Is there a way to render transparent objects that have been pre-fractured with the Cell Fracture addon?

I know you can kind of get this to work by parenting the original object to one of the shards (or simulating it by itself) and swapping the visibility of the objects when the shards fly apart: enter image description here

However, It is obvious that it suddenly breaks the entire object on impact and just doesn't really look right. (the animation is slowed down at that point so it is more visible)

Is there a better way to do this?

  • $\begingroup$ The object switch appears to be happening one frame to soon (pre-shattering). Having some small fast moving fragments would help sell it too. $\endgroup$ – Aldrik Jul 17 '13 at 22:16
  • $\begingroup$ Just wondering, how did you switch the sphere to the multiple shards with animation? $\endgroup$ – Daniel says Reinstate Monica Jul 17 '13 at 23:28
  • $\begingroup$ @DantheMan I animated the render visibility in the outliner (right click on the camera that toggles render visibility and pick insert keyframe), so the shards were all hidden and the sphere was visible until the frame before the shards broke apart, then I switched it so the shards were visible and the sphere was hidden. $\endgroup$ – gandalf3 Jul 17 '13 at 23:42
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    $\begingroup$ You'll probably also want to increase the bounces so that it doesn't look so dark initially $\endgroup$ – Greg Zaal Jul 18 '13 at 7:05
  • $\begingroup$ @GregZaal Yes, this was just a very quick render to illustrate the problem, though that probably would help. $\endgroup$ – gandalf3 Jul 18 '13 at 19:38

Although being very late to the party, i would suggest the Fracture Modifier Build as a possible alternative. There you have a possibility to auto-hide inner faces, auto-merge the cracks (well its distance based, so its a bit limited... means if the distance is lower than the threshold again, the face will be hidden again) and "fix" the normals of smooth, fractured meshes. Btw this is a prefractured mesh here.

Would look like this for a very quick render of a glass sphere.

glass autohide

Links to builds are here


or here (latest windows build): http://graphicall.org/1148


Take advantage of the node compositor and render layers. If you put the original (non-fractured) object on a separate render layer, you can smooth out the transition. Basically, the idea would be to reduce the opacity of the original object's render layer over the span of a few frames rather than use the hard swap that you currently have. Stretching that transition over more than a couple frames will make the change less apparent.

This can also be done from the VSE, but you'd need to either use separate scene strips or render the animation twice (once with the original object and once with the fractured object).


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