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How Your Nodes Concatenate

Concatenation is behavior that some Nuke nodes perform when you have several nodes transforming your image one after another. When nodes concatenate, they pass on these adjacent transformation operations to the last transforming node in the row, and the last node then performs all the transformations at once.

For example, if you have three Transform nodes in a row, instead of performing each transformation separately and filtering the input image three times, Nuke combines the transformations into one operation and only filters the image once. As filtering unavoidably destroys some image detail, it’s important to concatenate as many nodes as possible in order to preserve image quality.

In order to concatenate, the concatenating nodes have to be adjacent. So, if you have a node that doesn’t concatenate (a Crop node for example) between two concatenating nodes (for example Transform nodes), no concatenation occurs.

If you’re using more than one filtering method in the nodes that concatenate, the last filtering method in the series of concatenating nodes is applied on the result.

As a rule of thumb, the only nodes that concatenate are usually transform nodes. In addition to these, Dot, NoOp, Switch nodes and disabled nodes do not break concatenation.

Color nodes do not concatenate because Nuke works in a 32-bit float, which is enough to avoid banding and visible round-off errors in color.

Please be aware that some transform nodes do not concatenate and should not be interspersed with those that do. There are also transform nodes that receive concatenation, but don’t pass anything on.