What the meaning of Bounding Leaf, and when we should use it

Question

hi, i have read book about java 3d programming that provide by sun .
In chapter 3 i read about Bounding Leaf but i can't get the point, would someone explain it to me in simple way and easy to understood?
thanks

Answer 1

Basically, when you use, say, a BoundingSphere, you're setting the bounding region to be symmetric about the point (0, 0, 0) of the local coordinate system of the object it is bounding/activiating/scheduling.
A BoundingLeafNode specifies an alternate coordinate system about which to bound the behavior, allowing to to be non-symmetric, and allowing items in different positions to share the same bounding region.
The API Specification Guide provides a good example of where this could be useful.
Let's say you were designing a room with three point lights, in different spots about the room. You want the reqion inside the room to be the bounding region. But each light will see that region differently, because their local coordinate systems are different. A boundingLeafNode would define the room from a single local coordinate system, and all the lights would see that region the same.
Ok, you say, but you could still have used a BoundingBox object. Correct. But now imagine that there are 30 lights. I certainly don't want to design 30 Bounding Boxes so that each one specifies the room in it's own coordinate system. And imagine if these lights were moving. Lets say you want to simulate a disco-ball. Now, the bounding region would have to change each time the lights move. But not if the bounding region is specified by a static coordinate system.
That should give you a pretty good idea of what the advantages are.
- Adam