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On 10/12/20 7:44 PM, Bald Eagle wrote:
> William F Pokorny <ano### [at] anonymous org> wrote:
>
>> I created quilted test cases and reviewed the shipped demo scenes. A
>> number of other issues popped out. One of which is the 'true normal'
>> results do not match what our documentation shows for quilted normals.
>
> Perhaps I'm wrong or misreading something, but it doesn't appear that the
> documentation properly describes the pattern.
>
> http://wiki.povray.org/content/Reference:Quilted_Pattern
>
> Just looking at the last image,
> "A control value of 1 at both ends will give an "s" shaped curve, resulting in a
> softer, more rounded edge."
> yet the solid line is the s-shaped curve, and it says for that c1 = 0.
>
> After skimming through the source code in patterns and normals, the basic
> formula used to generate the curve seems an awful lot like a specialized form of
> bicubic spline with c0 and c1 influencing the internal two control points...
>
> but it's ... bizarrely different.
> And I can't reproduce the curves and s-shape reliably.
> And I don't know why they don't use a function based on 2*x, or use mod(), ...
>
Yes, I'm not quite sure what's going on there either.
Though I specified defaults of 1 and 1 it looked to me more like 1 and 0
or 0 and 1 depending on how the normals flip on the half unit
intervals... I didn't dive into it. ;-)
One of the complications is the curves as shown have one value inputs.
The result we 'see' is a combination of three applications to three
input values. Ahhh, as I expect you know! :-)
Bill P.
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