"ingo" <nomail@nomail> wrote:
> yesbird <sya### [at] gmailcom> wrote:
> > On 15/03/2023 10:47, yesbird wrote:
>
> Cubic splines are hard to compare. What cubic is used by whom?

Cubic B-spline using my curve macros

---%<------%<------%<---

#version 3.7;

#include "curve.inc"  //https://ingoogni.nl/download/Curve.zip

#global_settings{ assumed_gamma 1.0 }
#default{ finish{ ambient 0.1 diffuse 0.9 emission 0}}

#declare Bspl3 = CIbspline3(
    array[7]{
        <0.000000, -1.000000,0>
        <1.500000, 0.000000,0>
        <0.000000, 1.000000,0>
        <-1.500000, 0.000000,0>
        <0.000000, -1.000000,0>
        <1.500000, 0.000000,0>
        <0.000000, 1.000000,0>
    }
)

//get the points on the curve
#for(T, 0, 1, 0.005)
  sphere{CIget(Bspl3, T), 0.02 pigment{rgb 1}}
#end

//control points
sphere{Bspl3[1][0] 0.03 pigment{rgb <1,0,0>}}
#for(i, 1, dimension_size(Bspl3[1],1) - 1)
  sphere{Bspl3[1][i] 0.03 pigment{rgb <1,0,0>}}
  cylinder{Bspl3[1][i-1], Bspl3[1][i], 0.01 pigment{rgb <1,0,0>}}
#end

camera {
  perspective angle 45
  location  <0, 0, -6>
  right     x*image_width/image_height
  look_at   <0, 0, 0.0>
}

light_source{<0, 0,-3000> color rgb 1}

---%,------%<------%<---

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