Wednesday, March 17, 2010

The After Effects to Nuke Migration: Speaking Nuke

As a compositing artist, it’s just as important to have a breadth of knowledge across several applications as it is to have a depth of knowledge in a particular vendor’s product. Recent changes in the marketplace have made Nuke, originally developed over 15 years ago at Digital Domain, the hot application of the day. For those migrating from After Effects, as I have done, our knowledge of compositing techniques and disciplines will help us grasp the key essentials quickly. This article will compare and contrast After Effects and Nuke to help you make the transition.

The essential difference between Nuke and After Effects is not that one is node based and the other is
not; in fact both are node based, multi-layer (let’s say multi-stream from now on) one pass compositing applications. [See my article Decomposing Node-based Software.]

The differences can be classified as:
  1. Terminology differences
  2. User interface differences
  3. User work flows differences
  4. Compositing toolkit differences
  5. Differences within analogous tools
This article will not attempt to explain all these differences, but rather, focus After Effects users on how to think and speak in Nuke with regard to terminology and interface.

User Interface Differences

When an artist cracks open Nuke for the first time, it can appear overwhelming. There is much more information on the screen than in After Effects and seemingly more controls and options. Further, the icons and placement of controls are unfamiliar. I had the same experience when I transitioned from Composer to After Effects. It’s new software shock, and the best treatment is to start learning where the controls are you often use and what are all those other thingies for? My best advice –go do the online Nuke tutorials. These will help you learn the controls, and the interface is divided into several areas so each tutorial video is only a few minutes long.

But let’s look at this from your perspective as an After Effects artist, shall we?

First, your life in After Effects begins with your project window. This is where you gather footage and manage compositions and other assets. Nuke has need for such things, so just say goodbye. It also has no interface similar to AE’s Timeline. Instead, all footage items, composition trees, and effect nodes coexist in happy arrangement or chaotic confusion (depending on the user) in an area called The Node Graph. (key frames and motion curves can be viewed and edited in the Curve Editor). Unlike After Effects’s Node Graph, which shows only one composition tree at a time, the Nuke Node Graph allows the artist to view all compositions at once. Well, this may be impractical, but the artist will zoom into a comp or branch of a tree to work on a particular area while leaving the rest of the node graph outside the desktop boundary. So Nuke’s Node Graph IS the Project Window and the Composition Window.
After Effects users may miss the Project Window, which functions as a Project Bin for sorting and collecting footage. While not necessary, an artist can accumulate all the footage items in one corner, place them in an open container called a Backdrop, and then clone these footage items for use in comp node trees. Clone? Yes, Nuke has the concept of cloning a footage item. Think of this as a way to make clear that the same footage with the same settings is being used again. If you change it once, you change it everywhere. Very After Effects like.

User Interface and Terminology Correlation

By now you’ll notice that the language of Nuke is different. Here’s a simple table with a few common terms:

Project Window
Node Graph
You can make a “Project” area in the Node Graph (see text)
Node Graph

Curve Editor
Access “layers” and “effects” on these layers in the Node Graph.
Display and edit curves
Graph Editor
Curve Editor
Nuke has a Maya-like, superior Curve Editor
Composition Window
Footage Window
Layer Window
Viewer All images in Nuke are displayed in a Viewer. Each viewer can have up to 10 inputs (these are “live” unlike AE’s four static snapshots)
Effects and Presets Toolbar No presets. Nuke uses macros called Gizmos, accessed from File menu.
Project Settings
Composition Settings
Project Settings Nuke image formats are determined either in Project Settings or in image generating nodes.
Renderview Write node / Progress Bar Render settings are specified using Write nodes. Progress is monitored using the Progress Bar. There is no visible list of all renders. Renders happen in parallel but user may prioritize this.
Import Footage Read node

Effect Controls Properties Bin Essentially the same. Can limit number of nodes (effects)
Solid Constant node

Shape, Mask, Paint effect, Vector Paint effect, Stroke effect Rotopaint node

Layer No such concept The behavior of working with a layer can be matched by Grouping a Read node and its downstream effect nodes without a Merge node. Alternately a user could highlight a set of nodes using a Backdrop node. Grouping emulates the behaviors of AE layers and AE nested comps.
Effects Effect nodes

