Might have to model the wall as two pieces. Model both the wall with appropriate kind of hole cut into it, and the piece of the wall that gets blown out. Fit the two togethter seamlessly, and then do the fracture just on the stuff getting blown away.

May also want to use particle emitter to make some extra debris, and hide your various bits and chunks to be emitted off the visible part of the scene. That should give more variety than the shard shapes the voronoi fracture makes.

There might be a better solution, but that's the one I could think of off the top of my head.

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Barbequed Pixels?

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