[Custom Build] Blender Fracture Modifier

(scorpion81) #1721

Yup, understandable. 2.8 is still some time away from being stable and feature complete in general. I still also have to fight with some issues of FM in 2.8, so that may take a while too. And i wanted to start backporting only after it works fine.

I modified the “skyscraper” example to include an Emitter plane with a particle system on it. That emits only a few particles along X axis. The Particle Instance (sphere) object at 0, 0, 0 gets a particle instance modifier which references the emitter and its first particle system, and it is set to alive particles only. This way each particle gets “equipped” with an instance of the sphere. That entire thing will also get a mesh final deforming rigidbody, so its physics shape will adapt to the sphere instances which currently exist. On the house you add a collision modifier after the FM, so it will let the particles bounce off and it will update when the house updates/collapses. This way it will look like the spheres actually bounce off the house. You also could add a collision modifier to the ground to let the spheres bounce off there, too.
Furthermore, its important the sphere is a trigger, so the altering shape of the body will affect the house by activating shards it will hit.

skyscraper2.blend (2.6 MB)

If you want to fracture a character which has pose animations or so, you might find the “Fracture Animated Mesh” Settings useful. In that example i have a couple of bones, which influence an (invisible) subdivided mesh. This mesh serves as “Guide” for the fractured mesh. In that example, just run Alt A and you will see the shards will follow the guiding mesh. Autohide and Automerge try their best there to hide the cracks between the shards. And you can trigger the shards with the sphere, as in grabbing it while the sim runs and touching the fractured mesh. Shards should fall off then.
With “Animated mesh” you need to “bind” the shards to the guide mesh once before you start the simulation.
In case you refracture with different settings, you need to rebind too.
And it is better if the guide mesh has more verts / subdivisions, so the shards can better “distribute” and do not clump on a few nearby verts only. That improves the overall shape of the deformed shard object a bit.

bendtest.blend (2.7 MB)

(wolfie138) #1722

Thanks for that. it’s a definite improvement, but the settings seem to override my Passive Vertex Group.
EDIT - ah! increasing the “Constraint limit, per Mesh Island” seems to have fixed it!
also, my Fracture Constraint Settings tab is different to yours, have i messed up an option?
i have “constraint method” instead of “Search method” etc.

(scorpion81) #1723

Ah, those small UI changes were made some time ago, just rename and a bit reorder in this case. Functionality should be the same.
And passive vertexgroup, hmm. Just tested it here with the skyscraper example, i just assigned a vgroup to the the whole mesh (in editmode) and set it as passive vertexgroup, did a refracture. now nothing happens any more regarding activation. Did you maybe forget to refracture after setting the passive vertexgroup in the FM ? By refracturing the vgroup weights will be re-transferred to the shards.
And yes, limit 0 means basically “make as many constraints as you can” inside the search radius. a limit just caps the constraint count to x constraints per shard.

(mcbeth) #1724

thank for the samples will have a look…thanks again

(wolfie138) #1725

I have noticed some of the things i’ve been fiddling w/ don’t show up until you refracture and I may well have forgotten to refracture, but i think it was just the Constraint Limit Per Mesh Island value that sorted it.

(Kai Kostack) #1726

Drag & pressure simulation prototype for Fracture Modifier


Hello all - I’m trying to bind a window to a concrete slab, using FM (& Bullet Constraints Builder for the building)

I’m trying to recreate what Kostack Studio managed to achieve here: https://www.youtube.com/watch?v=98ZfN8PutyY

:smiley: Great work, by the way!

I’ve made a quick video of a simplified model to outline the problems I’m having: https://www.youtube.com/watch?v=86RBbIMItoY&feature=youtu.be

Any help very much appreciated!


Can’t attach blend file as I’m a new memeber, but here’s a link to the blend file in G Drive: https://drive.google.com/file/d/1-dmjN1lY2VMFO_J6obnVdHjjvjTEBJIe/view

(Kai Kostack) #1729

That’s a bug, scorpion81 will try to fix it. It works when the target object has an FM applied, so you can work around this issue with the “Build FM” option in the BCB, that will create one FM object instead of many individual rigid bodies for your base structure.


Oh it’s working! :grin:

“It works when the target object has an FM applied”

This was the bit I was missing…

Thanks Kai!


