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I'm trying to fracture an object after it hits the ground. Basically, it's falling and hits the ground, then another object smashes it. I don't see any way to keyframe the execution of a fracture from the fracture modifier, so I'm wondering if I could simply turn the entire modifier on or off with keyframes.

Thanks

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  • $\begingroup$ No, I dont think there is as far as I know, but most modifiers have an Influence or Value property that can be keyframed, and when put to zero can effectively "disable" a modifier. Not sure it is available for the fracture modifier though. $\endgroup$ – Duarte Farrajota Ramos Mar 21 '17 at 2:44
  • $\begingroup$ If I get you right, you don't need to disable fracture at all. I haven't downloaded an updated build for a while, but it is doable. You just want an object to fall to the ground, and stay intact until another object hits it, correct? $\endgroup$ – Timaroberts Mar 21 '17 at 2:57
  • $\begingroup$ @DuarteFarrajotaRamos, that's a good point. Although so far I haven't found anything like that yet with the fracture modifier, but I will keep looking. $\endgroup$ – lakerice Mar 21 '17 at 3:04
  • $\begingroup$ @Timaroberts yes, that is exactly what I want to happen. I just need to find some way to keep the object intact until it gets smashed after it hits the ground. $\endgroup$ – lakerice Mar 21 '17 at 3:05
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To achieve this effect you can use the Dynamic Fracture Mode for the object to be fractured. Note that the Dynamic threshold will cause the object to fracture on impact after falling if set too low. Make adjustments between this and the mass of other objects that interact with the simulation so that things work as desired.

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The object that will fall onto this object needs to have a sufficient amount of mass in order for the fracture to work. Here, the sphere has a mass of 25, the rest of the rigid body settings are at defaults.

You may need to increase steps per second in the scene properties if the simulation seems to be unstable, just be sure that all transforms (rotation, scale) are applied.

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  • $\begingroup$ alternatively you could still use prefracture and constraints with higher constraint search limit (per mesh island) and higher search radius (this depends on the object size). The more constraints you have plus maybe higher solver iterations lets the object look more stable. You can then control the breaking via angle for example. Additionally you could use autohide to let inner faces disappear as long as some distance threshold between is not exceeded. All this just in case Dynamic Fracture still makes problems :) It is not really intact until it hits something, but it looks intact. $\endgroup$ – scorpion81 Mar 21 '17 at 8:52
  • $\begingroup$ This definitely worked thanks for the solution! $\endgroup$ – lakerice Mar 21 '17 at 22:59
  • $\begingroup$ @scorpion81, it has worked with dynamic fracture, but out of curiosity, are you describing the effect of shards only appearing where the object has been impacted? Not sure if I fully understand your suggestions. $\endgroup$ – lakerice Mar 21 '17 at 23:01
  • $\begingroup$ no, the object would already be fractured into shards. The constraints just hold them together in theory until impact, but you then have carefully to adjust the settings to get the desired effect. Glad it worked with dynamic fracture though :) As a side note, with prefracture you could have used Extra Particles with one or more helper objects with particle systems, in order to determine where you want smaller shards, e.g. near "planned" impact points. This way shards farther away would be bigger, but still there. My suggestions were only thought as fallback in case dynamic wouldnt have worked. $\endgroup$ – scorpion81 Mar 22 '17 at 9:30

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