Compositing Bites - learning compositing one node at a time

In this new series on compositing we will look at the very basic techniques of compositing. How compositing works under the hood. So if you want to grow your compositing skills beyond simply pressing a bunch of buttons and hope that the result is worthwhile stick around.

I am going to work in Nuke, because it is very well suited for this “under the hood” way of working as it exposes a lot of technical info in its UI already. However, the concepts work the same in any other compositing package like Fusion, After Effects, Photoshop, Blender or Natron. Please refer to your manual for equivalent functions.

If you want to follow along you can download the Nuke Non-Commercial edition.

The Most Basic Building Blocks

Compositing is at its core just a bunch of simple math. Most nodes can be approximated by two simple nodes which I will be using to illustrate the concepts I’m going to talk about in coming videos.

• Expression
• MergeExpression

With these two nodes and a bunch of rather simple formulas you can build a complete composite including transforms, blurs, even converting HDR images from probes to Lat/Long images. Now of course, you would not want to do that in a production workflow as you might literally spend all day typing in math formulas. But to dissect what happens when you blur something or adjust the gamma it is a very helpful tool.

To make my life a little easier I’ll also introduce two more nodes later on, the Matrix Node and the Color Matrix Node. Theoretically you could get by with just using Expression and MergeExpression nodes, but using the Matrix nodes makes a lot of things much simpler to type.

For a list of available functions you can look at the Nuke manual.

Slice Tool

Typing in a bunch of expressions gets tiresome to watch quickly, which is why I am going to visualize the effects using a custom built Slice tool. It looks at a single line of the image and plots the Red, Green, Blue and Luminance values on an axis. This allows us to directly inspect what a math or compositing operation actually does under the hood.

The Nuke script to follow along can be downloaded here.

The Nuke script for the Merge node session can be downloaded here.