The Bound of Rigid Body (New for 5)

The Bound of a physics object is a range that causes collision with other physics objects. The shape of the bound can be default or customized. The more complex the mesh is, the more system loading you will encounter. Therefore, using the bound as simple as possible may produce physics reactions while minimizing the use of your PC system resources.

Bound and Collision

After you assign a bound type to a rigid body, the range for collision will be defined. The collision does not necessarily happen according to the shape of the rigid body, but to the shape of the bound instead. The basic bound types are Box, Sphere, Cylinder and Capsule; and the complicated types are Convex Hull, Bounding Mesh and Self Mesh.

A diamond is assigned with a Box bound.

The physics balls collide against the bound instead of the skin of the diamond.

Convex Hull and Self Mesh

Convex Hull

Self Mesh

Bounding Mesh

The Bounding Mesh is a representative model, mostly a box, surrounding an object. By displaying the bounding mesh instead of the true mesh of the object, you may ease the system loading and increase the processing speed of iClone. In iClone, the prop templates in the 3D block category all contain a bounding mesh in a box shape. Therefore, if you choose to use this bound type for the 3D blocks, then their collision area will all be like boxes.

Viewing Bounding Mesh

If you wish to check the bounding mesh of an object, then you may follow the steps below:

  1. Select the cone.
  2. Right click on it. Select the Display item in the right-click menu.
  3. Pick the Bounding Mesh command to show the object in bounding mesh mode.

If you choose to use the Bounding Mesh as the collision area for the rigid bodies, then you will actually be using the boxes surrounding them.

The bounding meshes of the three objects.

Use the Bounding Mesh as the bound type.

Creating Custom Bounding Mesh

By default, all object's bounding meshes are mostly boxes; you may create custom bounding meshes by using external 3D modeling tools.

Since real-time physics collision detection depends on the simplicity of a collision bound, for high-polygon-mesh objects, it is highly suggested that you create custom collision bounds to approximate the shape and keep speed and correctness.

  1. Launch your favorite 3D modeling tools (Maya, 3DS Max or any one that can export models in FBX format)
  2. Create a model, name it. (Helix for example)
  3. Create another model.
  4. Name this new model as Helix_Boundingmesh (case sensitive).
  5. Export them together in FBX format.
  6. Load this FBX into 3DXchange 4. Convert it to .iProp for use in iClone.
  7. Import the converted prop and display its bounding mesh. You will then see that the bounding mesh is a differnt one than the one you created in the 3D modeling tool.

    Bounding meshes with a high mesh number.

    Bounding meshes with a low mesh number.