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I created two tubes by Bezier curves and add sodify modifier to them with a small thickness. And add rigid body and collision to the tubes. I check the normals, upscale the steps per second and iteration number, set sensitivity margin to 0, but they still overlap. And when they hit each other, they rotate together.

I hope someone may give me some advice. Thank you.

enter image description here

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  • $\begingroup$ Hi Vklidu, yes, I have changed the type to be convex hull, and set margin as small as possible but larger than 0. It seems work. When I have more objects, however, the objects on top will be floating not touching the bottom objects... $\endgroup$
    – tryphena
    Commented Apr 16, 2021 at 14:20
  • $\begingroup$ I am using microscale. I am not sure if that causes the problem. Please check the file in the link. Thank you. blend-exchange.com/b/7Xk4kxSY $\endgroup$
    – tryphena
    Commented Apr 16, 2021 at 19:56
  • $\begingroup$ Specifically in your case just delete all innert geometry and use Solidify modifier. Also there is not a need to use Collision modifier that is aimed to be for Cloth a nd Particles sims. $\endgroup$
    – vklidu
    Commented Apr 18, 2021 at 12:13

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Don't set Margin to zero, use as much as you can (to result with good looking sim). To simulate thick objects is always problem. Low margin value increase possibility of objects penetration (like that you see with your setup - they hook each other and rotate as crazy).

enter image description here

Anyway ... Margin didn't solve the issue here. Result was hysteric as in your case.

I had to start with defaults.

In this example - add Curve object, set Depth, Convert to Mesh, add Rigid Body / Active / Shape>Mesh / Margine 0.01, add Solidify modifier (Thickness 0.02) ... copy object few times and run sim.

What definitely helped here ... use tubes thickness as modifier not as real geometry.

Solidify modifier > Thickness 0.02 enter image description here Note: Margin 0.01 is from some angle view visible so you can use also 0.001, but sim can became jumpy.

General rules for successful sim - Apply Scale, Origin to Geometry (it is not your case).

So the issue is caused by inner faces of a tube (when real geometry). That is weird for me since margin is low so there is not even a possibility collision margin crossing from inside tube through to outside (to create effect like switched Normal direction). So I don't have an explanation for that.

Increasing Solidify modifier Thickness to 0.06 and Apply Modifiers make the sim possible.

Solidify modifier > Thickness 0.06 ... Apply modifier (make real geometry) enter image description here Note: In a middle of anim it exploded because of collision penetration so I enabled Margin for floor object 0.04 that make it stabilised.

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  • $\begingroup$ Hi Vklidu, thank you very much for your hard work to figure my problem out. However, I still could not reproduce your result. The file you uploaded have some setting missing. I add collisions to the tubes and the plane, and set substeps for frame as 120 and iteration number as 60, and the tubes fall without penetration. I have been able to remake a tube in your file and fall as expected. $\endgroup$
    – tryphena
    Commented Apr 19, 2021 at 14:23
  • $\begingroup$ And I have found that I shall not click the "apply" in the solidify modifier. In your file, if I click "apply" in the solidify modifier, the tubes will penetrate each other..But in my another computer, I start the same process to build the tubes, they just hit and fly away..I have tried add rigid body/collision before solidify and add solidify before rigid body/collision. no luck $\endgroup$
    – tryphena
    Commented Apr 19, 2021 at 14:23
  • $\begingroup$ Don't use comments for "chatting". Please delete comments and try to summarise your actual thoughts into one simple comment ... or even better "edit" your OP (original post) if you have more info about the issue. Thank you ... BTW I used 2.93 and worked in 2.92 as well for me. If answer solved your issue consider mark as accepted blender.stackexchange.com/tour Thank you keep site useful :) $\endgroup$
    – vklidu
    Commented Apr 19, 2021 at 19:16
  • $\begingroup$ very nice to have your instructions and help. Thank you! $\endgroup$
    – tryphena
    Commented Apr 28, 2021 at 14:18

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