Hello all,
I am trying to figure out manually, the point p at which the layer will be present at a given time t. Consider I have a star layer and it’s origin is animated from (0, 0) to (60, 0). The interpolation type is linear. So according to the Synfigcode, the in-tangent and out-tangent both will be equal to 60. But these needs to be scaled by a factor of 3.
So finally, to calculate the hermite curve, we need 4 control points(link).
So, for the hermite curve of x-axis: P0 = 0 P1 = 60/3 = 20 P2 = 60/3 = 20 P3 = 60
Hence the curve will be written as:
P(t) = (1 - t)^{3} * 0 + 3(1 - t)^{2}t * 20 + 3(1-t)t^{2} * 20 + t^{3} * 60
where 0 < t < 1

Let us take t = 0.5:
P(0.5) = 22.5
This is the answer we get after evaluating the curve. But intuitively and also the value at t = 0.5 in Synfig UI is 30.

Could anyone explain where am I wrong here, or where am I making the mistake. I have been stuck on this for quite a while. Any help would be much appreciated!
I am attaching the .sif file here: star_check.sif (2.8 KB)

One more view regarding the above:
When the interpolation type is linear or when the interpolation is TCB but it is on the first waypoint(link), does Synfig still use the hermite curve to evaluate the expression?
I could not find anything else than hermite curve being used… Am I missing somewhere to look?
-Anish

Thanks a lot @blackwarthog and @KonstantinDmitriev!
Now things are getting much clear than before. I guess now interpolation in the lottie-exporter will be much more similar to that of Synfig's actual interpolation. As I was using bezier curves before.