User Manual

An Optical Flow node generating motion vectors on-the-fly
Alternatively, if you find the Optical Flow node too slow to analyze the frames, consider
rendering it out to an OpenEXR format using a Saver node. Then import the rendered EXR file
as your new image with embedded vector channels.
An Optical Flow node rendered out through a Saver node
Inspector
Controls Tab
A single slider at the top of the Controls tab improves performance by generating proxies. The
remaining Advanced section parameters tune the Optical Flow vector calculations. The default
settings serve as a good standard. In most cases, tweaking of the advanced settings is not
needed. Many deliver small or diminishing returns. However, depending on the settings,
rendering time can easily vary by 10x. If you’re interested in reducing process time, it is best to
start by experimenting with the Proxy, Number of Iterations, and Number of Warps sliders and
changing the filtering to Bilinear.
Proxy (for Tracking)
The Proxy slider is used purely to speed up the calculation of the optical flow. The input images
are resized down by the proxy scale and tracked to produce the optical flow. The computational
time is roughly proportional to the number of pixels in the image. This means a proxy scale of 2
will give a 4x speedup, and a proxy scale of 3 will give a 9x speedup.
Chapter – 101 Optical Flow 2243