more than one S(t) for curve fitting

lib/curve-fitter.js

@@ -1,6 +1,8 @@
 var invert = require('./matrix-invert.js');
 var matrices = [];
 
+const POLYGONAL = 'polygonal', EQUIDISTANT = 'equidistant';
+
 var binomialCoefficients = [[1],[1,1]];
 
 function binomial(n,k) {
@@ -108,7 +110,9 @@ function computeBasisMatrix(n) {
   return M;
 }
 
-function computeTimeValues(P, n) {
+var computeTimeValues = {};
+
+computeTimeValues[POLYGONAL] = function computePolygonalTimeValues(P, n) {
   n = n || P.length;
   var D = [0];
   for(var i = 1; i<n; i++) {
@@ -119,6 +123,10 @@ function computeTimeValues(P, n) {
   return S;
 }
 
+computeTimeValues[EQUIDISTANT] = function computeEquidistantTimeValues(P, n) {
+  return '0'.repeat(n).split('').map((_,i) =>i/(n-1));
+}
+
 function raiseRowPower(row, i) {
   return row.map(v => Math.pow(v,i));
 }
@@ -150,13 +158,17 @@ function computeBestFit(P, M, S, n) {
   return { x: Cx, y: Cy };
 }
 
-function fit(points) {
+function fit(points, mode) {
+  mode = mode || 0;
+  console.log("mode: ", mode);
   var n = points.length,
       P = Array.from(points),
       M = computeBasisMatrix(n),
-      S = computeTimeValues(P, n),
+      S = computeTimeValues[fit.modes[mode]](P, n),
       C = computeBestFit(P, M, S, n);
   return { n, P, M, S, C };
 }
 
+fit.modes = [ POLYGONAL, EQUIDISTANT];
+
 module.exports = window.makeFit = fit;

lib/site/handlers.js

@@ -2371,14 +2371,23 @@ return {
   reset: function() {
     this.points = [];
     this.curveset = false;
-    let api = this.api;
-    if (api) {
+    this.mode = 0;
+    if (this.api) {
+      let api = this.api;
       api.setCurve(false);
       api.reset();
       api.redraw();
     }
   },
 
+  toggle: function() {
+    if (this.api) {
+      this.mode = (this.mode + 1) % fit.modes.length;
+      this.fitCurve(this.api);
+      this.api.redraw();
+    }
+  },
+
   draw: function(api, curve) {
     api.setPanelCount(1);
     api.reset();
@@ -2387,19 +2396,7 @@ return {
 
     api.setColor('black');
     if (!this.curveset && this.points.length > 2) {
-      let bestFitData = fit(this.points),
-          x = bestFitData.C.x,
-          y = bestFitData.C.y,
-          bpoints = [];
-      x.forEach((r,i) => {
-        bpoints.push({
-          x: r[0],
-          y: y[i][0]
-        });
-      });
-      curve = new api.Bezier(bpoints);
-      api.setCurve(curve);
-      this.curveset = true;
+      this.fitCurve(api);
     }
 
     if (curve) {
@@ -2407,6 +2404,25 @@ return {
       api.drawSkeleton(curve);
     }
     api.drawPoints(this.points);
+
+    api.setFill(0);
+    api.text("using "+fit.modes[this.mode]+" t values", {x: 5, y: 10});
+  },
+
+  fitCurve(api) {
+    let bestFitData = fit(this.points, this.mode),
+        x = bestFitData.C.x,
+        y = bestFitData.C.y,
+        bpoints = [];
+    x.forEach((r,i) => {
+      bpoints.push({
+        x: r[0],
+        y: y[i][0]
+      });
+    });
+    var curve = new api.Bezier(bpoints);
+    api.setCurve(curve);
+    this.curveset = true;
   },
 
   onClick: function(evt, api) {