Can't render multimachin when using physics and depending on a collision

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#1

As you may have seen in the discussion for other lectures, I animate my lamp using Inverse Kinematics, but have a rigid body on the lamp shade and base. The lamp collides with a bowling ball to start it rolling thanks to the physics engine. It rolls under the control of physics, before colliding with the bowling pins. It works when rendering on a single machine.

I’ve tried using multiple machines on dropbox as in the videos. Here’s what happens. On the machine that launches first, everything proceeds as expected. The ball never starts rolling on the machine that launches second, however, apparently because it’s already past the point of collision.

Here’s the really weird part, though. The pins don’t show on the machine that’s missed the original collision. I get why the ball doesn’t start rolling but I don’t know where the pins have gone.

Does this mean that physics (and perhaps particle systems) won’t necessarily work when done as shown in the videos?

Brian

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#2

Not sure what you are trying to do.

But sometimes I render on multiple machines, working on the same project .blend file.
Or another trick was to start two blender sessions on one machine. Also rendering the same project.
But one in CPU mode, the other in GPU mode. But I stopped this, because it overheated my laptop.

But in all cases, I never rendered to video but to stills instead. Rendering even/uneven frames. Combining them in another session as a video.

Dropbox is an FTP program, your files are transferred to a server. Meaning you are not sure if your data on servers and PC’s are up to date (nature dropbox). I can imagine that Blender has problems in managing temporary files using dropbox.

#3

I’m trying to render on multiple machines using the same .blend file using dropbox as recommended by the instructor in the videos. It doesn’t seem to work if the second machine didn’t see the collision that starts the ball rolling.

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#4

What happens, if you copy the blend file from the dropbox onto the local machine.

#5

The blend file is synced from dropbox and exists on the local machine.

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#6

The location for the .blend is somewhat the root for all Blender file IO (relative paths).
So can it be that Blender does something on that Dropbox folder, which is too fast or slow for other synced systems?

#7

I always thought, and it must be how it works, that you can render any frame on any machine. If you can be bothered with all the faffing about.
Animation and physics probably need to have been run an ‘baked’? Perhaps there is some way that needs saving? So every frame has a record of where things are.

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#8

Ah, good call. I’m guessing I need to bake the physics simulation. I found this Baking Physics Simulations — Blender Manual

This says: “It is generally recommended to bake your physics simulations before rendering. Aside from no longer needing to go through the time-consuming process of simulating again, baking can help prevent potential glitches and ensure that the outcome of the simulation remains exactly the same every time.”

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#9

Thanks for the link. Very useful info. :slightly_smiling_face:

#10

Update: Turns out that baking physics is really easy and fixes the problem I was having. All you do is select the objects with rigid bodies that are controlled by the physics engine. Then go to Object->Rigid Body->Bake to keyframes. From there, the multimachine render using dropbox works as described in the videos.

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#11

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