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We have three different ways of breaking in the Sandbox.

1. procedural breaking
2. jointed objects
3. pre broken objects


1. Procedural breaking

In this technique we are using direct physicalized render geometry. There are no extra proxys which would make this method very heavy on physic performance. It’s used for glass and trees. We define a subtract object which will be subtracted from the object placed in level. This object is also giving the mapping and material details for what the cut is.


2. Jointed objects

A Jointed Object contains different sub objects which are held together by joints. Joints are helper objects which give strength information for the connection at this point of the object. After breaking a joint you could also define pieces which will displace the old object. You can also joint procedural breaking objects.


3. Pre broken objects

Pre broken objects consist of main part, remain part and pieces. The main part has health. If health is over, the pieces and the remaining part is spawned. This is a more or less historical object class. We try to avoid this kind of breaking object and rebuild it with jointed versions instead.


Vegetation can only include procedural breaking. But there are also two more techniques which allow branches and leaves to bend.

1. touch bending
2. wind bending

1. Touch bending

This is used for vegetation and object collision. It’s a bone which is instanced on all meshes in one object which share the same mapping coordinates. You can use different amount of bones for one object and give them different amount of pivots. When ever something hits one of these bones, the object part will bend.

2. Wind bending

Wind bending is vertex color based. We define different colors for different behaviors. Blue is for up and down, red for side movement and green for overall variation. Later in shader you can say how strong which color should bend. This way you can tell a palm leaf to bend more on the outer side than on the inside.

Not every branch can break. This will happen in 5 years time when hardware has more power. Generally speaking, everything is breakable that we define to be breakable
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