Cylinder Convex Hull Tester

Hi,

I’m reading the CylinderConvexHullTester and I’m quite lost in terms of trying to understand the code. Could you give an explanation of how the Test function works? I would really appreciate it. Thanks in advance!

[RossNordby]

That’s a part of the hull face vs cylinder cap test. Each edge of the convex hull face (projected onto the cylinder’s cap) is tested against the cylinder cap’s bounding circle. Each hull face edge can contribute up to 2 contacts but may sometimes generate only 0 or 1.

Any contacts associated with a face edge are created at the endpoints of a line segment bounded by the original face edge and the circle. That span is represented by an interval from tMin to tMax.

If tMin is 0, that means the previous edge must have extended all the way to the vertex. Since the previous tMax case already created a contact, there’s no value in adding another contact at the current edge’s tMin = 0; the two contacts would be in exactly the same spot. That’s why there’s a tMin > 0 condition.

So the tester would only enter that part when the earliest intersection between the edge segment and the circle is somewhere in the middle of the edge.

[RossNordby]

It’s more intuitive if you flip it around- clip the line segment against the convex face.