Contact Support

How 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.

Three Transform nodes that concatenate. The image is only filtered once.	A Crop node between the Transform nodes breaks concatenation. The image is filtered twice, resulting in poor 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.

When nodes concatenate, Nuke only uses the filtering method set on the last concatenating node (in this case, the filtering method used is Mitchell).

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.

Nodes that concatenate	Only concatenate upstream	Do not concatenate
Card3D	BasicMaterial	AdjustBbox
CornerPin	Diffuse	BlackOutside
Reconcile3D	DisplaceGeo	Crop
Reformat	Displacement	Mirror
Stabilize	Emission	PlanarTracker
Tracker	Environment	PointsTo3D
Transform	Flare	Position
Dot	GridWarp	TVIScale
NoOp	IDistort
Switch	LensDistortion
Disabled nodes	MotionBlur2D
	Phong
	Sparks
	Specular
	SphericalTransform
	SplineWarp
	STMap
	Tile
	TransformMasked