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Dear Blender Community,

There's quite a few posts discussing the interaction of rigid body objects with cloth and soft body objects, but I haven't yet found one that provides a satisfactory answer to the following question:

how do you set up a cloth (or a soft body object) that responds differentially to the different rigid body parameters of an impinging object?

Here's what I'm trying to do. I'm trying to set up a scene where an object drops onto a cloth in such a way that the mass of the object makes a difference in how deeply the object sinks into the cloth. A quick, excellent tutorial in Cinema4D was enough to achieve this effect relatively well.

My simulation in Cinema4D begins like this:

Initial Frame of a Rigid Body / Soft Body Interaction

and ends like this:

End Frame of a Rigid Body / Soft Body Interaction

the only difference between the left and right being the masses of the balls.

I've yet to find a technique that does this nearly as well in Blender, but I would infinitely prefer to use Blender over Cinema4D.

I'd be much obliged to any good samaritan out there that would tell me how to obtain a similar effect with good old Blender.

My thanks in advance.

Edit: Here's a GIF of the full simulation:

Full Rigid-Body / Soft-Body Simulation on Cinema4D

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    $\begingroup$ There is no two way interaction between softbodies and rigid bodies or cloth and rigid bodies. $\endgroup$
    – Leander
    Commented Sep 25, 2018 at 10:45
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    $\begingroup$ I appreciate your trying to use Blender over Cinema4D $\endgroup$
    – user61976
    Commented Sep 25, 2018 at 20:46
  • $\begingroup$ Apparently this is a very difficult thing to pull off as of 2017, within Blender. Check out this answer to a similar question: https://blender.stackexchange.com/questions/73780/how-to-make-cloth-catch-a-falling-object-slowing-its-fall#73812 $\endgroup$
    – Matt Jones
    Commented Sep 25, 2018 at 21:33
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    $\begingroup$ You can fake it by building a "cloth" out of rigid bodies. Are you interested in the solution as seen in the gif. It is overly complex and not as production-fit as cinema obviously. $\endgroup$
    – Leander
    Commented Sep 26, 2018 at 20:57
  • $\begingroup$ Thanks for the responses, @Leander I'm a little hesitant to use anything that's not explicitly a simulation, per se, but I'm very impressed that such a thing is possible with rigid bodies! Also, I'm not sure (on the basis of StackExchange pragma) that I should mark such a thing as the correct answer, but I could certainly post a separate question ('How to simulate a two-way soft body / rigid body interaction with rigid bodies alone') and you could post your answer there? What's generally the best practice here? $\endgroup$
    – Colin Conwell
    Commented Sep 27, 2018 at 0:07

1 Answer 1

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To do this: You would need one plane to serve as the cloth, and one UV Sphere to serve as rigid body. You would have to give the plain a cloth simulation (as soft body isn't what you want), and then the the UV Sphere a rigid body and collision. I am assuming that you know the cloth and rigid body settings, as I am not going to go over that.

Then, you would subdivide the plane as many times as the quality that you need/want.

For the next step, you would need to place the UV Sphere directly over the plane. Then, you can change the mass of the UV Sphere in the Rigid Body Simulation, and then when you play your animation using Alt-A or the Play Animation button, then the plane will deform accordingly.

Then, select the plane and the UV Sphere with Shift-Right-Click, press Alt-D, and then place them wherever you want the second DIFFERENT set to be. Next, in the Rigid Body Simulation tab, just change the mass accordingly.

Hope this helps!!!

Note: If this doesn't work, then remove the Rigid Body Simulation, keep the Colision though, and insert keyframes on the start and end of where you want the UV Sphere(s) to start/end.

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  • $\begingroup$ I have failed to recreate the expected behaviour by following your first three paragraphs. My sphere falls through the cloth and isn't stopped regardless of the spheres weight. Could you post a minimal working example (blend file on blend-exchange) or upload a gif of what the result looks like. $\endgroup$
    – Leander
    Commented Sep 27, 2018 at 17:03
  • $\begingroup$ Leander, that's actually what I mentioned in the 'Note:' section. This may happen, and so just remove the Rigid Body Simulation, keep the Colision though, and insert keyframes on the start and end of where you want the UV Sphere(s) to start/end. $\endgroup$
    – user61976
    Commented Sep 27, 2018 at 21:39
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    $\begingroup$ The question is asking for a way to simulate the impact of two spheres. A handmade keyframing animation, does not seem to be fitting. $\endgroup$
    – Leander
    Commented Sep 27, 2018 at 21:44
  • $\begingroup$ It still works perfectly though, and provides a solution to the above question. $\endgroup$
    – user61976
    Commented Sep 27, 2018 at 21:55
  • $\begingroup$ You only have to insert 2 keyframes, one where the Sphere is above the cloth, and the other where it is below. I have tried this; it works. $\endgroup$
    – user61976
    Commented Sep 28, 2018 at 11:29

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