[Shootout-list] Ray tracer developments

[Sebastien Loisel]

> The inheritance hierarchy is certainly one of the most verbose parts. But=
 what
> would you use instead? You could use a tagged union, but that is much mor=
e
> common in C than in C++.

I've got a lot of work so I haven't looked in detail, but I suspect
you can replace everything by a single "node" struct, with a list of
children. If the list is empty, it's a sphere, otherwise it's a group.

Sebastien Loisel