How to efficiently add complex bounding boxes to your objectsΒΆ

It is often important to simplify the bounding box of complex objects (ie, replace a complex Triangle Mesh by a set of simpler boxes or spheres for instance) to maintain the performances of the MORSE physics engine (Bullet).

Here is the “how-to”.

Let’s consider your object is named for instance RollingChair.

../../_images/object_grouping1.png
  1. Append a _mesh prefix to its name (for instance RollingChair_mesh).
  2. In the Physics properties panel, disable the collisions for this object (No Collision).
  3. Create plain boxes and put them around your object to shape the bounds. Name them after your object, appending a prefix (like RollingChair_bb_xx, cf image above).
  4. Apply scaling (Ctrl-a) on each boxes.
  5. Create a new Empty and name it after your object (in our example RollingChair).
  6. Parent all bounding boxes + the original object mesh to this empty.
  7. In the Physics properties, set the empty to be a RigidBody, set the collision bounds to be Convex Hull and check the Coumpound option (hence all sub-objects are used to create the global collision box).
  8. Set the collision properties for all other boxes belonging to the bounding box, not forgetting to set the radius to be smaller than the box. All the boxes must have their Collision bounds set to Box and Compound must be selected.
  9. All the bounding boxes can be set as well to Invisible in the same Physics panel.

Check the passive objects doc for details on creation of objects in general.

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