Destructable Mesh blowning apart too hard

Development World Creation
1

I have destructible meshes that I have working I think about as good as I can get on the destruction part.

But I have a few pieces I want to resolve.

A.) when my mesh finally decides to fracture it blows apart with a ton of force. Which knocks into other meshes and such. For example I have two DM stacked if the bottom one fractures it sends the top one flying about 100 meters in the air upwards. I want to damping that so that it just falls to say.

B.) instead of having parts blowing apart outwards, I want more of just a crumbling affect to happen, can’t quite pin point the best settings for that yet.

C.) Can’t get smaller chunks to break apart. Or if possible just disappear together after X seconds.

D.) Crumbled parts seem to have a weird lighting aspect where they start to “flicker” while laying on the ground. Not sure if it’s just something where I need to fully build lighting on high, or implement dynamic lighting for the whole scene?

2

I managed to solve for C.) well I can use the onComponentFractured set a delay and then self destroy actor. Still can’t get it to crumble the debris. For A and B I can set the linear and angle damping but they then just cause my debris to fall in slow motion. Want them to not apply force to others, but still fall fast downwards.

3

I may be guessing here, but further into the damage section, you can ammend " Chunck Speed", “Debrie Lifetime”. (If you have not already played with these).

No luck here with the lighting.

4

Hi Keeperofstars,

What version of the engine are you using? If you’re using 4.5.1 or earlier I would recommend using the 4.6 preview until 4.6 is fully released here soon. There have been some great changes with Destructible Meshes like getting the chunk parameters to function properly now.

I have a sample project I made for another user to test and posted that in the community tutorials section at this link: https://forums.unrealengine.com/showthread.php?52865-Sample-Project-to-destroy-Destructible-Mesh-with-Line-Trace-and-Ball-projectile

In this sample project I made two types of projectiles. A line trace that will apply a radial damage at the hit location of the trace and the other is the yellow ball projectile from the FPS Template.

You will need at minimum the 4.6 preview (which you can download from the launcher) to open the project.

With that said let’s dive into some of your issues you’re having. :slight_smile:

When you reply back can you suggest/show a shape of the you’re trying to create the fractures for, along with the fracture Cell Site Count? With this I can then start trying some rough settings to better suggest more specific results.

From your description with this problem it seems to me that you’re using the FPS template projectile with the yellow ball, correct? For something like this I would probably suggest adjusting the mass for the DM itself but there is a known issue with mass not functioning properly for DMs (UE-5642).

Needless to say there are probably some settings here that can be adjusted to give you better results. Let me know if you’re using the ball projectile (which will give you the least accurate results) or the line trace projectile and I can suggest some things that may or may not work in your case.

Provide the information I’ve requested above and I can suggest some things that may work in your case.

There are a couple of things with this. For the first part where you want smaller chunks to break apart. This is not possible with the fracture tool in the engine. There is only one layer of depth that is provided stock. If you want to have multiple fracture levels (ie. shoot a pile on a wall, a large chunk falls and fractures into smaller pieces when shot or hitting the ground) you’ll need to use PhysX Labs. There is the standalone application for PhysX Labs or you can get the 3Ds /Maya plugin. The can be grabbed from Developer.Nvidia.com for free once you signup with an account. Well worth it in my opinion as you can get much more control over your mesh and choose how you want your mesh to fracture based on image masks rather than just a Voronoi method.

Here are some of their tutorials to give you a better idea:https://developer.nvidia.com/apex-destruction-physxlab-tutorials
Specifically take a look at the second video for cutout fracturing to see what I mean.

For the second part, there are a couple of ways to handle debris timeout. Again, depending on how the mesh is setup you can have the chunks disappear after a set or fade out between two specified times. The second option requires a few more settings tweaks but is possible.

Here is a settings setup to get the chunks to fade over :

DM_FadeChunks.PNG
DM_FadeChunks.PNG480×525 26.1 KB

I used these settings for my line trace weapon. I have not tested them with the projectile ball. Results may vary for the destruction.

I’ll look into this one and see if I can offer any feedback.

Thanks!

Tim

5

http://screencast.com/t/8M7L3zbx
is the general setup of the models, each a wall segment with about 40 pieces so you get decent breaking down without too many huge chunks.
I’ve downloaded 4.6 and your project, going to take a look at them this afternoon. Currently though I am using the yellow ball from the FPS example. I’ve added a radial force to the projectile, and am applying it with Hit Event.
http://screencast.com/t/QI1mQXBqeUHY

I currently just using the built in tools so only have 1 depth to work with, if I turn on debris in 4.6 no matter what level i set it obviously just instant vanishes. Doesn’t follow the min for debris, but i think that is where I only have the one option for the depth layers.

in regards to the flickering, i’ve watched it more closely and it’s happening when the objects are on the ground, still but possibly having force or physics applied. After about 15 to 20 seconds on average they eventually slow in flicker and eventually stop flickering. So could be an aspect where the light doesn’t know how to reflect off the moving / falling objects, and even though they aren’t moving anymore the cpu hasn’t finished applying physics force, so the gpu thinks the items are still in motion maybe?

