Rigid bodies start out wobbling and then fly through passive rigid body floor

So, I have been so excited to work on this. Finally dedicated to learning blender through and through and even more so excited to follow through with the exercises given as well and of course on my first one, I can't seem to get the rigid bodies to even start out standing still or even to really obey the laws of physics.

I have played with the 'solver iterations', 'steps per second', I built my dominos from scratch and made sure they were all to scale and applied scale to everything. Played with friction, and honestly have toyed with every slider I could find related to rigid bodies and still am at a loss. I really want to understand what is going on here.



I am honestly so happy with the scene I created. I just really want to figure out why my physics engine is going crazy one me haha! If you think using my .blend file could help just let me know. Thanks!

  • spikeyxxx replied

    tthepaperkrane 

    Hi Benjamin. Is your ground just a Plane?

    Collisions between objects are calculated by looking at the distance between vertices. As a Plane only has 4 verts at the corners, the Rigid Body solver doesn't recognize a collision.

    Try subdividing the ground...

    If that doesn't help, a link to the .blend file would be very helpful.

  • Benjamin Farnham(thepaperkrane) replied

    Hey there, thanks for your response! 

    So the table is a re-scaled cube (I applied transformations). I subdivided the surface and made sure the shape was set to 'convex hull' and 'deform' and it seems to have really helped. No more falling through the table, but upon start, they rock back and forth and then when it falls it seems to jitter/slide an unusual amount.

    I am playing with the settings a bunch as we speak but just in case you have more insight than I as to why this might be, here is a link to the .blendfile .

    I really appreciate the help on this and hope I can get this animating smoothly soon. I got really excited building out the environment to house these dominos in and by the time I got to animating, I had thought I broke everything hahaha.

  • Jonathan Lampel replied

    Hey Benjamin! After looking at the file, I think you can set the collision type to box. Spikey is right that collision objects are better with some thickness, but there's no need to subdivide if you're not using convex hull or mesh. The primitive collision types are faster to use and more stable, but since this is a simple animation I'm guessing you won't see a whole lot of difference. 

    One thing about rigid body simulations is that they're very unstable at a small scale. I scaled everything up by 5 and that helped a lot. I also increased the steps per second to 350 which got rid of the wobble. Here's the file:

    http://pasteall.org/blend/index.php?id=52325 

    Hope that helps! 

  • Benjamin Farnham(thepaperkrane) replied

    So I checked it out and really saw a difference in the results. It really does look so much better now. Thanks again for taking the time to take a look and help me with this.

    Here I was trying to build everything to scale (which I thought might be rather important for some reason) and I am so glad to learn that it does create some wonkey physics at smaller scales. 

    I am currently in the process of rendering out my exercise so I am really excited to have this one down and also be able to understand why I had some hiccups in the beginning.

    Thanks again!

  • Shawn Blanch(blanchsb) replied

    tthepaperkrane I wonder if your dominos are possibly intersecting just slightly with the floor plane and when playing the physics engine it is trying to start figuring out that dynamic before everything else and then it turns into a wobble? I remember doing some physics stuff and seemed to have that problem when objects started out having already crossed each others' comfort zones of collision detection. Hopefully that makes sense, but perhaps it is just a scale issue.

  • Benjamin Farnham(thepaperkrane) replied

    Hey Shawn,

    I checked that too. I even created space along the bottom after a while and honestly that made it worse haha! What ended up fixing it entirely was the scaling. It was amazing. It was buggy up until I scaled it about 4 times its size then instantly became stable. Thanks for the idea though. I will make sure to watch for it in the future.