What exactly does “Contains” mean in XNA?

Question

A pretty specific question if anyone knows the answer: What exactly does "contains" mean, in the context of BoundingSphere1.Contains(BoundingSphere2)?

If i have a smaller sphere inside a larger sphere, does the smaller sphere "contain" the larger sphere as in the entirety of its volume is also the volume of the larger sphere? Would that return a ContainmentType.Contains?

Thanks!

Answer 1

From the MSDN page for the BoundingSphere.Contains method that takes a BoundingSphere parameter:

Checks whether the current BoundingSphere contains the specified BoundingSphere.

It returns a ContainmentType enumeration which

Indicates the extent to which bounding volumes intersect or contain one another.

Specifically:

Contains: Indicates that one bounding volume completely contains the other.

Disjoint: Indicates there is no overlap between the bounding volumes.

Intersects: Indicates that the bounding volumes partially overlap.

If BoundingSphere1 is smaller than BoundingSphere2 then I suppose BoundingSphere1.Contains(BoundingSphere2) would return a ContainmentType.Intersects result instead of a ContainmentType.Contains result since it doesn't "completely" contain the other. On the other hand, BoundingSphere2.Contains(BoundingSphere1) should return ContainmentType.Contains since it "completely contains the other."

EDIT: I've updated my answer after reviewing the documentation again. Initially something sounded vague but now I think the emphasis in the enumeration details of "completely" and "partially" for Contains and Intersects, respectively, strengthen my expectations. I can't test this but this sounds reasonable.

Answer 2

As far as I can tell this is how I am interpreting your assumptions.

BoundingSphere1 is a big circle. BoundingSphere2 is a small circle.

Lets say BoundingSphere2 is entirely contained within BoundingSphere1. From what I understand, you think BoundingSphere2 "contains" BoundingSphere1.

In actuality, BoundingSphere1 "contains" BoundingSphere2 because all of BoundingSphere2 is within BoundingSphere1.

You are basically trying to found out if a Sphere is within another Sphere.

so BoundingSphere1.contains(BoundingSphere2) will be true, but BoundingSphere2.contains(BoundingSphere1) would be false.