Cineversity

I am returning to C4D after 8 years of doing other things, currently exploring dynamics.
Based on the little “car” object in the html documentation…
https://help.maxon.net/us/#DYNCONSTRAINTOBJECT
...what happens when I play the animation goes against my understanding of how computers work: getting back on its feet (or rollers) again after the thing falls off the end of the ramp is different each time I play the animation - very entertaining and realistic, but I would have expected the result to be always the same for the same input.
I looked for some hidden “variance” parameter in the collider tags - couldn’t see any.

can anybody explain what is happening?

cheers
Günther

Hi Cork City Gamelan,

If you like to have it all the time the same, use the cache and store the simulation.

Thanks a lot for the scene file. Always so much clearer to comment on.

Think of these calculations as a complex formula. Weight, Gravity, Torque, friction, bounce, inertia, etc

Each time there is a result, it describe one frame. From this frame the next calculation is done.
To do this in an manageable amount of time, things are as precise as needed. Let’s say for argument sake, the precision is 99.99%, (I assume it is lower). So the next time the frame has to work with a 99.99% times 99.99% precision.
This would equal 99.98001% or 99.98%. The precision is lowered with each frame. After your set up with 500 frames this little “error” will show.
. Not even to mention the Noise Collision Parameter, to keep things manageable—time wise, but it is certainly the most obvious factor here, besides my little excursion and build up values.
. A scientific correct simulation would perhaps plot a verification from the start parameters, to eliminate rounding errors and concatenate the parameters and situation based relations as far as possible to gain a high precision.
Well, that is not the scope here. The target is a rendering, not a game to play cars, even that is a lot of fun, I admit ;o)

I guess to have nearly 100% repeatable precision would take days on a single workstation, if at all possible on this kind of equipment.

Let’s have a look at your scene, the Friction and Bounce parameter look like to be set up with a 5% increment. This means this is your initial precision in a set up, to start with, the kind of expectation of precision shines here through, doesn’t it, not a proof that the rest could be sloppy, not my point here. I don’t blame here, it is just a simulation for visual representations and not a scientific based result, of a “super computer” repeatable at any place of the world.

So, my suggestion, if you like something keep the cache as is and save the scene. Bake perhaps the movement if that is critical. After baking, perhaps just with a Tracer and a Raid object, you can fine tune the expression, and that lands exactly in the filed of Cinema 4D, to create expressive images as an visual artist.

ENJOY

ah, thanks… it doesn’t bother me the least bit - it actually simulates much more closely what is happening in the Real World where inputs into such a complex dynamic system can never be kept constant and small variations can return very unexpected results. I actually find it very cool and entertaining - it just simply looked to me like an impossible thing to happen on a computer.

Do I understand this correctly:
“baking” a simulation would give me something predictable to show to a movie maker?
could I bake a toy building blocks animation like this one and still be able to replace it with a realistic model ... perhaps using Xpresso? don’t waste time researching and explaining in detail, please, I may never need to do it - just tell me whether it can be done and I’ll figure it out when I need to know.

Amazing how C4D looks totally different now from what I remeber - I prefer the “old” icons - but it seems to work exactly the same way

thanks again
Günther

Thanks for the clarification, Cork City Gamelan. :o)

So, no details no research, as requested!

Being a filmmaker myself, (with many awards and nearly three decades of doing so), I would say: yes, it should be sufficient to show it around. Like animatics or the animated storyboard. The nice side effects of this is (cached or baked), you can work on your camera (Cinematography) while the director sits with you in the session. I found it over the decades a wonderful trainings-place, without building up my jib arm or putting my Steadicam™ on.
So much faster.
Which the camera roughly defined, the amount of work needed normally shrinks, as it becomes clear what is really needed. Short renderings as print outs help even to draw ideas on, and to find an agreement in a quick way.
.

If you can replace later something with a realistic model – you ask…  Well: yes and no. This question is too general to allow me me say anything – specifically. The dynamics will change when you get more realistic. I often see how building collapse in feature films, and I always wonder, if they at least understood how “reinforced concrete” works at all? (I grew up in a construction company and have worked as an architect and engineer long enough to have an idea about it.) Or when they collapse a bridge with a certain construction, how the rest of the bridge would act if things like a partial destruction happen? Certainly they do not at all, but the common audience buys it anyway, and in that range film work is done. ;o)

So, I talk already about details, which you didn’t want to read. Time to stop here. ;o)
For general question you might get only low quality answers, as usual: Many movies look that way and it is very sad from where I look at it. ;o)

My best wishes for your project.

P.S.: have a look here, for more car mischief:
https://www.cineversity.com/forums/viewthread/2083/