topic Re: randomized rigid bodies in 3ds Max Forum

randomized rigid bodies

Anonymous — Sun, 12 Jul 2020 07:00:25 GMT

I am trying to create rigid body sticks in randomized positions. I have written a script that creates many cylinders in randomized positions. I then use Massfx to make them dynamic bodies to run a simulation for gravity. However, when the cylinders are first created, they are not rigid bodies and since their positions are randomized, they may go through each other, which is not something I want. How would I be able to create many rigid bodies in randomized positions?

Re: randomized rigid bodies

Anonymous — Mon, 13 Jul 2020 09:06:06 GMT

How about using mParticles instead? Something similar to this simple setup?

(Attached the scene file in 2020 format.)

Re: randomized rigid bodies

BenBisares — Tue, 14 Jul 2020 03:18:52 GMT

With that workflow there will always be the risk of intersection since the placement is done before the collision detection. For example if you wanted a pile of sticks on the floor I would try the following:

Using either your script or something like the Array tool to first place the sticks in a position where they are not touching each other and high up in the air
Create a "catch" object like a plane
Set up your rigid bodies
Simulate and have the sticks fall to the floor, stop when your satisfied with the results
Use the current position as the starting point for your next simulation

Re: randomized rigid bodies

BenBisares — Tue, 14 Jul 2020 03:22:32 GMT

@Anonymous workflow could also work depending on the complexity of your objects.

Re: randomized rigid bodies

Anonymous — Fri, 17 Jul 2020 21:23:30 GMT

Thank you for the reply! I am testing out mParticles right now. Is there a way for me to designate how many particles there are? For example, sometimes I might want 20 sticks falling, in another simulation I might want 500 sticks falling.

Re: randomized rigid bodies

Anonymous — Fri, 17 Jul 2020 21:50:24 GMT

Actually, I was able to figure out how to adjust number of sticks. I do have one more question, though. When the sticks fall on the ground, they seem to bounce around a lot. Is there a way to prevent this?

Re: randomized rigid bodies

Anonymous — Sat, 18 Jul 2020 00:32:22 GMT

Additionally, one last question. My particles are quite "fine", as in, their dimensions are 0.05 radius x 20 height. However, I need them to pile up quite high (about fifty times the height). This means I need many sticks. You can think of it as a sand pile except instead of sand, it is very fine rods. When I try to set the number higher (ie 2000) I exceed safe mode calculation. How can I prevent this and generate a pile?

Re: randomized rigid bodies

Anonymous — Mon, 20 Jul 2020 16:34:23 GMT

Fine structures like that can really bring down the mParticles. Engine. For example i can simulate a 0,5 x 20 cylinder up to 3000 particles just fine, but with 0,05 x 20 pieces it grinds to a halt.

You can turn off Safe Simulation Mode in the MpWorld->Advanced Parameter rollout or increase the Calculation Limit.

Re: randomized rigid bodies

Anonymous — Wed, 22 Jul 2020 20:29:21 GMT

I see, thank you. I was wondering, is there a way to make sure the particles come out at a slower rate? For example, if I set the particle number to 3000, have the particles come out so it doesn't seem as if they are all spilling out at once?

Re: randomized rigid bodies

Anonymous — Wed, 22 Jul 2020 22:18:13 GMT

Also, is there a way to have multiple mParticles simulations one after the other without resetting? For example, after I finish one mParticles simulation, I want the sticks to remain in their end position and then run another mParticles simulation on top of the old one (this way I might be able to bypass the maximum number of particles).

Re: randomized rigid bodies

Anonymous — Thu, 23 Jul 2020 02:49:30 GMT

i tried to take sections (cross sections using the shape modifier) of the mparticles but I realized that they don't show up. What can I do to take cross sections of the end product?

Re: randomized rigid bodies

Anonymous — Thu, 23 Jul 2020 03:10:14 GMT

I have attached a screencast for your reference. The blue cylinders are the particles. You can see that there is a pink outline on the side and that is because I tried to take a cross-section but only the outside green tube is affected. The mParticles are not affected.