Windows 10 Home
Nvidia GTX 960
Broken: v2.78 4bb1e22
In NLA editor, when blending two (or more) tracks using Add mode of action blending. If both tracks contain location, rotation, or scale keyframes, they will be added together even if the second track was based on animation from the first. i.e. both track have objects at a scale of 1 resulting animation will be scaled to 2. If locations are set in the same place for each track the they will be added instead of being blended, Rotations will also be added instead of blended. There are no sane use cases for this, indicating it is a bug. Both expected and desired functionality, which includes countless use cases (including standard work flows), is for only differences between a lower track and a higher track to transform the keyframes. Subtract yields similar, useless results.
Exact steps for others to reproduce the error
1 - Create an animation with keyframes for rotation, scale, and location
2 - Using NLA Editor, "push down" the animation into a track.
3 - Switch action blending to add.
4 - Create another animation to blend with the first, using keyframes location, scale, and rotation.
5 - Play animation and watch the madness ensue.
6 - Ask yourself if this is not a bug, what possible use case could there be for Add, Subtract, and Multiply action blending modes?
7 - Imagine the possibilities if this is fixed. Animation layers, blending mo-cap, the possibilities are endless.
Thanks for making Blender so amazing.