Massfx Question

[Anonymous]

Good Morning. I am having a bit of trouble utilizing Massfx in my current workflow. I have an excavator that is digging a shallow trench in the ground. I have rigged up a whole mess of dirt fragments to be dynamic objects starting in sleep mode, and the bucket to be a kinematic object meant to dig them up. However, as illustrated in the attached images, when the bucket touches the first object, the entire trench explodes. I've monkeyed with their bounding boxes, density, initial speed, bounciness, everything I can think of. Anybody have any ideas on how to fix this?

[Anonymous]

Hello Aurora. I'm guessing that you're going after a more "these guys should clump" kinda behavior (as it would be in real life).
In real life, a bunch of chunks like the ones you have there would indeed progressively move because of the compression and damage that they would sustain. Also, some chunks would dig deeper into the ground instead of going up, and lastly, a lot depends on the size of the chunks after them. This results in chunks moving "progressively", instead of all at the same time.
In MassFX, objects cannot compress or sustain damage like that, since they are "infinitely" rigid. Since the object cannot do this, it has to disturb the other chunks around him, and they move, disturbing the surrounding ones, and this goes on and on.

I can think of a couple of ways of working around this. First, from the images you posted, it seems all chunks are roughly the same size, in average. You could try inserting some bigger objects here and there that would have greater mass, and therefore, would be more difficult to move by its neighbors, and see if that makes a difference.

Alternatively, you can completely fake this using the Kinematic to Dynamic switching functionality in Rigid Bodies. What you'd need to do is select the objects closer to the initial point of impact of your machine, and leave those as dynamic. The rest of your chunks should be kinematic. Now, select some of the chunks surrounding the dynamic ones, and set them to become dynamic at a frame number where it seems the dynamic ones will make contact with them (using the "Until Frame" checkbox below the Rigid Body Type dropdown). Keep doing this selecting objects further away each time, and making them become dynamic at later frames. This should give you some sort of gradual radius (in any direction you wish) of objects that become dynamic at later frames, simulating the behavior you are looking for.

I've attached a VERY SIMPLE sample file of how you'd achieve this. I've color coded my objects according to when they "wake up" (not using the "sleep" parameter, but the Kinematic To Dynamic switching time). This should give you a better idea of how to do this, in case my explanation was too convoluted. The file is from Max 2013, and I don't have any other version installed right now, so I hope you can open it.

I hope this helps. Cheers!

[Anonymous]

That seems like you may have hit the nail on the head there, but it appears that your example file didn't quite attach. Would you be able to reupload it? I think I understand the thrust of what you are getting at, but seeing it would be incredibly helpful. And, just in case, would it be possible to save it as a 2012 version? The massfx stuff should transfer over fine, I'm just using 2012. If you change the file type when going save as, there is a list of .max types for different versions, if it's not too much trouble. Thank you for your help!

[Anonymous]

For the life of me, I can't attach a file to my reply. Try this link...

https://www.dropbox.com/s/4g9pmvbocin7qc0/MassFX_gradualWakeUp_2012.rar

Just let me know when you've downloaded it, so I can remove the file. I hope this helps!

[Anonymous]

All downloaded, thank you! The attachment issue might have been from it being a .rar, I've found the only non-image files it will let me attach on this board are .zip files, did you try those? Thank you for the example, I'll look over it the moment I get a chance! Cheers!

[Anonymous]

Ah, I see... I was trying to to attach the MAX file first, and then a RAR file... I guess that's the problem.
Anyway, I hope that sample helps. I deleted all the MassFX modifiers from the objects to save some file space, but I think you'd get the idea... let me know if you want me to re-send the file with the modifiers on the objects (now that I think of it, the RAR compression would've kept the size reasonable anyway...)
Cheers!

[Anonymous]

Hmm, that`s a very clever approach! Still getting into the swing of things with massfx, reactor, I shall miss you. I think I understand what you did with the timing there, a few baking passes and the like, and everything happens sequentially. A few clever selection sets and modifiers will hopefully help resolve this problem lickity split. Thank you for your help!

[RobinBall6995]

Rayfire is very good at handling this sort of thing. If you plan to do a lot of this type of destruction it's well worth it.

[Anonymous]

Yeah, I've played with Rayfire, but I only need this sort of thing occasionally, just some way to rig up a digging of a trench. For these fragments I used the Fracture Voronoi Script off Scriptspot to bust it up, that's why most of the fragments are similar size.

[RobinBall6995]

I have problem with MassFX that might be the same here.

The default collision type is Surface. There's another type called Vertices. If I use Surface, then the collision hulls are pushed slightly bigger than the actual geometry. That makes them overlap and therefore immediately fly apart when I sim a scene.

This push is a fixed value of 0.01. Which means if you're using metres as system units, it's actually quite a big distance.

So pick one of your fragments, zoom in and see if the collision hull is bigger than the geometry. If it is, select them all and set their collision type to Vertices. You can use the MassFX tool window to do this on them all at once.

However. Rayfire wakes up objects only when they're actually touched by another moving object. MassFX wakes up all touching fragments as Toonman says. That means it's more likely the whole lot will wake at once. So they might still all fall down at once. You might be able to prevent this by adding a push modifier on all the fragments and push them in a little to make gaps, then run the sim, then once it's baked, delete the push modifier.

Hope some of that helps.

[Anonymous]

I am sorry for answering a post where it doesn't belong. I need some help quickly on a particle flow and really don't know where to turn and how to find the right forum to post this. Please help. I'm on 3ds Max Entertainment creatin suite 2014 and have a PFlow question. Pleas direct me to the correct forum so I can post a question to solve my problem. Thank you so much if you decide to help me. Or at least send me in the right direction. I need someones help on duplicating a particle flow. Thank you. Thank you.

[Anonymous]

I'm new to this forum but I should have been on it for years. Sorry. I have a specific question. I have a particle flow setup. The scene shows a pipeline and a valve. The gas pressure pushes rust and debris down the pipeline that collides with a ball on a large ball valve. I have the PF setup and you can see the particles blow into the frame and bounces off the ball as it is closed and the particles come to rest at the bottom of the pipe. Now I copy the three pflow events and then suddenly the deflectors pass completely different information on to the next event. I can't figure out why. It must be something simple that I'm missing. I can post a sample if someone can help me. Please. Thanks in advance.