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TheGreenGiant
10-14-2003, 12:37 PM
Hello there,

I'm trying to get my set to basically shatter and break away in chunks and consequently fall down. As is, I'm using the constructed polyset, activating the shatter solid effect but its impossible to work with dynamics (too many penetration problem) once the thing starts to fall apart - tried like the help suggested to make the shapes not detect collision (initial state) and then keyframed collision back on after the pieces have moved away a touch; still no good. Crazy collision problems and maya crashes.

What should I do now? Completely remodel my set to provide provisions for destructions? Can someone link me to a tutorial on how to make this work?

WhiteRabbitObj
10-14-2003, 04:03 PM
What do you need collisions for? Is this a simulation or just an effect? If the set is exploding, then fire can cover up a lot. If not, you can change the collision detection type to "Mid-Point" instead of the default "Runge-Kutta Adaptive", this will be much faster though less accurate. If you post what the point of your scene falling apart is it may be easier to help you design the effect. Solid Shatter effect is incredibly cool but it certainly creates some insane geometry that you're really just never going to simulate colliding unless you have days to let it compute, which is impractical for most people. Gives me new respect for that asteroid breaking up shot in Ep2!

zachgrachan
10-14-2003, 04:54 PM
woud a surface shatter work? it's a lot less geometery, and it has extrude options to give thickness to the chunks. Some particle instancing could make up the difference in debris.

TheGreenGiant
10-14-2003, 07:11 PM
wow. quick feedback. Thanks guys.

Lemme get an image so you guys know what I'm talking about...

I'm not looking for an explosion shot, the animation should look like something shakes the structure with such force that it breaks apart (implodes) and falls down in chunks.. Kind of like how the twin towers fells or maybe a demolition job. Not excessively breaking apart though.. more like a structural collapse. A reference I can think of is the shot of the houses in sunnydale collapse as buffy escapes (but in closeup and we'll get to see detail) Guy at school here suggested shatter + fields (in like a 2 minute tut) Grrr... doesn't really work and my animation is stuffed if I can't get this thing sorted.

I I thought I would need collision for this to work as the chunks/shards would have to land and stop on the floor (Passive Rigid Body). Keyframing is not possible/an option, no?

* asteroid breaking up shot in ep2? Don't remember it but is it the space flight sequence?

http://www.redrival.com/TheGreenGiant/01.jpg

Back on topic. The image obviously doesn't show post demolition rubble but I need to get the set to break down and crumble in chunks. Its not a brick structure and I'm happy for it to shatter/have sharp edges.

TheGreenGiant
10-14-2003, 07:27 PM
Here's an external shot.

http://www.redrival.com/TheGreenGiant/02.jpg

zachgrachan
10-14-2003, 08:00 PM
alright, more details are better!

I would probably go with shattering the parts(though if time was available, I'd do it by hand cuz I don't like giving up all that control) - and then using collisions.

To go into more depth. Start by turning all the shards into active rigid bodies, turn the ground/floor into passive rigid. Then go into the passive body's attr editor, and change collision layer to -1, that makes it collide on every layer. Then go through all the active rigids and set them to different collision layers. layer 1 will only collide with 1 and -1, layer 2 will only collide with 2 and -1, etc.

To calculate all those chunks(with rigid body's quantity SEVERELY affects calculation time) you may need to turn off Is Dynamic for groups so that they are ignored, rendering out pillar by pillar for instance. Then composite all the parts back together.

Oh, and definitely - DEFINITELY - use stand-ins(low res primitives) for any shards you can.

TheGreenGiant
10-14-2003, 08:41 PM
Originally posted by zachgrachan
alright, more details are better!

I would probably go with shattering the parts(though if time was available, I'd do it by hand cuz I don't like giving up all that control) - and then using collisions.

To go into more depth. Start by turning all the shards into active rigid bodies, turn the ground/floor into passive rigid. Then go into the passive body's attr editor, and change collision layer to -1, that makes it collide on every layer. Then go through all the active rigids and set them to different collision layers. layer 1 will only collide with 1 and -1, layer 2 will only collide with 2 and -1, etc.

To calculate all those chunks(with rigid body's quantity SEVERELY affects calculation time) you may need to turn off Is Dynamic for groups so that they are ignored, rendering out pillar by pillar for instance. Then composite all the parts back together.

Oh, and definitely - DEFINITELY - use stand-ins(low res primitives) for any shards you can.

Mucho Gracias. It's 4.35 in the morning here and I'm close to collapse and vomitting all over the computer here.

Questions; there are always questions :D

a) How do you shatter by hand? Draw spilt? Cut face? I couldn't work out how to do a manual split and still have look that shatter can give a model.

I understand the collision level layer just fine I think. I guess it's diving in and getting the settings set out for a test sequence. I didn't know about collision layers solution though. AWESOME. That is a TOP tip!

b) you mentioned turning off the dynamics for group? Where's that option? That sentence reads a bit funny and I'm not sure what you mean. Please explain. I wonder how intensive the dynamics calculation for the scene will be - should I just let the simulation run and then bake it in? Would that be better or is the composite solution the better option - I'm concerned that composite aside, that shards will overlay one another as they're not calculated to collide (as is) But then, I'm also guessing that the fact that it is rubble kind of justifies the collision/interpentration.

Got the message about the stand-in shards loud and clear.

:thumbsup:

WhiteRabbitObj
10-14-2003, 10:42 PM
Here is what I would do, since you seem to have drawn and suggested there will be dust. Make stand in's for each shard, as simple as a sphere or cube if you can get away with it. Make THOSE collide with each other and the floor, have your dust effects swirling around yadda yadda covering up some of the interpenetration. As they hit the ground, a larger dust cloud likely billows up, judging from your illustration. Take this opportunity to hide the rigid bodies and make visible non-rigid copies that you position to not penetrate the floor or each other and you can make the end result look as pretty as you want. If this isn't for a commercial project, which I don't gather it is, then you have to be forgiven for cheating what you can, because the calculations are just too intense. I also didn't understand the thing about "turning off Is Dynamic for the group" but as for manually shattering you can draw new edges with the split edge tool, then use Extract to separate whatever faces you want from the whole polygon object and voila, you have a new piece. Do this until you have the pieces you want. you'll obviously have to fill any holes, preferably not with "fill hole" but instead by using extrude edge a couple times, then merging the vertices, and then you can adjust the new edges to make it look like a chunk that shattered off.

Good luck.

zachgrachan
10-14-2003, 11:08 PM
maybe I was thinking of particles on the Is Dynamic thing, I'll check soon as my render finishes and my box can handle maya again...

Basically what it does is turns off that node, before wasting time calculating. So if your environment has particles going in the BG, you don't have to run them as you work on the character or whatever. I know particles have it, and I thought rigid did too, but I'll let you know...

As WhiteRabbit said, manually shattering is just cutting and extracting faces, I prefer this because I don't like to shatter over and over looking for just the right look. I like control over every aspect of it, so I do it by hand - if I have the time. It also can save a lot of geometry, shatter can get pretty heavy on a complex model.

Just a lot of tweaking to get it to look random, but caused by a specific force.

TheGreenGiant
10-15-2003, 10:37 AM
hey guys, thanks for the advice. I'm going to go ahead and follow this (guess I have to do the poly split thing after all. I was so hoping it wouldn't have to come down to this :( Long nights of poly splitting ahead. :D



:beer:

zachgrachan
10-15-2003, 11:02 PM
good luck!

better go get some coffee, lots of coffee

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