needs to be right on that frame.

Output. The Source with the propagated matte in alpha. Display sets the RGB: the picture tinted with the matte (Matte Overlay, the default), the matte in black and white, the picture premultiplied, or the picture untouched.

Quick start

1. Draw your matte on one frame with a Roto (or any matte) and connect it to Mask. Connect the plate to Source.
2. Go to that frame and press Set to Current Frame, or type it into Init Frame.
3. Press Start Propagation. The Status line confirms the frame it started from.
4. Play or render the shot. Check the matte with Display on Matte Overlay.
5. For the comp, set Display to Straight (RGB + alpha) or Premultiplied, or take the alpha from the node.

The panel

The node's panel as Nuke shows it, with the values of a new node. Click any control to see what it does; tabs and sections work as in Nuke.

All controls

Tips

• Choose an Init Frame where the subject is fully in view and clearly separated from the background: the AI starts from exactly what you painted there.
• On large plates, raise Processing Resolution to 2560 or 3840 to keep more edge detail; it uses more graphics memory and time.
• Output > Raw Hard gives a clean black-and-white matte for garbage mattes and holdouts; Raw Soft keeps the AI model's soft transitions.
• Connect the result to ANR AI Matte Perfector's Mask input to rebuild hair and motion blur at full resolution.

Good to know

• Changing Init Frame, Processing Resolution or either input stops the propagation: press Start Propagation again.
• Start Propagation refuses when the Mask is empty on the Init Frame. Paint the matte first.
• The node needs an NVIDIA graphics card for practical speeds.
• If the Masking models were not installed with ANR Tools, Nuke offers to download them the first time you add the node in a session (Download models or Not now). After the download, press Start Propagation again.
• After about ten minutes without work (sooner when the graphics card is nearly full), the node gives its graphics memory back. The next frame loads the model again, which takes a moment.
• This node does not bake to disk. To freeze the result, render it out with a Write node, or follow it with ANR AI Matte Perfector and bake there.

Works with

ANR Matte CreatorDraw a box, click a point or type a word on one frame, and the AI model mattes that subject through the whole shot, with clean hair and soft edges.ANR AI Matte PerfectorGive it a rough or hard matte and the plate, and an AI matting model rebuilds the edge: hair, fur, motion blur and fine detail.ANR Edge Detail ExtensionRemoves the old background from the soft edges of a cut-out, hair and motion blur included, so it sits cleanly over a new background.