Blog Posts: tagged with TCL

Some nodes in Nuke, such as the Particle Emitter or your favourite Camera Shake gizmo, have a random seed knob. This allows you to create a different variation of a setup using the same parameters on a given node. When these setups are used throughout a sequence, we often want to change up the random seed value so every shot matches an approved look, but doesn't behave in exactly the same way.

When setting up a sequence template, you could expression link all random seed knobs to a NoOp-based control panel, but there is a better, more automated way to get a "random" value by default.

Using TCL expressions in Nuke can help us to evaluate mathematical operations, as well as link values together to create something new. However, an often forgotten feature in Nuke is the ability to add expressions to RotoShapes and Paint strokes (which are also splines under the hood).

Nuke's built-in "Tracker linking dialog" (pictured above), helps us to link individual vertices to various things in a Tracker node, and is doing so by automatically adding TCL expressions for us! However, what if we wanted to link things the other way around?

I've recently been thinking about processes I do all the time that could potentially be automated. I found that any time I created a ScanlineRender node, I always added the $gui expression to its samples knob. So, why not automate that? Here's my solution code for your menu.py first, explanation below):

I often find myself labelling nodes with descriptors, so it's clear what each node is doing. This usually involves a TCL snippet to return a value of a certain knob. This article is intended to serve as a reference, so we have a good cheat sheet to turn to when we might need to find a specific TCL snippet.