Thinking about hybrid raytracing, hence the following question:
Suppose I have two solid spheres $s_1$ and $s_2$. We know their centres and radii, and we know that they have some overlapping volume in space.
We have a typical 3D graphics setup: assume eye is at the origin, and we are projecting the spheres onto a view plane at $z = f$ for some positive $f$. The spheres are beyond the view plane and don't intersect it.
Let $c$ be the circle in space that is points on the surface of both spheres, i.e. the visible (from some angles) 'join' of their overlapping volumes.
I want to calculate if any of $c$ is visible when projected onto our view plane. It might not be, if $s_1$ or $s_2$ get completely in the way.
Any ideas for approaching this?