Massive scene slowdown on keyframing a blendshape

[Steve Davy]

I have a blendshape in my scene that's essentially been used as a model modification and was not intended to be keyframed. Worked great, didn't seem that slow to evaluate even though the geo is quite heavy.

However, I now actually want to add two simple A to B keyframes on the blendshape.

This immediately slows down my scene to an almost unusable state, even when the timeline is outside of the keyframed range, when I'm doing something completely unrelated to animation, not moving the timeline, simply selecting things etc. etc. The entire UI keeps locking up for probably 20-30 seconds.

I have tried disabling all evaluations although since blendshapes are not listed in the types of evaluations you can toggle I'm assuming that's why that didn't help.

WTF? Why would adding keyframes to a blendshape do this? 

[joiec...@gmail.com]

I really don't know. But to be sure, I would try to use MASH blendshape node just in order to confirm it's a blendshape problem or it is another different thing.