Modes Merge node operations Merges in AE are implicit. In Nuke they must be explicit using a Merge node. Merge node “operations” match AE “modes” with the same name.
Eye icon (display/use) Disable on/off A standard node control
Render Quality icon Controlled in Viewer User may work in auto-proxy mode or full resolution mode, and may skip-out pixels.
Motion Blur controls Controlled in nodes that could generate motion or effect motion blur quality. On by default in Nuke.
Color Settings/ Working Space Handled in Read and Write nodes. Display is controlled in Project Settings. Nuke uses a linear floating point space for image processing. All footage is conformed on input and output as needed.
Layer Transforms Transform node

Layer Material Card node Nuke handles 3d very differently. Essentially imported footage (Read nodes) are made 3d using either a Card3D node or a Card node. Choice of node determines other nodes required to render a 3d scene.
Motion Tracking Tracker node
Camera Tracker node
Nuke uses nodes to add tracking functionality. “Tracker” is similar in operation to AE.
Smoother, Wiggler Curve Editor function Curves can be smoothed using a filter function in the Curve editor. Noise is added with expressions.
Pick whip Animation drop work flow In AE a user selects the destination and then requests an animation link, which writes an expression. In Nuke the action is source to destination.
Adjustment Layer No such concept In Nuke, you would use a node with an appropriate mask.
No multi-layer footage 1024 layers with 1-4 channels each Nuke “layers” exist within a image data stream. For example, a Read node could deliver one stream comprised of RGBA, Specular RGB, Reflection RGB, shadow mask, occlusion mask, etc.

This list does not exhaust all the possibilities for comparing Nuke and After Effects, but does hit on the most important.

Let’s take a look again at the difference between an After Effects “layer” and a Nuke “layer”. They are in no way the same, but e the same inspiration: Photoshop.

In Photoshop, a single image (this is important) contains numerous layers. Each layer has channels, 1-4 usually, and each channel is comprised of an array of pixels.

In After Effects, a Comp is analogous to a Photoshop file. If you ever import a Photoshop file into After Effects and keep layers, what you get is a comp. Consequently, in AE, comps have layers and layers have effects and are merged with lower layers using modes.

In Nuke, the image data stream, which often begins with a Read node, is analogous to the Photoshop file. As a consequence, the data stream has layers. These can be merged with other layers in the stream using Merge or ChannelMerge nodes and similar nodes. In Photoshop or After Effects you can rearrange the precedence of layers, turn them on or off, and set merge modes. In Nuke, this work is done using nodes to explicitly merge or move the layers into the data stream and delivered to the Viewer node or Write node.

Nuke Freedom

Despite the terminology and user interface differences, After Effects artists should find the move to Nuke somewhat liberating. Although some things will take more steps to set-up using nodes, this time loss will vanish as artists experience the freedom of not being confto a layer. While some AE effects cut through the layer boundary, the AE layer functions like a closed room. In Nuke, you can close off portions of your composition node tree by enclosing them in a Group node, but this would be for your convenience only.

Another freedom I like in Nuke is the ability to clone items. I mentioned before cloning Read nodes, which an artist could do to provide a Project Bin sort of functionality. In Nuke, ANY node can be cloned (I’m sure that nodes like Project Settings and View would probably be exceptions). For example, suppose you have 10 image clips and want to apply the same color correction and filters to them. After reading each with a unique Read node and giving each a unique Write node, you can set up your correction and filters on the stream, then clone selected nodes to all the others. A change on any will effect all the clones. Essentially, a clone has a unique input and output, but all other parameters are locked to the other clones.

Nuke’s widget making capabilities remind me of Wavefront Composer’s macros, only better. It is a simple matter to desing a workflow, assign variables, and save this as a macro called a widget. After Effects presets are similar, except you don’t get to define variables, and a preset merely attaches the effects to a layer, while a macro/widget lives outside your Nuke script.
Nuke also gives you tons more information feedback than After Effects. In the Viewer, you get a display of pixel colors and coordnates (like AE’s Info) but you also get a list of all the layers in the stream image resolution and an overlay showing the bounding box. In the Node graph, most nodes will report channels are being modified and which are being passed unchanged. Other Node Graph indicators flag a node to indicate if it is animated, has expression links, is a clone, and other useful information.
Another powerful Nuke feature you will enjoy are the Viewer display override controls. Ever look at something on a video monitor and reach out to tweak the knobs? In Nuke, you can tweak your display settings without touching the data. This allows you to look at details in blacks, whites, mids, etc. You can even view the data (and usually do) in a colorspace different from the one Nuke does its work in.

That’s a nutshell of some of the similarities, differences and advantages of Nuke. It’s not a tough process to migrate, you just need to give it a little effort and time. Do the online tutorials and watch the online videos. Best of success.


ABM said...

Very informative. Thanks a lot!

Anonymous said...

Thank you very much !

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