User Manual

Disparity and Optical Flow values are stored as un-normalized pixel shifts. In particular, note
that this breaks from Fusion’s resolution-independent convention. After much consideration,
this convention was chosen so the user wouldn’t have to worry about rescaling the Disparity/
Flow values when cropping an image or working out scale factors when importing/exporting
these channels to other applications. Because the Flow and Disparity channels store things in
pixel shifts, this can cause problems with Proxy and AutoProxy. The convention that Fusion
follows is that, for proxied images, these channels store unscaled pixel shifts valid for the
full-sized image. So if you wish to access the disparity values in a script or via a probe, you need
to remember to always scale them by (image. Width/image. OriginalWidth, image. Height/image.
OriginalHeight).
When using Vector and BackVector aux channels, remember that all nodes expect these aux
channels to be filled with the flow between sequential frames.
More precisely, if you have sequence of three frames A, B, C, then:
B Vector will contain the flow B>C
B BackVector will contain the flow B>A
A Vector will contain the flow A>B
A BackVector is written with zeros as there is no frame before A
C Vector is written with zeros as there is no frame D to flow C>D
C BackVector will contain the flow C>B
When working with these channels, it is the user’s responsibility to follow these rules (or for
clever users to abandon them). Nodes like TimeStretcher will not function correctly since they
still expect the channels to contain flow forward/back by 1 frame.
NOTE: Currently DoD/RoI is not supported for all Fusion nodes.
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