ANR Edge Detail Extension

Overview

Every soft pixel of a cut-out, in hair, fur, motion blur or an antialiased edge, is a mix of the subject's colour and the background it was shot against. AI mattes also call some pixels solid that still carry background. Comped over a new background, that old colour shows as a fringe or a halo.

Edge Detail Extension solves each soft pixel back into its two parts, the subject's own colour and the original background, in a band round the edge. It replaces only the colour there and keeps the plate's own texture, so fine strands are not smeared into one flat colour. The inside of the matte stays exactly as it was.

It also carries the clean edge colour a little past the matte, so later blurs and filters do not pull black or old background into the edge. The node runs no AI model; it works on any matte, from a key, a roto or ANR Matte Creator.

Inputs

1. Sourcerequired

   The cut-out: premultiplied RGBA (the usual case), or the untouched picture with the matte in alpha (set Input Is to Straight (RGB + alpha)).

2. Plateoptional

   The original, uncut plate, lined up with the cut-out. When connected, the solve also sees the real background just outside the edge, which helps on thin hair.

3. Maskoptional

   Limits where the fix is applied (its alpha): outside the mask the input passes through.

Output. By default the fixed cut-out, premultiplied, ready to Merge over the new background. Output can also give the clean colour unpremultiplied with the matte in alpha, or the estimated original background.

Quick start

1. Make your cut-out as usual, for example ANR Matte Creator with Display set to Premultiplied.
2. Add ANR Edge Detail Extension and connect the cut-out to Source. If you have the original plate, connect it to Plate.
3. Merge the result over the new background and compare it with the old edge.
4. If a fringe remains just inside the edge, raise Edge Width or Colour From Inside.
5. If the edge looks blotchy, raise Smoothness; if it looks too flat, lower it.

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

• AI mattes tend to read a little wide or soft; Colour From Inside above 0.5 takes more of the edge colour from the solid core and hides the old background better.
• Output > Estimated Background shows what the node thinks the subject was shot against, which is a quick way to see what it is taking out of the edge.
• Use Output > Straight (clean colour + alpha) when you need to grade or filter the subject before premultiplying it yourself.
• Raise Quality to 4 for a stubborn edge; it costs speed.
• Mix compares the fix with the original edge; a Mask limits the fix to the problem area, such as the hair.

Good to know

• The node runs no AI model and needs no graphics card.
• Connect Plate only if it lines up exactly with the cut-out; a shifted plate puts the wrong background into the solve.
• Set Input Is to match what you connect: a straight picture read as premultiplied (or the reverse) gives wrong edge colours.

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 AI Matte PropagatorPaint or roto the matte on one frame, press Start Propagation, and the AI model carries that matte through the rest of the shot.ANR Edge ColorGives the soft edges of a keyed or rotoed element the colour of the background behind them, so they blend in, without touching the alpha.ANR Light WrapWraps the background's light softly around the edges of a keyed or CG element, so it sits in the plate instead of looking cut out.