Am 09.04.2015 um 21:01 schrieb clipka:
> Am 09.04.2015 um 18:17 schrieb clipka:
>
>> Yes, this certainly is a bug. I haven't looked at the code yet, but
>> judging from the effect I would assume that the surface normal at a
>> given intersection point is computed as the (normalized) vector from the
>> closest point on the "centroid circle" to the surface point; obviously
>> this breaks down for the inner spindle of a spindle torus.
>
> And that's exactly what's happening.
>
> I've just submitted a fix to GitHub
> (https://github.com/POV-Ray/povray/commit/c3551f249c89ffc817a4deb2acea0412a0b9913f).

BTW, the intention of the new implementation is that a spindle torus 
(one that intersects itself) behaves like a union, i.e.:

- the spindle volume (the volume of self-intersection) is considered to 
be inside the torus

- the spindle surface is visible (provided you find a way to look 
through the regular torus surface), and textured as a straightforward 
continuation of the regular torus surface; most notably, when using an 
interior_texture, the spindle surface's side facing the coordinate 
origin uses the interior_texture, while the other side uses the regular 
texture.

(If someone wants to do me a favor, can you please test whether the UV 
mapping on the spindle surface makes sense.)


Also, specifying either a negative major or minor radius now has the 
same effect as using the "inverse" keyword, but prompts a parse warning. 
(Specifying both a negative major and minor radius negates the effect, 
but will prompt two warnings.)

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