I’m going to play around with the two examples you have and look at some settings see if I can narrow it down to what I want, will also look at the lab tools to see if I can refine the results a bit.

6

So I played around with the examples, the ray trace is nice, but doesn’t apply the penetration force I sort of do want. I like how the yb projectile applies the force more so to the mesh as a bit of a whole. I just wish I could control how that force is applied. What i’m looking for is roughly taking lets say a cannon ball and shooting it at the wall so it crumbles and falls. There might be a bit of an upward explosion of the chunks but they should “weigh” so much that they can’t fly very high upwards, so the force of gravity on the blocks needs to be scalable I guess is the issue at hand. A way to apply mass / weight so the force knows it can’t fling the chunks sky high, cause the chunks weight offsets the force. Is there a way to deal with that aspect currently?

7

have managed to get a bit of the upwards popping to stop, at least to an acceptable manner at this point, still looks a bit off but for now it’s meh ok one of the bigger fish to fry aspects. Now the question is I got my wall chunks, I apply damage they crack and then break apart. Yeah but now I have a huge rubble pile I want to allow additional shots to remove / do stuff with such as break down further, or at least apply a sense of force to them. I can set the debris life but that can be a bit counter intuitive to the aspect of the player creates small crack but the wall unit still mainly held up still. aka the pieces haven’t really separated from each other yet. then poof the wall just vanishes leaving a huge open hole where the segment was. This can cause other aspects to fall down / around. I guess the challenges is with wanting the rubble to stay but make the player deal with it. The other aspect is if you try using a modular design aspect with DMs you run into the outwards force aspect and then disappearing rubble can cause upper areas to fall when they really shouldn’t.

Oh and anyway to have it so that if a DM falls without damage but hits the world surface / terrain that it will take damage?

8

If you need the fracture chunks to break apart further into smaller pieces you’ll want to use PhysX Labs (standalone app or 3Ds /Maya Plugin) to get more than one depth layer for destruction along with the ability to use custom masks for specific looks for your DMs.

Try setting the debris life to be a little longer. Also, you can try using the “Fracture Impulse Scale.” You may need a high value to start with and then work your way down to a lower value to fine tune. (By high value, I would suggest starting at a few thousand or so, if you don’t see results try higher until you see results)

Do you have yours DMs set to simulate physics and to Start Awake? Try unchecking Start Awake to fix this. This may work. Hard to say without knowing your specific settings.

If you want the player to deal with the rubble, then using the debris timeout settings above would probably not be a good thing unless you set them to a higher value that is after the player would have effectively dealt with them. In my experience using Debris timeout is better for objects that the player won’t need to mess with.

It’s a good thing to remember that even though you fracture something and it’s now a DM that the game doesn’t assume these things. If something is not behaving properly that means that it’s been told somewhere via a value or checkbox that it needs to use this behavior. Narrowing down what settings work and what don’t is part of tweaking to get the final results needed.

9

thanks for replies, i’ve been playing around with the PhysX labs to help provide better breaking apart details. Still having problem with a sense of pressure / weight on during the fracture, making things stacked on top sort of pop up in air. I’ve managed to work past it some, but having ability to set a DM’s weight and then having force + gravity affect the blow apart aspect could be a helpful way to really help control meshes. Right now it’s a bit tricky to get a radial force for lets say a cannon or rocket, to blow a mesh apart but have the mesh follow physics. It just blows apart in full force. Being able to dampin force along an Axis would really help I think. That way I could say dampin any force along +Z way down but keep my x and y force constant. Or apply some weight to gravity aspect.

One possible suggest would be a really detailed tutorial series that covers what a majority of the DM settings are and what they impact. It seems there are 5 new forum posts a day with people trying to better understand the settings etc.
I know we have the few community ones along how to make them, how to destroy them, but besides reading the stereo instruction wiki page on what each setting does, it’s a pain to piece together things. A few good movies showing what various combinations of different settings do, and mean could really help the community as a whole

10

Hi,

As I had mentioned before the mass doesn’t appear to be working fully in UE4 for DMs. I’ve entered the bug UE-5642. Without being able to set this you will probably not see the results you want. You may be able to use a radial force and place several around the top so that when it fractures it pushes away from that area to fake an effect. Just set the radial forces bottom half to be at the top. It’s not the best result but could probably help.

