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I work on a Bezier curve subdivision project. I managed to implement it, but I faced some problems. (The code of my program is presented below.) Firstly, if I change parameter n after changing other manipulators, then my program crashes. (But I can change it in the very beginning.) Secondly, if I change position of 2D-sliders or parameter t after changing positions of locators(red and blue points), then the resulting parts will not be Bezier curves, that's why sliders and parameter t should not be able to move after any change of locators.

That is why I decided to make a Reset Button for Manipulate (or for Dynamic Module?) which will return everything to initial state, from which we can change parameter n without crash. But how can I do that?

Also I want to make 2D-sliders and parameter t motionless(to freeze them) if any change of positions of locators is made. It turned out to be too difficult for me. Please, help. Here is the code of my program:

DynamicModule[
{ pts, pts0,  n, s, (*listoflocs, listoflocsinit,*) part1init,
part2init, divpoint},









listoflocsinit = {};
listoflocsinit = part1init~Join~part2init;

Manipulate[




part1init = {};
part2init = {};



b[t_, i_, r_] := (1 - t) b[t, i, r - 1] + t b[t, i + 1, r - 1];





For[i = 0, i < n - 1, i++, 
b[t_, i, 1] = (1 - t) pts0[[i + 1]] + t pts0[[i + 2]] ];


For[i = 1, i < n - 1, i++,
 part1init = Join[part1init, {b[s, 0, i]}]  ];
For[i = 1, i < n - 1, i++,  
part2init = Join[part2init, {b[s, i, n - 1 - i]} ]   ];


pts = pts0;


divpoint = b[s, 0, n - 1];




Show[
{

Graphics[ {{PointSize[Large], Purple, Point[pts], Blue, 
   Point[ Join[
      Join[{pts[[1]]}, listoflocs[[1 ;; n - 2]] ], {divpoint}][[
     2 ;; n - 1]]],
    Black, Point[divpoint], 
   
   Red, 
   Point[ Join[
      Join[{divpoint},  
       listoflocs[[n - 1 ;; 2 n - 4]]], {pts[[n]]}][[
     2 ;; n - 1]]]}, {PointSize[0.024], Black, Point[divpoint]} }
  ],
Graphics[{
  Green, AbsoluteThickness[2], 
  BezierCurve[pts, SplineDegree -> Length[pts] - 1],
  
  Blue,
   BezierCurve[
   Join[Join[{pts[[1]]}, listoflocs[[1 ;; n - 2]] ], {divpoint}], 
   SplineDegree -> 
    Length[Join[
       Join[{pts[[1]]}, 
        listoflocs[[1 ;; n - 2]] ], {divpoint}]] - 1],
  
  Red,
  BezierCurve[
   Join[Join[{divpoint},  
     listoflocs[[n - 1 ;; 2 n - 4]]], {pts[[n]]}], 
   SplineDegree -> 
    Length[Join[
       Join[{divpoint},  
        listoflocs[[n - 1 ;; 2 n - 4]]], {pts[[n]]}]] - 1]
  }]





},
PlotRange -> {{0, 15}, {-2, 15}}, Axes -> True, ImageSize -> 6 72,
Background -> GrayLevel[.98]],






{n, 4, 20, 1, Appearance -> "Labeled"},

{{s, 0.5, "t"}, 0.01, 1, Appearance -> "Labeled"},


Dynamic[

pts0 = Table[{j - 1/j + 2, j + 1/j}, {j, n}];
Dynamic[pts0];
Table[
With[{i = i}, 
 Slider2D[Dynamic[ pts0[[i]] ], {{0, -2}, {15, 15}}] ], {i, n}]
],





{{listoflocs, listoflocsinit }, Locator, 
LocatorAutoCreate ->  True }




]

]
Improve this question
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3
  • $\begingroup$ Could you break down your problem into smaller portions? Also, where does your code fail at the moment? $\endgroup$
    – MarcoB
    Dec 13, 2022 at 19:19
  • $\begingroup$ Do not use For in Mathematica. $\endgroup$
    – cvgmt
    Dec 14, 2022 at 0:37
  • $\begingroup$ My code fails when I change n after any other manipulator (slider, locator). There is problem with locators and that is why I want to make a refresh Button and to add a freezing option. $\endgroup$
    – jkjfgk
    Dec 14, 2022 at 16:44

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