Datasheet

■ Layers vs. Nodes 7
Layers vs. Nodes
After Effects and Nuke exemplify the two major approaches to composit-
ing: layer based and node based. Layer-based programs represent each
imported and utilized digital still or image sequence as a layer along a time-
line. Each layer possesses its own set of transformations and special-effect
filters. The layers are stacked and processed in order from bottom to top
(see Figure 1.5). If there are three layers, the bottom layer and middle layer
are blended and then the result is blended with the top layer.
Node-based programs, on the other hand, represent each imported
and utilized digital still or image sequence as a node. The output of a node
is connected to the inputs of other nodes, which may be special-effect filters,
input/output controls, and viewers (see Figure 1.6). Any given node accepts
a limited number of inputs. However, the output of a node may be con-
nected to an almost unlimited number of nodes through their inputs. Node,
as a term, refers to a discrete unit used to build linked data structures. The
data structure in Nuke and similar node-based programs is referred to as a
tree graph, node tree, or node network. More specifically, the structure is a
Directed Acyclic Graph (DAG), wherein data flows in one direction along
the node connections. The direction is usually indicated by arrows.
There are several advantages to layer-based programs:
Layers are intuitive to use. It’s fairly easy to imag-•
ine the result of dropping one layer on top of
another, particularly when the majority of digi-
tal artists are familiar with the Photoshop layer
workflow.
You can quickly set up a simple composite utiliz-•
ing a limited number of layers. The same simple
composite in a node-based program can require
additional steps. For example, Nuke may require
the addition of a Bezier node whereas After
Effects automatically provides the Pen tool.
When layers are stacked, they are merged auto-•
matically. A node-based program requires some
type of merge node to supply the blending mathematics.
There are several advantages to node-based programs:
You can use the output of one node as the input to numerous other nodes. Although •
you can nest composites in a layer-based program, it becomes difficult to manage on
complex projects.
Once you are familiar with a node-based workflow, complex node networks are easy •
to interpret. Inputs and outputs in a node network are clearly indicated by node con-
nection lines. With a complex layer-based composite, it becomes difficult to trace
inputs and outputs because the main graphic representation only indicates position
within a layer outline of a particular composite.
Generally, node-based systems do not require precomposites, or • precomps. Precomps
are necessary with layer-based systems because it is difficult to send outputs of par-
ticular layers or filters to the inputs of other layers.
High-end feature animation and visual effects work is generally created on node-based •
systems. Flame, Inferno, Shake, Fusion, Toxik, and Combustion are node based.
Figure 1.5 The layer outline in the
Timeline panel of After Effects. The
11 layers are processed in order from
bottom to top.
Figure 1.6 A Nuke node network with five nodes. The
arrows of the connection lines (pipes) indicate the
direction information is flowing.
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