User Manual

Optical Flow [OF]
The OpticalFlow node
Optical Flow Node Introduction
This node analyzes a clip connected to its input using an Optical Flow algorithm. Think of
optical flow as a per-pixel motion vector that matches up features over several frames.
The computed optical flow is stored within the Vector and Back Vector aux channels of the
output. These channels can be used in other nodes like the Vector Motion Blur or Vector
Distort. However, Optical Flow must render twice when connecting it to a Time Stretcher or
Time Speed node. These nodes require the channels A. FwdVec and B. BackVec in that order,
but Optical Flow generates A. BackVec and A. FwdVec when it processes.
If you find that optical flow is too slow, consider rendering it out into OpenEXR files using a
Saver node.
TIP: If the footage input flickers on a frame-by-frame basis, it is a good idea to deflicker
the footage beforehand.
Inputs
The Optical Flow node includes a single orange image input.
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Input: The orange background input accepts a 2D image. This is the sequence of
frames for which you want to compute optical flow. The output of the Optical Flow
node includes the image and vector channels. The vector channels can be displayed
by right-clicking in the viewer and choosing Channel > Vectors and then Options >
Normalize Color Range.
Basic Node Setup
The Optical Flow node analyzes the frames connected to the background input. Trimming a
Loader or MediaIn to only the range you need prevents analyzing unnecessary frames. The
output of the node can then be connected to any node that takes advantage of vector
channels, such as a Time Stretcher.
TIP: When analyzing Optical Flow vectors, consider adding a Smooth Motion node
afterward with smoothing for forward/ backward vectors enabled.
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