User of over_point causes inside shading test to fail

Hello zass,

For that test ("Shading an intersection from the inside"), there should not be any shadow, because the light source and the ray are both on the inside of the innermost sphere. That is to say, the innermost sphere is centered at the origin and has a radius of 0.5, and the light source is located at (0, 0.25, 0) --- inside the sphere --- and the ray starts at the origin, also inside the sphere.

If you're getting shadows for that test, it might be because your over_point is on the wrong side of the sphere. Are you adjusting it by the _original_ normal, or by the normal after you flip it (based on the "inside" flag)? You need to make sure you adjust over_point by the adjusted normal, otherwise it'll be moved outside the sphere, which is wrong for this case.