Normals can point into the object when "difference" is used. Instead of
difference, use intersection, and use "inverse" with the cutting object (torus
in this case).

Margus

Philip Bartol wrote:
> 
> I recently made a top for my lighthouse out of some CGS stuff, a few torus'
> cutting out a couple of cones merged with a sphere and a cone. I originally
> thought about makeing this in sPatch, but it would have generated a bunch of
> patches and I didn't think I needed to be wasting memory and time on such a
> thing.
> 
> I found I could just as easily take a few basic solid shapes and do some math
> on them and make a little CGS object the same way, then I applied a "radial"
> normal to the surface to make it look a little fancier.
> 
> The problem came after my first render of the object. I merged all my objects
> together and applied the single normal to the whole object. The problem is the
> cones that I carved out the torus' with had flipped the normal, what POV
> thought I had was the inside of an object (because of cutting it out with a
> torus).
> 
> My question that I'm pondering is, is there a way to make sure the whole
> object's outsides really are outside, so to speak. My final solution was to
> make two #declare statements defining normals, one with a positive number on
> the radial and the other with a negative. I applied the one with the neg.
> number to the two objects that had been carved out by the torus and the normal
> with the positive value to the rest of the object. My render was fixed, it
> came out correctly, but this is a goofy way to do it.
> 
> I tried all kinds of things to fix this before comming up with this solution,
> doing an intersection with and inverse on the torus.... inverting the final
> difference (which put the camera inside an object)... finally I resorted to
> two normals....
> 
> PHIL
> 
> ---------------------------------------------------

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