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Basically, I have an object (A) that is falling, hits the ground and then gets hit by another object (B). When the A lands, it stays in tact. Then B hits it and fractures using dynamic fracturing in the fracture modifier. However, it fractures the object A entirely...but I only want the surface to fracture. Is this possible? Keep in mind no meshes can be separated in object A beforehand because it will fall apart in mid air before it hits the ground.

Here are some examples of the type of fracturing I want:

enter image description here

enter image description here

Thanks!

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I guess you are still asking about how to fracture your cartridge/crowbar scene ? I tried now with prefracture and one particle helper object and the fracture addon "timing" feature, where you basically can delay the FM simulation by x frames. This just simulates the intact object and records keyframes, then it plays it back as animated rigidbody. After Frame X is reached, the animated checkbox will be disabled by keyframe and simulation takes over. The helper object was carefully placed near the supposed impact point of the crowbar, and additionally some weak constraints were created to hold the shards farther away from impact together. In this blend's case X was Frame 85.

Edit: in this case i even could disable the constraints entirely. Looked even a bit better :)

Looks like this:

cartridge-crowbar

But take a look into the blend I prepared here.

Edit: Reworked version of the new question blend:

I did the following:

  1. Removed all modifiers from the cartridge
  2. Removed solidify from ground, extruded it properly
  3. Set origin to geometry on ground
  4. Made the ground a Box shape, with 0.0 margin
  5. Moved the helper into the cartridge, so its particles "intersect" it
  6. Since the crowbar impacts 2 times, I duplicated the helper and moved it
  7. added FM with Voronoi+Bisect and Extra Particles and Helper group
  8. disabled Uniform in FM, executed fracture again
  9. constraint settings: "vertex" (set the radius to a low value before switching to vertex !!!)
  10. breaking angle to 5 degrees

Then I played a bit around with different angles, constraint settings (centroid vs. vertex, limits, search radius, breaking angles) but it turned out those were the best settings imho. You get 2 impacts with them without the cartridge sliding away too quickly. But it breaks a bit more than just making a hole into the surface. Note: the animated crowbar acts as if it had infinite mass (i assume) so changing its mass while being animated should have no effect in theory.

Edit: final attempt of mine, couldnt get much closer... although tweaking for a while. Converted the keyframe animation into deltas and rotated the cartridge... so it gets a better hit pattern according to the crowbar anim. Not sure if there are still too many shards, note some variation in shard size adds up some detail (imho). If still too many, feel free to reduce particle amount in helpers or alternatively the shard count in FM (applies to uniform) Tried hard so the top is smashed and the bottom stays relatively intact.

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  • $\begingroup$ Yes same scene...although I made a lot of changes since that .blend was uploaded, including recreating the cartridge from scratch with the solidify modifier. Hm I really tried to replicate your results, but it doesn't seem to be working. It seems as though every single face flies off like lego pieces being taken apart instead of a nice realistic fracture like yours. I've uploaded my recent .blend to this question. $\endgroup$
    – lakerice
    Commented Mar 23, 2017 at 2:51
  • $\begingroup$ Hmm, the timing functionality seems to have an issue... it decomposes the object to its original islands somehow, you might need to refracture it after the keyframes have been created. Let me try to post the blend in my answer or I make a new answer. $\endgroup$
    – scorpion81
    Commented Mar 23, 2017 at 10:08
  • $\begingroup$ This is much better thanks! However, I'm still trying to make it so that it fractures in a more plastic way rather than something like glass. In other words, a few shards and starting at the top first, then the bottom. I'll post an example in my question. Sorry for all the trouble! $\endgroup$
    – lakerice
    Commented Mar 23, 2017 at 17:03
  • $\begingroup$ Sorry for the late response...was working on it for days and tried a ton of things. I think I got a healthy compromise with the shard count though. Otherwise, without the helpers it just causes the lego effect rather than the rough fracture. Thanks again for all your help @scorpion81; I wouldn't have been able to get this far without it. $\endgroup$
    – lakerice
    Commented Mar 27, 2017 at 3:01

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