As far as tutorials go, it’s just a matter of looking at the documentation provided via the PhysX Labs Help Menu. A lot of the settings in there are carried over to UE4 and can be explained. We also have the doc that explains the properties here for reference in UE4: https://docs.unrealengine.com/latest/INT/Engine/Physics/Destructibles/DestructibleProperties/index.html.

The best way to learn the settings is to make a test map and start adjusting settings to see what affects what. This is where I started and I have a test level that is nothing but different setups and tests that I’ve experimented with during my with destruction meshes. Anytime I need to check something I open this map and test different settings. I would imagine it would be very hard to setup a series of videos going through trying to demonstrate every setting, but not impossible. Some of these need to be used in conjunction with other settings and really get specific results.

I will pass along the information for destructible video tutorials to our Docs team, but in the mean I believe the Nvidia documentation( developer.nividia.com via PhysXLabs), tutorials (https://developer.nvidia.com/apex-destruction-physxlab-tutorials), and the in-editor tutorials that can be accessed via the tutorials button next to the minimize button will be the best source of information aside from testing different setups manually.

Tim

11

yeah, the reference is good don’t get me wrong, but there are a lot of settings and clicking one can drastically change how the whole DM works. Having some better guideance on the aspects of how those settings inter work with each other is where the tutorials could focus some effort into. I read the reference and was like hmm ok i think that might do what I want or maybe not, can’t tell. Like I said just a suggestion, i know each persons affect will be different, but a good going over about what each means in um plain English wouldn’t hurt.

Anyways I have one more suggestion as a feature add on maybe. Know it’s not exactly the right place, but also figured I would ask to see if there was a way to currently control it that I over looked. The particle effect on fracture, is there anyway to control it’s location? Right now it’s sort of just in the middle of the mesh. Now I know once I setup the multi depth I’ll have more control cause I can set the particle effect for the smaller bits and pieces, so that will help some, but have a few cases where the whole thing breaks apart well, but then the particle is stuck in the middle about 10 meters above where the rubble is. Just floating in air looking out of place. Be nice to have it more tied to the fracture lines or chunks than the center of the mesh. Or possibly give it a x,y,z option at least. Also is there a way to control the particle emitter based on the mesh crumbling or such? Besides relying on the break down into multiple depths. So for example play for 5 seconds after chunk separation happens? So as a wall falls down for example and comes to a rest the particle effect stops. Besides just guessing on a random physics event?

12

I seem to be having similar issues. I made a large static mesh using the box brushes in engine and I have, after a lot of trial and error, got the desired behavior with the DM that was created in engine. It has a nice slow cracking before pieces drop out. However, I wanted to take advantage of the added capabilities of PhysX Lab so I exported my static mesh from UE4 as an OBJ and imported it into PhysX Lab and made some really great fractures. Unfortunately, when I imported the new DM into UE4, it basically just bursts like a balloon. After some adjustments, I was able to keep it from flying apart but the debris chunks are still launching out when hit. I can’t seem to get the same results that I get with the DM created in engine from the same static mesh.

13

I think some of our frustration is with the mass bug that prevents the DMs from having a sense of mass. So right now the engine see’s them as tooth picks getting hit by rockets. I found it much trickier to get the settings working right with the physx lab but I think the main problem is when you use the lab tools you suddenly get additional depth levels that now make about half the settings meaningful so what you learned with it being an ingame DM sort of goes out the window a bit and have to start working on the multi-depth aspects now, which act much differently. Kind of that whole trial and error aspect over again.

14

So as I keep working with DM’s just ran into another challenge or two. They are related to this thread still cause has to do with force.

I have my DM wall pieces. And have made a DM for use as a projectile. I shoot the projectile and it hits the wall piece and blows apart, works perfect, except it applies a ton of force when it blows apart. can knock over a ton of things as the shrapnel flies over the place. What settings if there is any currently to have a DM just fall apart without the pieces causing force to be applied to anything when they break apart. Basically it breaks apart but zero force is sent out as a result of the fracture? I want the mesh pieces to break apart etc have collision, but not cause any force to be applied. I know it’s probably something that will be resolved with the weight / mass bug fix. As the projectile will have far less mass than what it’s hitting, but till then any thoughts?

Other issue I ran into after the DM breaks apart it collides but has stopped simulating physics. Nothing to horrible and I can see why but means I have to add a few things in blueprints to change up how the projectile works when hitting a destoryed DM versus a “live” one.

15

A) I have had some luck controlling the force of explosion by adjusting linear and angular damping. Create a blueprint from your Destructible mesh, look in the Destructible component under physics. i set them both too one and got a nice crumble, at 100 i got a kinda frozen fracture effect.