I am improving the quinema program with several things that I would have liked to have during the development of the 4232, such as an animation assistant that adds interleaves to my drawings or the ability to sketch and see the results in moments.
Inbetweening based on 2 drawings
Sketch to Draw
Oh boy this is like a Morph, so great. 
I takeout my hat infront you.
Is this a program you are developing that draws in-between key frames based on two different sketches?
Yes, between two sketches or two finished drawings.
When the development improves I publish it as software libre