On 10/23/25 09:51, Bald Eagle wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:
>> William F Pokorny <ano### [at] anonymousorg> wrote:
>>
>>> 1) I cannot find 'D = ray.Direction;' in my yuqk code? Where and in what
>>> version of source code are you seeing this?
>>
>> Right because that line is not explicitly there.
>> D is implicitly defined as the ray direction.
>>
>> Then in line 256 we do:    len = D.length();
>>
>> Which is why we need to get rid of the y component for reasons explained.
>>
>> So really what we need is an extra line that REdefines the _projected_ ray
>> direction as D = <D.x, 0, D.y> before that length and normalization take place.
>>
>> - BW
> 
> https://news.povray.org/web.68e8688f251da1bc1f9dae3025979125%40news.povray.org
> 
> "2. The issue (*) above was a result of the ray direction being used as-is.
> When I had an angled ray, the length was too large, and overly shortened my
> perpendicular vector.
> When I only used the ray projection onto the xz plane, all of my perpendicular
> vectors were of the proper length."
> 

Thanks Bill.

I think the normalization - including y - is necessary for other reasons 
like the generation of the polynomials, but I also believe I see your 
point about what is needed for the initial bounding cylinder check, 
specifically. I'll try with branch-off code which drops the 'y' 
component for the initial cylinder test only.

Aside: I'd make a moderate bet this tangled with the issues I had in 
some rotation about x tests where parts (partial segments/intervals) of 
the sor would drop out. IIRC, those tests included negative on curve 
(between end control points, points). We'll see.

Bill P.

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