User Manual

Smoothness
This controls the smoothness of the optical flow. Higher smoothness helps deal with noise,
while lower smoothness brings out more detail.
Edges
This slider is another control for smoothness but applies it based on the color channel. It tends
to have the effect of determining how edges in the flow follow edges in the color images. When
it is set to a low value, the optical flow becomes smoother and tends to overshoot edges. When
it is set to a high value, details from the color images start to slip into the optical flow, which is
not desirable. Edges in the flow end up more tightly aligning with the edges in the color images.
This can result in streaked-out edges when the optical flow is used for interpolation. As a rough
guideline, if you are using the disparity to produce a Z-channel for post effects like Depth of
Field, then set it lower in value. If you are using the disparity to perform interpolation, you might
want it to be higher in value.
Match Weight
This control sets a threshold for how neighboring groups of foreground/background pixels are
matched over several frames. When set to a low value, large structural color features are
matched. When set to higher values, small sharp variations in the color are matched. Typically, a
good value for this slider is in the [0.7, 0.9] range. When dealing with stereo 3D, setting this
option higher tends to improve the matching results in the presence of differences due to
smoothly varying shadows or local lighting variations between the left and right images. The
user should still perform a color match or deflickering on the initial images, if necessary, so they
are as similar as possible. This option also helps with local variations like lighting differences
due to light passing through a mirror rig.
Mismatch Penalty
This option controls how the penalty for mismatched regions grows as they become more
dissimilar. The slider provides a choice between a balance of Quadratic and Linear penalties.
Quadratic strongly penalizes large dissimilarities, while Linear is more robust to dissimilar
matches. Moving this slider toward Quadratic tends to give a disparity with more small random
variations in it, while Linear produces smoother, more visually pleasing results.
Warp Count
Decreasing this slider makes the optical flow computations faster. In particular, the
computational time depends linearly upon this option. To understand what this option does, you
must understand that the optical flow algorithm progressively warps one image until it matches
with the other image. After some point, convergence is reached, and additional warps become
a waste of computational time. The default value in Fusion is set high enough that convergence
should always be reached. You can tweak this value to speed up the computations, but it is
good to watch what the optical flow is doing at the same time.
Iteration Count
Decreasing this slider makes the computations faster. In particular, the computational time
depends linearly upon this option. Just like adjusting the Warp Count, adjusting this option
higher will eventually yield diminishing returns and not produce significantly better results. By
default, this value is set to something that should converge for all possible shots and can be
tweaked lower fairly often without reducing the disparity’s quality.
Filtering
This option controls filtering operations used during flow generation. Catmull-Rom filtering will
produce better results, but at the same time, turning on Catmull-Rom will increase the
computation time steeply.
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