This patch changes the interpolation algorithm utilized by the Keying
Screen node to a Gaussian Radial Basis Function Interpolation. This is
proposed because the current Voronoi triangulation based interpolation
has the following properties:
- Not temporally stable since the triangulation can abruptly change as
tracking markers change position.
- Not smooth in the mathematical sense, which is also readily visible in
the artists sense.
- Computationally expensive due to the triangulation and naive
cauterization algorithm.
On the other hand, the RBF interpolation method is temporally stable and
continuous, smooth and infinitely differentiable, and relatively simple
to compute assuming low number of markers, which is typically the case
for keying screen objects.
This breaks backward compatibility, but the keying screen is only used
as a secondary input for keying in typical compositor setups, so one
should expect minimal difference in outputs.
Omar Emara