Ok, I have an incredibly simple cloth simulation in which I have a subdivided plane with cloth physics, and a regular plane (bigger than the first) with collision physics on it. The cloth is above the ground plane. I can hit Alt+A, and the cloth will usually fall down onto the ground plane. nice and easy, like I want it. Sometimes it doesn’t. And when it does, sometimes it’ll stop working if I change anything in my scene.
So I’m frustrated. I want the cloth to be able to behave dynamically in preview mode (Alt+A) and update the behavior when I add collision objects, scale the cloth, or whatever so that when I hit Alt+A again it will behave like it’s supposed to.
Additionally, I’d like to place another collision object above the cloth to fall onto the cloth, but that wasn’t working when I tried it earlier. (That’s when I reverted to troubleshooting with a simple setup.)
That’s my problem and my desired result, but I have no idea how to make it happen. I understand that it probably has something to do with the cache or baking, but I don’t yet know enough about Blender or the placement of certain options to control the cache at my whim (or if it’s even possible). Can anyone point me in the right direction?
I’m using Blender 2.68a on Window 7 Pro 64bit, 12Gb of RAM, 3.07GHz quad core i7, NVidia Quadro 4000 video card. Also, I’m in “Blender Render” mode.
Moved from “General Forums > Blender and CG Discussions” to “Support > Particles and Physics Simulations”
Thanks for the re-direction!
I’ve sorta noticed this issue, and I think it’s related to where you are on the timeline. So make sure you are at frame 0 before hitting Alt+A.
As for your object falling on top of the cloth: either a ) use rigid body dynamics to let the object be affected by gravity, or b ) animate the object to move down the z-axis. In both cases you need to add a collision modifier to the falling object, rigid body will be more realistic, but can tear the cloth appart, animating will be less realistic, but at the least it won’t tear the cloth.
Never tried making the cloth part of the rigid body sim, dunno if those two sim-systems fight all that much.
- You can’t just throw things at a simulation. If you make changes, you need to re-bake it.
- If you do change objects by scaling and/or rotating them in Object Mode, you need to apply those changes with Ctrl-A before using them in the simulation
- Collision physics won’t make an object fall. You need Rigid Bodies for that. You can use both on a single object though.
Edit: Therahedwig beat me to it, but I can confirm after a couple quick tests that Rigid Bodies and cloth seem to get along pretty well. You just have to set your Rigid body object to also be Collision objects, and your cloth as an active Rigid Body. Don’t check “Animated.” You may have to play with margins and shape settings.
I appreciate the advice. I applied it and made my cloth and falling object “Collision” and “Rigid Bodies.” I had to keep my ground plane just “Collision” or it fell too.
The cloth behaved nicely, but the falling object fell right through the ground plane and dragged the cloth with it, creating a bunch of undesirable spikes in the cloth.
And I can’t seem to find (or remember) where the controls are for how close an object needs to be before it interacts.
I’m sorry for the basic questions, but I am new, and I really appreciate your patience.
Not sure if my reply went through properly, so I’ll attempt to say it again…
Thanks for the advice! I put most of it to use, and applied the collision and rigid body modifiers to the cloth and falling object. However, the falling object fell right through the ground plane (now a large cube, collision only), and pulled the cloth with it.
Also, no matter where I put the play head (I make a habit of puting it at “0” now) it’s still a toss-up whether the physics will play correctly the next time i press ALT+A…
Oh. Well, there’s my other post… I guess I underestimated the moderation period.
I really need help here… I’ve simplified the scene to a large cube with Collision, and the falling mesh with collision and rigid body.
The falling mesh passes right through the cube, and I can’t get it to stop when it hits the cube.
Try making the ground plane a ‘passive’ rigid body object. That should prevent it from moving.
Edit: Don’t worry, I think on avarage everyone sometimes tries the physics sims for fun, but I have the feeling only a handful of Blender users can claim not to be newbies in that area. There’s very little tutorials on complex scenes for example, and rigid bodies have some lack of workflow info on them in general, being very recently introduced.
Thanks, Therahedwig! that helps a lot! Unfortunately, this isn’t for fun, this is for work. My director know I dabble in Blender, and I said that this relatively simple concept shouldn’t take very long to mock up. Ha.
Now it’s looking better, but it’s got a ways to go. When it hits the ground plane, it either bounces like crazy when one or both are set to “Box” shape, spins crazily as it falls right through the ground plane when both are set to mesh, and when both are set to UV Hull, it still bounces and even dips down into the ground plane a bit.
