Slime wrote:
> Is this what POV-Ray actually uses for the intersection of a ray and a 
> sphere? I just spent half an hour working out both the geometrical 
> interpretation of this and its equivalence to the result of the quadratic 
> equation with the coefficients that Andrew posted, and I'm really impressed 
> at how simple it is. And annoyed at the fact that I never could have come up 
> with it myself =)

Yeah, Pov uses the exact same method. It is very simple and fast method.
Pov also has one additional check, which I'm not sure is worth it. POV
also returns both hits always. I only return the hit in front of the
ray. I have no use for the other.

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