Certainly getting somewhere now, however…

Slight issue with the ‘Build FM’ is the scaling afterwards as you can see in this image…

This was solvable with the regular ‘Build’ since everything is a separeate mesh, and could return the scaling to 1 rather than 0.950.

I tried pre-scaling before Build FM to 1.050 in anticipation, but then the simulation went crazy… I’m guessing because of intersections…

Any ideas?
Thanks yet again!!!

(Kai Kostack) #1732

You are right, unfortunately the Build FM option has the limitation that it is one-way only, you can’t revert the building procedure because the old objects will be removed. I recommend to always keep a backup of your scene before using this option. I should have mentioned that, sorry.

If you have no backup then try to apply the FM by pressing “Convert to Objects” in the FM panels, delete the constraints, and reset the scaling by selecting all elements and pressing Alt+S. After that you still need to create new groups for the elements but then you should be ready to go again.

Oh, and of course, you can disable the rescaling in the element group settings of the BCB (it was introduced to avoid initial collisions in the first place).

(dimitribastos) #1733

This was probably asked many times before, but can we expect a merge with the master for the fracture modifier build?


No problem, I’ve got plenty of back ups!

“you can disable the rescaling in the element group settings of the BCB”

:+1::+1::+1: Will give this a shot.

Thank you!

(JTA) #1735

We are working in the 2.8 code base already but there is a lot still to do since physics will not be updated in 2.8 until the second wave of 2.8 development later in 2019. Also it will take me a while to update the documentation.

So like mcbeth’s investment in 2.79x Fracture Modifier is still a good way to go. FM 2.79x will be around for a couple more years at least since we have such a big user base.

I’ve given more details in earlier posts if you scroll back. We’ll keep you updated.

Until then Fracture ON with 2.79x!

(JTA) #1736

@dimitribastos - hhhmmmm…actually could you clarify your question a bit? When you say master I assumed you meant 2.8. Do you mean current master with the Cycles fixes but not the 2.8 stuff?

(dimitribastos) #1737

Sorry. What I mean is: if and/or when we will be able to download a blender version from blender.org and that version will come with Fracture Modifier. I think this is clearer. Thanks!

EDIT: just saw your previous post. Thanks for the feedback!

(JTA) #1738

Ah okies. So yes, it will be going into 2.8. We will know more about when during the physics update scheduled for later 2019.

FM uses some really deep hacks to work around blender’s coding choices. Also FM will have to pass review for 2.8 after the team works with the core devs on the 2.8 physics in the second wave of development.

So FM 2.8 downloadable in the official distribution is on both our team and the core blender dev team’s roadmaps. It may take a while and a bit of work since FM is such a powerful tool and heavily integrated with blender and Bullet Physics.

BTW, props to our team and of course Scorpion81 for a brilliant job coding something so powerful. With that power comes responsibility to provide a usable tool. Thanks also to all the users posting on this thread with feedback and showing their work.

Fracture ON!
(…kind of like Flame ON! but a little bit different, lol. Explained for the nubes here : )

(dimitribastos) #1739

I would like to use it already, but I’m a 2.8 addicted. :slight_smile:

(wolfie138) #1740

ok, just as a warning to others - sometimes if you accidentally open a Fracture file in normal Blender it will be apparent by just closing immediately; other time (as i’ve just found out) it will open fine and you won’t notice - and if you save, it seems to destroy the fracture. i should have noticed the splash screen, that’s what i get for opening several different files to cross-ref and append etc.
so, attempting to rebuild something, in the FM build i’ve opened my file, deleted the wall, the helper and the trigger, and appended their Objects from a secondary file. When i do, the trigger and wall are pink, not green, despite having the Fracture and rigid body. if i tweak the wall - i removed a material - it turns green again. regardless, although my keyframed stuff still runs, the wall is no longer affected by the trigger.
if i untick Animated, the wall crumbles w/out waiting for the Trigger. If i untick Triggered, the wall doesn’t react. do i need to append something other than just the Objects?

EDIT - typically, the very next thing i try fixes it! The answer was the Trigger - although it had a rigid body, like the wall it was showing pink and seemingly not a rigid body. removing the RB and reapplying fixed it.