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"Allen" <bri### [at] yahoo com> wrote:
> I would like to see the following addition to splines in POV4, support for
> automatic values to create evenly spaced items. If there exists a spline S
> that is an auto-spline, then the distance between any two points on the spline
> S(N*M) and S(N*(M+1)) would be equal. ( S(0.2) - S(0.0) == S(0.4) - S(0.2), and
> so on)
>
> I have currently created a macro that automatically creates a spline from an
> array. It first determines the total distance of points and then creates a
> spline with values ranging from 0.0 to 1.0 based on the distance of any item
> from its start:
>
> #macro auto_spline(_points, _count)
> // First, determine total length of points
> #local cur = 0;
> #local total = 0.0;
> #while(cur < _count - 1)
> #local total = total + vlength(_points[cur + 1] - _points[cur]);
> #local cur = cur + 1;
> #end
> spline
> {
> linear_spline
> #local cur = 0;
> #local accum = 0.0;
> #while(cur < _count - 1)
> accum, _points[cur],
> #local accum = accum + vlength(_points[cur + 1] - _points[cur]) /
> total;
> #local cur = cur + 1;
> #end
> 1.0, _points[cur]
> }
> #end
>
> One idea would to introduce a new keyword 'auto_spline' that behaves much like a
> regular spline, except it is not given values, but only points:
>
> auto_spline
> {
> linear_spline
> <point1>,
> <point2>,
> ...
> <pointN>
> }
>
> That after reading spline elements it would auto-generate the values such that
> the value for any given element is equal to the total distance from that point
> to the first point through all intermediate points, divided by the total spline
> distance. Such a spline would take into consideration that different spline
> types would cause the segments to have different lengths.
Is this related to the thread at
http://news.povray.org/povray.pov4.discussion.general/thread/%3C1v9up3pge5h98h0g5botvjnjj3amvddkgs%404ax.com%3E/?ttop=2
98998
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