clipka <ano### [at] anonymousorg> wrote:
> Am 26.01.2013 15:43, schrieb Trevor G Quayle:
> > clipka <ano### [at] anonymousorg> wrote:
>
> >> (0) [optional, just for speed] If the cubes' bounding boxes don't
> >> intersect, the cubes don't intersect.
> >>
> >> (1) If any corner of the smaller cube is inside the larger cube, they
> >> intersect. (No need to test the other way round.)
> >>
> >> (2) If any edge of the smaller cube intersects any surface of the larger
> >> cube, they intersect. (Again no need to test the other way round.)
> >>
> >> (3) In any other case, they don't intersect.
> >>
> >>
> >> Note that this only works for cubes, not for generic boxes.
> >
> > #2 is the key.  if #1 is true then #2 is true as well.
>
> Not necessarily: The smaller cube could be entirely contained in the
> larger one.

OK, you are right about that, didn't think of that.  The way to check that is to
check for intersecting spheres based on the inner boundary (distance from cube
center to face).

So:
1) check outer boundary spheres (radius = cube center to cube vertex), if they
don't intersect, cubes don't intersect.
2) check inner boundary spheres (radius = cube center to face), if they
intersect, cubes intersect or are nested.
3) for remaining cases, check edge line/face plane intersection points.


-tgq

Post a reply to this message