Rigid Body With Initial Rotation is Losing Rotation if Initial Location is Changed

Edit: Thread title should read: “… is Changed or File is Saved”

Note: I can’t upload the test blend as I originally planned because the problem outlined below also occurs if the file is saved (even without translating the second monkey).


Two monkeys falling onto a plane.

The first is a simple rigid body (active).

The second is also active, but has its “animated” property keyframed ON for the first two frames, then keyframed OFF in the third frame. In frame 1, a rotation keyframe is assigned. In frame 2, the monkey is rotated slightly around the z axis and another rotation keyframe is assigned.

This is the procedure used at the very start of blendercookie’s tutorial where a number of buttons fall down spinning to form an image of their mascot (http://youtu.be/iYL9w6xsZ6g)

If I could attach a working blend file, and if you loaded it and immediately pressed Alt-A to run the animation, you would see the first monkey fall down with no rotation, and the second monkey fall while rotating during the entire fall. So far so good.

BUT, just grab the second monkey and translate it up on the z axis a small amount. Hit Alt-A, and this time the second monkey rotates only between frame 1 and 2 and then falls down with no further rotation. I’ve checked the keyframing, and they all seems OK.

The problem also happens if the file is saved without translating the second monkey upward.

Any ideas why the simple translation or file save seems to mess this up? Thanks!

Note: This file demonstrates the result of the problem. I can’t upload a working one since saving the file creates the problem.
Impart Initial Rotation to Falling Object 01.blend (569 KB)

don’t quote me, but I had a similar issue when I was moving an object after I simulated. As soon as I did that the object just stayed at its final resting place when I went to simulate it again. So I was forced to go and reposition the object back to it’s starting point and try simulating again. I was told by the developer that by me doing translating after simulating was why the problem was occuring.

I think that is just what is occurring in your situation. Why this occurs, I cannot say, but just thought you might want to reconfirm that its not a problem with your settings or anything.

Thanks for that. I know I need to do some more troubleshooting and your post gives me some ideas about what to test. The fact that simply saving the file seems to recreate the problem is suspicious and might point to a problem with my system. However, that blendercookie tutorial goes on to suggest there are some bugs with the behavior of keyframing the animate button (particularly when trying to duplicate objects), and he ends up using a different method entirely. I’m not sure his bugs are related to the behavior I’m observing, but I just wanted to try his method on a single object. Thanks again.

That’s actually a bug that’s fixed now. Should work fine in 2.66a :slight_smile:

Great. Off to download. Thanks!!