From VFXPedia

Flow Overview

The Flow Editor is displayed below the large image display and is Fusion's primary workspace. The flow provides a schematic-type overview of the structure of the project. Each tool is represented by a tile in the workspace, with connections to and from the tile to indicate how each tool relates to the overall processing of the image result.

This workspace is known as the flow because images move through the connections like water through pipes. By watching the flow of images through the pipes, an intuitive overview of the current image processing operations can be formed.

This view offers tremendous flexibility for connecting tools, including the ability to branch a tool's output into separate streams and collapse entire groups of tiles to view a thumbnail image of a tool's, or several tools', outputs.

The following illustration shows a simple flow. This flow contains a loader that brings footage in from disk and that loader is connected to a resize tool. The resize tool is, in turn, connected to a saver for rendering the result to disk.

The next illustration shows a more complex flow. It combines multiple layers of footage and demonstrates the idea of branching.

Note

Previous versions of Fusion would save projects to disk using the file extension .flw. This was commonly referred to as a flow. The use of the term flow to refer to a part of the interface as well as the saved project caused some confusion. eyeon renamed the saved project to .comp (for composition). As of version 5, the term flow refers to this portion of the interface only.