[ODE] Laser range finder

[Adam D. Moss]

John Miles wrote:
> FYI, be careful using really-long rays with the dTerrainY/Z contributions.
> If you fire a ray at an angle that the terrain collider doesn't trivially
> reject (e.g., 45 degrees from just above the center of a world to a point
> beneath one of its corners) , performance suffers greatly compared to an
> orthogonal ray, or a shorter one.
> 
> Or, that may be a general property of the quadtree space, for all I know.  I
> didn't investigate.

Rays have AABBs like anything else, and unfortunately of course for a long
ray which isn't mostly-major-axis-aligned, the volume of that bounding box
will be so huge as to be almost useless, meaning a real ray collision
test against everything within that volume regardless of the type of space
used.

A ray can be split into smaller rays at the app level to offset this,
it's just a mild PITA to be doing manually.

Regards,
--Adam