How do I calculate all motion before rendering? I am using pairs of empties, 'tracked to' each other to create a piston effect. I spent a long time getting the motion to work so that those empties are children of moving objects. It works OK, but the empties need to be reminded, almost every frame, to track it's counterpart. Is there a way to have blender calculate the motion of the scene so that these tracking constraints work correctly each frame? Any advice?
When the solver has trouble keeping up, like when tracking constraints get lost on a frame by frame basis - here's some advice. The fewer relationships between empties and meshes, the better. If your empty isn't tracking a mesh correctly or copying it's parent's motion correctly then make it's parent an empty. Surprisingly the increased number of empties doesn't make it harder on the solver, but rather makes it work better.