Rigid Body Cache BUG? Objects messed up after reopen blend file.

Support Particles and Physics Simulations
1

Hi.

I’ve got problem with Rigid Body Cashe. I bake calculations, quit blender - and reopen that file. My Rigid bodys are all messed up except frame 0. I don’t know even what to type in google/forum to find fix.

Rigid body cache is there, I can only free bake, and rebake it - and it’s ok, but I can’t have it like that, because if it crashes… I’m in deep…

Any clue?

2

Make sure you save your file before you close. But you have to know that editing any object in your scene in any way will outdate the cache so if you open your file and move an object or do anything, your cache will be outdated. I cant remember if outdating the cache will mess up the objects but I do know that Blender pretty much forces you to rebake your rigid bodies. Anyway, hope I helped!

3

Well… that’s not the case. I can free bake, don’t change anything, and still it is not deleted - so no parameter is changed.

Only semi-solution for this is bake to animation, but I would like to avoid that right now.

Any other clues? What can make objects flip after reopening blend file.

4

That is strange. It might just be a way you are manipulating the chache. I have had troubles with caches before and still do. I would go look for tutorials or manuals on Blender’s caches. I just don’t know enough about them.

5

What exactly do you mean when you say it’s messed up?
When you delete and add objects to the rigid body group after baking, objects can change places.
In that case free the bake, if cache is not invalidated select a rigid body, go in and out of edit mode. and resimulate.

6

Ok, little more:

I’ve got car. Car is detailed group of objects. Those objects are parented to the simpler “skeleton” of the car, that is rigid body (for easier calculations). There are some constrains between them.

I don’t change anything in the project (or at least I can make a scenario when I open file, bake all, save, quit, open again and rigid bodies are messed up.)

Messed up = hull of car is rotated in 90 degrees, doors stays in place, weels are not in proper positions.

I found that:

  1. Only first frame is good = all bodies are in correct place.
  2. I can work on baked sim without problem untill I quit.
  3. If I want to Bake to Animation, I HAVE TO bake it from frame 0-end of animation (for example 0-450). If I bake it from 50-end, or even 2-end animation is “messed up” like I would quit blender.

it’s hard to repeat from clean file, because that kind of suprises always come out in little more complex scenes, and I don’t even know how can I recreate that.

7

So only the rigid bodies have wrong transformations?

The reason the start frame is always ok is because there is no simulaion data and we jut use blender regular transformations.

I’ll try and look into it, but without a file or steps to reproduce it’s hard.