PDA

View Full Version : Fracture - does it only work on convex models?



DiscoBurgess
04-18-2012, 04:31 AM
I'm trying to fracture a bridge that is, I'm certain, all closed up and watertight, but I keep getting a few spiky polygon rays that spread out and pass through other arches of the bridge.

I'm wondering if I've missed something on my model, or if it's a limitation of Fracture.

It's no problem, happy to break the model up a bit and fracture individual sections, but it would be good to know if I need to do this, or if I need to get better at checking my model!

JamesCurtis
04-18-2012, 07:33 AM
Did you make it all tri poly? Its noted in the docs that tri's are preferable for better results.

DrStrik9
04-18-2012, 08:51 AM
I've had that happen too. Changing Fracture's Random Seed sometimes helps. But like other geometry, I usually just follow the oddities with Select Connected to see if they can be deleted. And of course look in Poly Stats to make sure there are no 2-pointers, etc. -- Don't merge points in Modeler though. :)

DrStrik9
04-19-2012, 01:36 PM
Did you make it all tri poly? Its noted in the docs that tri's are preferable for better results.

Tripling before Fracturing doesn't seem to help this problem. I'm also getting "non-closed" sub-objects with Fracture, and 10-12 of these "pointy polys" that extend beyond the originating object, with 180 Cell Count. Attempting to fix the error-filled Fractured (tripled) geometry is not my idea of fun either.

Think I might send in a bug report on this ...

djwaterman
04-20-2012, 07:37 AM
Mind if I hijack the thread with another fracture question, does V11 do secondary fracture, as in the main object is fractured and collapsing, and the the fractured parts break once more as they hit the ground or self collide? I watched someone doing this in Max today so I'm curious.

dee
04-20-2012, 08:11 AM
Mind if I hijack the thread with another fracture question, does V11 do secondary fracture, as in the main object is fractured and collapsing, and the the fractured parts break once more as they hit the ground or self collide? I watched someone doing this in Max today so I'm curious.

Something like this? Just play with Glue Strength/Breaking Angle/Breaking Distance.

imshadi
04-20-2012, 06:23 PM
I experienced the same thing. It seems to me that the fracture routine is forgetting to triple things after each iteration or it also may be forgetting to merge points. The little shards and the missing polys I was able to clean up by hand. But it may get cumbersome on an object with too many breaks. I suggested this to Mike Green who also has some Fracture Scripts, including a Voronoi one, but which also failed for the same reason. I hope some one will fix this soon enough.

djwaterman
04-20-2012, 10:29 PM
Something like this? Just play with Glue Strength/Breaking Angle/Breaking Distance.

I shouldn't have hijacked the thread, sorry. I see what you are doing but that's not really what I mean, After the first breakage, pieces break away and continue to fracture into smaller bits as they either hit the ground or collide with other pieces. It bogs down the calculation but looks more realistic.

Greenlaw
04-21-2012, 12:41 PM
Like this? (Wait for the second example at around 0:23)

Lightwave 11 - Fun With Glue (http://bit.ly/JX7xEh)

IMO, calc time is actually quite fast.

BTW, you can also vary the breaking sensitivity using envelopes and textures. I didn't use it in this example but it can give you a lot of control.

G.

djwaterman
04-21-2012, 08:26 PM
That looks better, I followed some of the pieces as they fell and hit the ground, breaking, and then another bit breaks off as it falls over and hits a second time. I should really fool around with this stuff myself to see what it can do. I'm still not sure if that's exactly like the simulation in Max.

DrStrik9
04-23-2012, 10:09 AM
Unfortunately, Fracture has several problems. I've identified several ways already that can either produce unfixable results, or send Modeler into hyperspace on Mac (needing to be force quit). I had a Fog-Bugz party over here all by myself. :D Once it's fixed, Fracture will be an extremely valuable tool for Bullet -- withOUT all the manual clean-up and bombing.

