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When creating rigid body simulations where objects will come into contact with other objects and as a result change position, you'll find situations where maybe a little extra binding agent needs to be added in the mix in order to make those breaking-apart sequences more realistic. If that occurs, a special Reactor helper object called a fracture can assist in holding things together. Let's see how adding a fracture or to our shards of glass changes the way that things break apart. We'll do that using the Breaking Glass05 file, which we brought with us from the last video.
We are going to want our fracture helper to include all of our glass objects, so let's first make that selection. We can easily do that using the select by name list by typing H. From the dialog starting at the top, we'll select all the objects named Glass Shards. Let's now head to the Reactor toolbar on the left-hand side of our screen. The Fracture Helper, an icon named fracture, can be found about three quarters the way down the list. It's the button that looks like a cube with a zigzag line running through it.
Once you find that command, go ahead and click. With the fracture now having been added to our broken shard objects, let's head to the Modify column. The fracture provides an additional set of controls as to how objects in the fracture break apart. The Energy Loss value is probably the most influential fracture setting. What it controls is the amount of extra kinetic energy that is lost during a collision due to the breaking apart of the fracture bonds. Put another way, energy loss kind of dampens a collision with higher Energy Loss values causing things to hold together that much longer.
So, brittle objects would have a lower Energy Loss, while something like maybe rupturing concrete would appear more realistic in the way it breaks apart by using a higher Energy Loss value. Let's see what changes the fracture might have made to the way our glass breaks apart. To run a preview, let's this time use our Quad menu. That's Shift+Alt+Right-click. Then we can simply press P for Playback. With the addition of the Fracture Helper being now included in the calculation, you'll notice the way that things have slowed down dramatically within that Preview window.
To temporarily change that, we'll adjust our Substeps value. In the Performance pulldown menu, in that little column, we'll take our Substeps to 4. Let's now play through again. You can see how the glass shards appear to be holding on to each other just a little bit longer. Let's experiment with a different Energy Loss value and we'll see how that looks. Back on the right-hand side, let's change the Energy Loss to let's say 0.1. Once you've done that, let's Preview again.
With the lower setting, you can see that the additional glue laid on by the fracture doesn't have quite as much impact this go-round. Let's see what an Energy Loss value of 0.5 would look like. You can see that with each change in the Energy Loss value we're getting a little bit of a different result.
How does that compare to not using the Fracture Helper? Let's do this. After closing the Preview window on back on the right-hand side, we've got a check mark we can activate called Disable. Let's do that. You'll find that control way down at the bottom. I've got to be honest: because of the extremely lightweight of our glass pane, we really don't need that extra level of fracture binding.
So in this case, why don't we simply leave the fracture being disabled? Now, if you wanted, as an alternative you can always go in the scene, select it, and delete it from the sim. Either way, removed or disabled, it will have no impact on our results. So that will give you a little background on using Fracture Helpers with a Rigid Body Simulation. If things seem to be exploding apart too quick or with what seems to be not enough resistance, make sure that you consider using a fracture to help alleviate that problem. Let's go ahead and save our scene up as Breaking Glass06, and we'll take it with us into our next video where we'll start adding a few materials to our scene.
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