# Destruction of Meshes

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Hi guys. I was wondering if anyone had any thoughts on breaking geometry? I've been looking around and I can't seem to find much on the subject. Lets take a simple example, a glass bottle that isn't hollow (to begin with - a normal closed mesh)

I thought that maybe a recursive split with arbitrary planes. So you draw a plane that divides the mesh into two, then do the same to these two bits etc, but then one would need to cap these bits that are made.

Maybe representing the whole mesh as a voxel set and then using something like bullet physics on each block? That might look a bit poor later on though (though perhaps voxels may have something?)

Essentially the explosion or breakage doesnt need to be utterly correct but a good looking set broken bits with some specification of where the break starts would be the goal.

I believe Red Faction and similar tend to precompute their destruction animations to a degree. I cant seem to find the original post I saw on this. I'd have thought this would be a common problem with a few solutions (even though its a tricky one. Anyone know of any papers or similar on the subject?
Cheers!

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Mussi    4409
Most games use multiple meshes to achieve this, one that's whole and others that are broken up inside a 3D modelling tool. All major 3D modelling tools have a so called boolean operation that allows you cut trough/add/subtract a mesh with another mesh, which allows you to easily break up a model.

Once you have these separate meshes, there are two ways to go about destroying them. The first option is to animate the destruction inside the 3d modelling tool and simply replace the whole mesh with the animated destroyed mesh once it gets destroyed. The second option is to use a physics engine to handle all the parts after destruction. So after for example the bottle gets destroyed, the mesh containing to whole bottle is replaced with multiple meshes of broken pieces that form the bottle. These pieces then get controlled by the physics engine. The first option is easier to implement and faster computation wise, but it's less realistic.

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wildbunny    550
[quote name='OniDaito' timestamp='1305845331' post='4813225']
Hi guys. I was wondering if anyone had any thoughts on breaking geometry? I've been looking around and I can't seem to find much on the subject. Lets take a simple example, a glass bottle that isn't hollow (to begin with - a normal closed mesh)
[/quote]

As Mussi says, most games use multiple meshes (Killzone 2 for instance) to good effect. If you want the cutting edge (so to speak), google 'Fracture' - its got an entire army of researchers dedicated to it

Cheers, Paul.

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Thanks guys! It seems that this is the accepted way of doing things ( the only way really) from what I've found out. Cheers for the headsup!