Glue Strength is indeed a FUN toy. I've been doing sims with 99.5%+ Glue Strength and only a .001% or .002% difference between previews, and getting very interesting results. The closer you get to 100% with Breaking Angle and Breaking Distance turned off, the cooler Glue Strength is.

Netvudu
04-24-2012, 08:40 AM
Geometry mass has quite a dramatic effect on Glue Strength though. You could probably play with much more comfortable values than .001 or .002 by altering the object┤s mass...

...then again, you seem to enjoy it so you can disregard my hint... :D

Greenlaw
04-24-2012, 09:14 AM
...then again, you seem to enjoy it so you can disregard my hint... :D
Thanks for the tip! Sorry, but I'm not going to disregard that. :)

G.

Dreamer
04-24-2012, 09:22 AM
I posted this in another thread, but this seems the better place. Glue is great for keeping a body intact while causing it to move nicely.

silviotoledo
04-25-2012, 05:13 PM
Great Puppet!

How much percent Glued you used?

May you share your scene?

Greenlaw
04-26-2012, 02:25 AM
Here's a simple but useful Fracture trick I figured out the other day:

Controlling the Fracture Tool (http://bit.ly/I2mcPF)

G.

Greenlaw
04-26-2012, 02:28 AM
I posted this in another thread, but this seems the better place. Glue is great for keeping a body intact while causing it to move nicely.
That's very clever!

G.

Dreamer
04-26-2012, 06:31 AM
Thank you. I used 100% glue and 270║. The degree number seems to be the most important for something like this.

Dreamer
04-26-2012, 08:10 AM
Here's a simple but useful Fracture trick I figured out the other day:

Controlling the Fracture Tool (http://bit.ly/I2mcPF)

G.

That is very nice. How did you come up with that?

Shiny_Mike
04-27-2012, 03:58 AM
Placing different sized spheres in the background layer and using the "background layer polys" works nicely too, with the added benefit of being able to control the cell count. Little more tedious to setup but I've been happy with the results. :thumbsup:





Here's a simple but useful Fracture trick I figured out the other day:

Controlling the Fracture Tool (http://bit.ly/I2mcPF)

G.

imshadi
05-02-2012, 06:55 PM
I've used DMM on Maya. At least up to the version I uses, the shattering is not really interactive. The object is initially fractured using Voronoi, and a "resolution" which means the higher the number the finer the pieces that can break. The object, however, stays together in one piece and breaks after enough force has been applied. All this in a manner that did not feel that different to that which LW's Bullet does, only in LW you have to break the object by yourself. After that setup time in LW is almost zero (and Sim time is darn fast, Real Time for most simple cases!).

Even my friends from the Blender world are impressed by the simplicity of the implementation of Bullet in LW, which I can also only applaud. I just hope the add some more production features in the future, because right now it feels like a feature in introductory mode. Amazing and beautiful, but when you do complicated things, immediately you start needing it to be more flexible, like being able to interact with MDD cached objects, separating pieces as new baked elements, etc.

On the other hand, I have seen Rayfire's method of breaking secondary pieces and of breaking pieces in clusters. That and it's many fracturing algorithms is what really makes it stand out.

Some examples of Rayfire here: http://www.youtube.com/watch?v=u_2qKQpxCRw

I think what looks artificial about Voronoi Shattering and Halves Fracturing is the fact that most of the pieces that break off have similar sizes, while in reality there is a very clear abundance of smaller bits over larger chunks, with a probability that is dictated simply by Bell's curve. If you don't have then a similar distribution of pieces in your simulation, keen eyes and some not very keen can immediately tell there is something fishy about your broken object.

If LW's programmers decided to incorporate the Bell Curve in as many things as possible, every effect LW does would look a lot more impressive. From the concentration of light in a volume coming out of a Spot Light, to a particle emitter, to fracture algorithms. All of these things in LW tend to behave in linear like manners, resulting in only mediocre effects and cumbersome workarounds. I wish I could ***** slap some Newtek programmer into doing these things... or at least beg them to do so! They did great with LW11 I just hope they keep up the spirit of reconsidering and fixing everything...