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Stuggz

Dynamic inertia

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Hi - I'm quite new, please excuse my cluelessness!

 

I've had some success with colliders, dynamic bodies etc but am stuck on one particular usage.

 

I want to slide in a flat horizontal object with other unsteady objects resting on it, then have the holder stop and the resting objects topple a bit. Kind of like a tray of tall drinks that wobble/fall over when the tray stops moving.

 

So, normal dynamic objects have too much wobble in the first, smooth-moving phase... but when i keyframe the dynamic tag's 'enabled' property from off to on, things jerk crazily when the change happens.

 

So I'm interested to know, how would you more experienced users tackle this sort of task? Any tips?

 

Thanks in advance,

 

Stuggz

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I haven't managed to reproduce your problem - can you post an example scene ? You can control wobbling with angular and linear damping in the dynamics tag. Things suddenly exploding is often due to intersection.

 

The 'glasses' fall over in this file

 

fallover.c4d

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First, have you let your objects fall onto the plane (with a Collider Body tag) and click "set initial state" in the dynamics tags.  Then you may want to try switching the Trigger from "Immediately" to "At Velocity Peak."  Put your tray and other objects in a null and animate the null using bezier keyframes.  When it reaches it's fastest speed, the objects will become dynamic and fall over when it stops.  Play with friction, follow position/rotation, and dampening settings to get the look you want.

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Thanks both, I think I've cracked it now. Great tips. I think my problem was a mix of having wonky project dynamics settings and not having the correct initial state.

 

A side-problem though, is that my object, which I want to appear really heavy, appear really light like hollow plastic, despite setting custom mass to 10000 and dampening the linear and angular settings, and turning bounce to 0%... no biggie though!

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re: big heavy things - although physics tells us that all objects fall at the same speed under gravity, in C4D big objects seem to fall differently to identical smaller objects

 

2cubes.c4d

 

maybe you should make your scene bigger ...

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I dunno, @jed.  This seems pretty accurate to me.  Just because everything in the real world falls at the same speed in a vacuum, doesn't mean the simulation of a small thing will look the same as the sim of a big thing.  Would you really expect a skyscraper to fall over just as fast as a domino?  No, because the top of the skyscraper is hundreds of feet higher than the top of the domino, so it has much further to travel.

All that said, yes, scale does matter when doing simulations.  If you want it to look like wine glasses tipping over, you should make your objects the size of wine glasses (not the default 200cm cube!).

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Thanks again guys, you have both been very helpful. 

 

My objects are in a big complex scene with lots of scale-dependant things like S&T lines whose thickness depends on distance to camera...

I'll go and experiment a bit myself later anyhow, but just wondering, if I scale the whole project in project settings, how much of those kind of settings get scaled accordingly...?

 

S

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I'm not sure about scale of S&T, but if it is camera dependent, I would think you'd be OK.  As for your sims, get them how you like them at whatever scale works, then try baking everything and then scaling the project.  I haven't tried it, but in theory it should work.

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@natevplas It was something I saw in a tutorial about collapsing buildings - the guy had a building made of small cubes, and it didn't look right, but scaled up it looked more realistic.

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@jed interesting... So, he had it at the correct scale, but had to scale it up to the size of a mountain or something?  It doesn't surprise me :P

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