Bezier warp generates unwanted vertices and tangents animations
Newbie here with a question (thus potentially dumb).
I am trying to bezier-warp animate a rectangle to sort of mimic the animation of windows reveal/hide on mac.
The rectangle is originally at the bottom of the composition viewport. Its vertical size is roughly a third of the composition height.
Here are the steps of the animations:
- move top left and right vertices and their tangents (the ones of the top edge of the rectangle) to the vertical middle of the "empty" space above the rectangle.
- move the top left and right vertices to the left and right edges of the composition viewport respectively.
- move up the side tangents connected to the aforementioned vertices in order to preserve their original distance from their own vertex.
- move top left and right vertices and their tangents (the ones of the top edge of the rectangle) to the top edge of the composition.
- move the side tangents connected to the top vertices sideways until they reach the edges (left/right respectively) of the composition and are aligned with their associated vertex. Then move up these side tangents in order to preserve their original distance from their own vertex.
- move the bottom left/right vertices and their tangents (the ones of the bottom edge of the rectangle) up until the rectangle height reaches the same height/width ration it originally had.
- move the side tangents associated with the bottom vertices up to preserve the distance from their associated vertices.
Until this point things animate as I would expect and I get a sort of warped trapezoid shape with the top edge the width of the composition, the bottom edge it's original width and the height is the ratio of the original height based on the composition width.
So far so good. Now I want to warp the bottom of that shape and increase its width to morph that trapezoid back into a rectangle.
- move the bottom edge vertices and their associated side tangents sideways until they reach the left/right edges of the composition respectively.
For a reason that is beyond my understanding this does not work as expected. Instead of moving just sideways, the vertices and tangents move up and then down without any apparent reason. The values at the keyframes are correct but the interpolation seems just random.
I assume this is a "normal" behavior because I have re-done this animation several time to make sure it was not a human error and this always happens.
Is there a setting to this script I haven't noticed to prevent this from happening or some further documentation I should read to understand how and why this happens?
Any help would be much appreciated!