Difference between revisions of "B-splines"

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(New page: The points are connected by a cubic B-spline curve (i.e. order=4). <html><form> <input type="button" value="Add segment" onClick="addSegment();"> <input type="button" value="Remove last s...)
 
Line 7: Line 7:
 
var brd = JXG.JSXGraph.initBoard('jxgbox',{boundingbox:[-4,4,4,-4],keepaspectratio:true,axis:true});
 
var brd = JXG.JSXGraph.initBoard('jxgbox',{boundingbox:[-4,4,4,-4],keepaspectratio:true,axis:true});
  
var p = [];
+
var p = [], col = 'red';  
 
 
var col = 'red';  
 
 
p.push(brd.create('point',[2,1],{strokeColor:col,fillColor:col}));  
 
p.push(brd.create('point',[2,1],{strokeColor:col,fillColor:col}));  
 
p.push(brd.create('point',[0.75,2.5],{strokeColor:col,fillColor:col}));  
 
p.push(brd.create('point',[0.75,2.5],{strokeColor:col,fillColor:col}));  
Line 37: Line 35:
 
   brd.unsuspendUpdate();
 
   brd.unsuspendUpdate();
 
};
 
};
 
 
</jsxgraph>
 
</jsxgraph>
  
Line 44: Line 41:
 
var brd = JXG.JSXGraph.initBoard('jxgbox',{boundingbox:[-4,4,4,-4],keepaspectratio:true,axis:true});
 
var brd = JXG.JSXGraph.initBoard('jxgbox',{boundingbox:[-4,4,4,-4],keepaspectratio:true,axis:true});
  
var p = [];
+
var p = [], col = 'red';
 +
p.push(brd.create('point',[2,1],{strokeColor:col,fillColor:col}));
 +
p.push(brd.create('point',[0.75,2.5],{strokeColor:col,fillColor:col}));
 +
p.push(brd.create('point',[-0.3,0.3],{strokeColor:col,fillColor:col}));
 +
p.push(brd.create('point',[-3,1],{strokeColor:col,fillColor:col}));     
 +
p.push(brd.create('point',[-0.75,-2.5],{strokeColor:col,fillColor:col}));
 +
p.push(brd.create('point',[1.5,-2.8],{strokeColor:col,fillColor:col})); 
 +
p.push(brd.create('point',[2,-0.5],{strokeColor:col,fillColor:col}));  
  
var col = 'red';
+
var c = brd.create('curve', JXG.Math.Numerics.bspline(p,4),  
p.push(brd.create('point',[2,1],{strokeColor:col,fillColor:col}));        // data point
 
col = 'blue';
 
p.push(brd.create('point',[0.75,2.5],{strokeColor:col,fillColor:col}));  // control point
 
p.push(brd.create('point',[-0.3,0.3],{strokeColor:col,fillColor:col}));  // control point
 
 
 
col = 'red';
 
p.push(brd.create('point',[-3,1],{strokeColor:col,fillColor:col}));      // data point
 
col = 'blue';
 
p.push(brd.create('point',[-0.75,-2.5],{strokeColor:col,fillColor:col})); // control point
 
p.push(brd.create('point',[1.5,-2.8],{strokeColor:col,fillColor:col}));  // control point
 
 
 
col = 'red';
 
p.push(brd.create('point',[2,-0.5],{strokeColor:col,fillColor:col}));    // data point
 
 
 
var c = brd.create('curve', JXG.Math.Numerics.bezier(p),  
 
 
               {strokecolor:'blue', strokeOpacity:0.6, strokeWidth:5});  
 
               {strokecolor:'blue', strokeOpacity:0.6, strokeWidth:5});  
  
 
var addSegment = function() {
 
var addSegment = function() {
 
   brd.suspendUpdate();
 
   brd.suspendUpdate();
  col = 'blue';
 
 
   p.push(brd.create('point',[Math.random()*8-4,Math.random()*8-4],
 
   p.push(brd.create('point',[Math.random()*8-4,Math.random()*8-4],
           {strokeColor:col,fillColor:col})); // control point
+
           {strokeColor:col,fillColor:col}));  
  p.push(brd.create('point',[Math.random()*8-4,Math.random()*8-4],
 
          {strokeColor:col,fillColor:col}));  // control point
 
  col = 'red';
 
  p.push(brd.create('point',[Math.random()*8-4,Math.random()*8-4],
 
          {strokeColor:col,fillColor:col}));    // data point
 
 
   brd.unsuspendUpdate();
 
   brd.unsuspendUpdate();
 
};
 
};
Line 80: Line 63:
 
   brd.suspendUpdate();
 
   brd.suspendUpdate();
  
   if (p.length>4) {
+
   if (p.length>2) {
 
       brd.removeObject(p[p.length-1]);
 
       brd.removeObject(p[p.length-1]);
      brd.removeObject(p[p.length-2]);
+
       p.splice(p.length-1,1);
      brd.removeObject(p[p.length-3]);
 
       p.splice(p.length-3,3);
 
 
   }
 
   }
 
   brd.unsuspendUpdate();
 
   brd.unsuspendUpdate();

Revision as of 15:40, 30 July 2010

The points are connected by a cubic B-spline curve (i.e. order=4).

The underlying JavaScript code

var brd = JXG.JSXGraph.initBoard('jxgbox',{boundingbox:[-4,4,4,-4],keepaspectratio:true,axis:true});

var p = [], col = 'red'; 
p.push(brd.create('point',[2,1],{strokeColor:col,fillColor:col})); 
p.push(brd.create('point',[0.75,2.5],{strokeColor:col,fillColor:col})); 
p.push(brd.create('point',[-0.3,0.3],{strokeColor:col,fillColor:col})); 
p.push(brd.create('point',[-3,1],{strokeColor:col,fillColor:col}));      
p.push(brd.create('point',[-0.75,-2.5],{strokeColor:col,fillColor:col}));
p.push(brd.create('point',[1.5,-2.8],{strokeColor:col,fillColor:col}));  
p.push(brd.create('point',[2,-0.5],{strokeColor:col,fillColor:col})); 

var c = brd.create('curve', JXG.Math.Numerics.bspline(p,4), 
               {strokecolor:'blue', strokeOpacity:0.6, strokeWidth:5}); 

var addSegment = function() {
   brd.suspendUpdate();
   p.push(brd.create('point',[Math.random()*8-4,Math.random()*8-4],
           {strokeColor:col,fillColor:col})); 
   brd.unsuspendUpdate();
};

var removeSegment = function() {
   brd.suspendUpdate();

   if (p.length>2) {
       brd.removeObject(p[p.length-1]);
       p.splice(p.length-1,1);
   }
   brd.unsuspendUpdate();
};