This lesson does not try to teach every Fusion node. It teaches you how to read the Flow, use the Viewer, keep the graph organized and locate the point where an effect stops working.
Think in data flow, not layer stacks
In Fusion, the image travels from node to node. MediaIn is a source, tools modify data, Merge combines branches and MediaOut returns the result to Resolve. If an effect disappears, follow the chain until you find where the output changes.
Viewer: always know what you are looking at
Send nodes to the left or right Viewer and compare an intermediate result with the final composite. This is much faster than randomly disabling tools.
Flow: grid, connections and direction
Arrange nodes left-to-right by purpose so the graph becomes its own documentation. Use grid alignment and clear connections, and group long branches by function: keying, tracking, text, color and output.
Bookmarks and navigation in large comps
Bookmarks are useful once the graph no longer fits on one screen. Create navigation points for important areas such as Tracking, Main Composite and Output, then jump between them instead of constantly panning.
Precision and performance
Do not increase processing quality and precision without a reason. Heavy blur, particles, 3D and optical-flow tools consume resources quickly. While building, temporarily bypass expensive branches, use proxies/cache and return to full quality for final checks.
Debug one node at a time
When a graph breaks, do not rebuild everything. Bypass the suspicious branch, inspect the node input and output, then continue downstream. Systematic checking is almost always faster than random changes.
Key takeaway
Fusion becomes much easier when the Flow reads like a process diagram. Viewer discipline, clean organization and systematic debugging matter more than memorizing hundreds of nodes.