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For certain effects like glass shattering and falling objects cracking to reveal their inner contents, are there any tricks or ways to implement these fracture physics without having to use actual physics simulation? Also, what are the trade-offs if I don't use real physics simulations?

Since the effects don't really require exact simulation, an actual physics simulation may be too expensive and wasteful.

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up vote 5 down vote accepted

I assume by "real" physics you really mean "realistic" physics. In almost every game that includes physics, unless it is a key feature of the game, the developers will take shortcuts to reduce processing time.

Quick answer: fake it with an animation.

Little longer answer: Reduce the number of pieces you process. You'd be surprised by how much time you save by processing half the number of pieces. Also having the objects pre-broken, meaning the interaction with the user doesn't determine where in the object the fracture is, will reduce processing time.

Trade offs for faking:

  1. Doesn't look real
  2. Not very dynamic
  3. I'm sure there's others

Trade offs for reducing number of pieces:

  1. If you are using realistic physics the player may not even notice.
  2. Still can be dynamic.
  3. Simulated physics.
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In X Men 2, Magneto shatters his glass prison with several marble sized metal balls, youtube.

In the DVD commentary the designers explian how they did the breaking effect. It was too computationally intensive to fully simulate it, instead they had an artist determine where the breaks would be (and where they'd look good). Then they scripted when the pieces would detach, the falling glass shards were physically simulated.

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