Bounciness settings are both at 0, and it still bounces quite a bit, no matter what I do. I want it to bounce less, but I cant go any lower!
Recent feature or not, why is it so difficult to get one mesh to fall and land solidly on another mesh?? What am I missing?
Yeah, sorry I didn’t make that clear. To make something fall, it needs to be a rigid body. To make anything else interact with it, all those other things also need to be rigid bodies. If a rigid body object is just going to sit perfectly still and never be disturbed while other stuff bounces off it, make it passive. For all other uses, make it active.
So, to itemize that:
- Ground/floor plane: Collision and Passive Rigid Body
- Cloth: Cloth (probably with self-collision on) and Active Rigid Body
- Falling Thingy: Collision and Active Rigid Body
Edit: “it bounces like crazy” you say? What is “it”? The cloth or the falling box? If it’s the cloth you might try tweaking the Air damping setting so it doesn’t catch a big cushion of air beneath it.
At this point you might just be best to post your .blend file. Use www.pasteall.org.
I think he means the object, in which case their should be an option in the collision settings that should determine how bouncy a rigid body is.(you can find this under the particle tab)
Yeah, the systems don’t always make sense together, and that’s because they use wildly different calculations and were otherwise not designed as one full whole. I’m not sure whether particle-node guy becoming part of BF means this is going to change sometime in the 2.x series, but iirc correctly, Ton did mention wanting to allow big changes in 2.7 and 2.8, and if my mind doesn’t betray me, he uses a generic reference to the simulation systems as example.
Edit:derp, I only just read you said bounciness is set to 0… hmz.
You are all awesome. It helps a great deal. Thank you.
Due to workplace network restrictions, pasteall.org is blocked for me.
The falling thing is my company’s logo. I created it in Blender using vector curves, extruded it, then converted it to a mesh.
Eventually, I want the logo to fall past the camera and lay flat on some cloth (like a tablecloth or something) so we get a little bit of ripple effect on the cloth, with minimal bounce. I’d have to tweak those settings to get it to look right, but that’s the look I’m after.
Particle settings for a falling object? odd…
I looked and can’t find any collision or bounce setting in the particle tab (even after I hit the “+” to create a particle system).
And the particles bounce long after the logo stops bouncing. Well, I’m off work for the day. I hope someone can mull this one over so I can pick up and learn tomorrow! Thanks again!
I think I better defined the improper behavior, even if I don’t know why, or really how to fix it.
The logo is a collision/active rigid body with an incredible amount of vertices. (That’s just how the mesh was created from the curves.) The logo bounced when it hit a collision/passive rigid body (the ground plane/box).
Then I tried to simplify it further by just making a falling box with collision/active rigid body, and it behaved just fine. So I joined my logo to the top of the falling box, and again, it behaved just fine. This lead me to believe that it was the number of vertices interacting with the ground plane.
So I added my cloth plane with collision on top of the ground plane. I decided to try to make the cloth an active rigid body to see if it would interact better with the falling object. The result was that the cloth became stiff and bounced like crazy. When the falling object hit it, they both bounced like crazy.
I disabled rigid body on the cloth, and it all behaved like normal cloth and solid objects.
So, I think that the number of vertices of a rigid body interacting with other rigid bodies makes it behave oddly. No idea why, but there it is.
Anyone else been able to play with it?
OK, so I’ve got the animation to behave the way it needs to. The falling object causes ripples in the cloth, but those ripples keep intersecting the ground plane and object.
Troubleshoot_002.blend (3.04 MB)
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I succeeded in make objects to collide, assigning to the cloth a rigid body passive instead of the collision modifier, but I must say the rigid body sim is a mess, not finished thing: every time you have to clear caches you have to delete the rigid body world and remake every physic assignment (AFAIK), that is for each change you make you have to restart from scratch… I had to give up.
The fact was that the cloth either penetrate other object or make it bounce as crazy, or both.
I looks like a matter of finding the right values for margins.
if I can get something then I’ll post the file.
OK, I’m posting what I’ve got so far though it’s not good at all.
I stopped all when I realized I was getting different results even with the same parameters…:eek:
Troubleshoot_002-2.blend (1.03 MB) (I had to empty the caches to eliminate 11 MB)
FYI, I have deleted all files from my hard disk.