ANR Arc Branches

Overview

Arc Branches draws a jagged arc of light from a start point to an end point. The two ends stay where you put them; in between, the path wanders and writhes by itself as the shot plays. Side forks split off the main arc, and a glow surrounds the bright core.

Use it for lightning, electricity jumping between two objects, energy beams, magic and title effects. Positions are fractions of the frame: 0, 0 is the bottom-left corner and 1, 1 the top right. The arc is drawn over Source, or alone on transparency when nothing is connected there.

Connect a matte to Obstacle and the main arc is pushed away from it, so a bolt can curve around a character or a logo.

Inputs

1. Sourceoptional

   The plate the arc is drawn over. Leave it empty to render the arc alone on transparency and merge it yourself.

2. Obstacleoptional

   A matte the main arc steers away from, such as an actor or a logo the bolt should go around. The node reads its alpha.

3. Maskoptional

   Limits where the arc appears: where the mask's alpha is black, Source shows unchanged.

Output. The arc, its forks and glow over Source, or alone on transparency, with an alpha. In float, the core keeps values above 1.

Quick start

1. Add ANR Arc Branches. Connect your plate to Source, or leave it empty to render the arc on its own.
2. Set Start X, Start Y, End X and End Y to the two points the arc joins.
3. Set Wander for how far the path strays from a straight line, and Forks for the number of side branches.
4. Set the look with Core Width, Glow Radius, Intensity and Color.
5. Play the shot: the arc moves by itself. Raise Evolution Speed for a nervous crackle, lower it for a slow writhe, or set it to 0 to freeze the shape.
6. Change Seed for a different arc with the same settings.

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

• Key Seed with constant (stepped) keys to make the bolt jump to a new shape on chosen frames, like separate strikes.
• Key Intensity for flashes and flicker.
• The arc is pushed along the slope of the Obstacle alpha, so blur that matte: a hard edge only deflects the arc right at the border, and a path through the middle of a large solid shape is not moved. Raise Obstacle Avoidance for a stronger push.
• Add a glow after the node, for example ANR Glow, for a soft bloom around the bolt.
• To pass the arc behind something in the plate, connect an inverted matte of that object to Mask.
• Key the start and end points to keep the arc on moving objects.

Good to know

• Only the main arc steers around the Obstacle; forks can still cross it. The steering is a soft push, not a guaranteed miss.
• Nothing is simulated or cached: each frame depends only on its own frame number and inputs, so scrubbing, render order and farm renders all give the same frames.
• The output always covers the project format.

Works with

ANR GlowA soft, layered bloom around bright lights and highlights, with control over its size, spread and colour, and a matte input to choose which lights glow.ANR Lightning 3DBranching 3D lightning and electric arcs between points you place, seen through your camera, with glow, strikes and optional smoke, fire and sparks.ANR Interactive LightLights an element with footage of a fire, lightning or a screen, through its normals and depth, with shadows from its own shape or from smoke.