tangent constraint

web/app/constr/constraints.js

@@ -12,6 +12,8 @@ TCAD.constraints.create = function(name, params, values) {
       return new TCAD.constraints.Parallel(params);
     case "P2LDistance":
       return new TCAD.constraints.P2LDistance(params, values[0]);
+    case "P2LDistanceV":
+      return new TCAD.constraints.P2LDistanceV(params);
     case "P2PDistance":
       return new TCAD.constraints.P2PDistance(params, values[0]);
     case "P2PDistanceV":
@@ -157,6 +159,87 @@ TCAD.constraints.P2LDistance = function(params, distance) {
 
 };
 
+
+TCAD.constraints.P2LDistanceV = function(params) {
+
+  this.params = params;//.slice(0, params.length -1);
+
+  var TX = 0;
+  var TY = 1;
+  var LP1X = 2;
+  var LP1Y = 3;
+  var LP2X = 4;
+  var LP2Y = 5;
+  var D = 6;
+
+  this.error = function() {
+    var x0 = this.p0x(), x1 = this.p1x(), x2 = this.p2x();
+    var y0 = this.p0y(), y1 = this.p1y(), y2 = this.p2y();
+    var dist = this.params[D].get();
+    var dx = x2 - x1;
+    var dy = y2 - y1;
+    var d = Math.sqrt(dx * dx + dy * dy);
+    var area = Math.abs
+    (-x0 * dy + y0 * dx + x1 * y2 - x2 * y1); // = x1y2 - x2y1 - x0y2 + x2y0 + x0y1 - x1y0 = 2*(triangle area)
+    if (d == 0) {
+      return 0;
+    }
+    return (area / d - dist);
+
+  };
+
+  this.p1x = function() {
+    return params[LP1X].get();
+  };
+
+  this.p1y = function() {
+    return params[LP1Y].get();
+  };
+
+  this.p2x = function() {
+    return params[LP2X].get();
+  };
+
+  this.p2y = function() {
+    return params[LP2Y].get();
+  };
+
+  this.p0x = function() {
+    return params[TX].get();
+  };
+
+  this.p0y = function() {
+    return params[TY].get();
+  };
+
+  this.gradient = function(out) {
+    var x0 = this.p0x(), x1 = this.p1x(), x2 = this.p2x();
+    var y0 = this.p0y(), y1 = this.p1y(), y2 = this.p2y();
+    var dx = x2 - x1;
+    var dy = y2 - y1;
+    var d2 = dx * dx + dy * dy;
+    var d = Math.sqrt(d2);
+    var area = -x0 * dy + y0 * dx + x1 * y2 - x2 * y1;
+    out[TX]   = ((y1 - y2) / d);
+    out[TY]   = ((x2 - x1) / d);
+    out[LP1X] = (((y2 - y0) * d + (dx / d) * area) / d2);
+    out[LP1Y] = (((x0 - x2) * d + (dy / d) * area) / d2);
+    out[LP2X] = (((y0 - y1) * d - (dx / d) * area) / d2);
+    out[LP2Y] = (((x1 - x0) * d - (dy / d) * area) / d2);
+    out[D] = -1;
+    
+    for (var i = 0; i < 6; i++) {
+      if (Number.isNaN(out[i])) {
+        out[i] = 0;
+      }
+      if (area < 0) {
+        out[i] *= -1;
+      }
+    }
+  }
+
+};
+
 TCAD.constraints.P2PDistance = function(params, distance) {
 
   this.params = params;

web/app/fetchers.js

@@ -46,6 +46,25 @@ TCAD.TWO.ParametricManager.prototype._fetchPointAndLine = function(objs) {
   return [point, line];
 };
 
+TCAD.TWO.ParametricManager.prototype._fetchArcAndLine = function(objs) {
+
+  var arc = null;
+  var line = null;
+
+  for (var i = 0; i < objs.length; ++i) {
+    if (objs[i]._class == 'TCAD.TWO.Arc') {
+      arc = objs[i];
+    } else if (objs[i]._class == 'TCAD.TWO.Segment') {
+      line = objs[i];
+    }
+  }
+  if (arc == null || line == null) {
+    throw "Illegal Argument. Constraint requires arc and line."
+  }
+
+  return [arc, line];
+};
+
 TCAD.TWO.ParametricManager.prototype._fetchTwoLines = function(objs) {
   var lines = [];
   for (var i = 0; i < objs.length; ++i) {

web/app/main2d.js

@@ -99,9 +99,13 @@ TCAD.App2D = function() {
 
     "R = R" : function() {
       app.viewer.parametricManager.rr(app.viewer.selected);
-    }
+    },
 
+    tangent : function() {
+      app.viewer.parametricManager.tangent(app.viewer.selected);
+    }
   };
+  
   actionsF.add(actions, 'addSegment');
   actionsF.add(actions, 'addArc');
   actionsF.add(actions, 'pan');
@@ -115,6 +119,7 @@ TCAD.App2D = function() {
   actionsF.add(actions, 'P2PDistance');
   actionsF.add(actions, 'Radius');
   actionsF.add(actions, 'R = R');
+  actionsF.add(actions, 'tangent');
   actionsF.open();
 
 };

web/app/parametric.js

@@ -32,6 +32,13 @@ TCAD.TWO.ParametricManager.prototype.perpendicular = function(objs) {
   this.add(new TCAD.TWO.Constraints.Perpendicular(lines[0], lines[1]));
 };
 
+TCAD.TWO.ParametricManager.prototype.tangent = function(objs) {
+  var al = this._fetchArcAndLine(objs);
+  var arc  = al[0];
+  var line  = al[1];
+  this.add(new TCAD.TWO.Constraints.P2LDistanceV( arc.c, line, arc.r ));
+};
+
 TCAD.TWO.ParametricManager.prototype.rr = function(objs) {
   var arcs = this._fetchArcs(objs, 2);
   var prev = arcs[0].r;
@@ -72,7 +79,7 @@ TCAD.TWO.ParametricManager.prototype.p2pDistance = function(objs, promptCallback
   var p = this._fetchTwoPoints(objs);
   var distance = new TCAD.Vector(p[1].x - p[0].x, p[1].y - p[0].y).length();
   var promptDistance = promptCallback("Enter the distance", distance.toFixed(2));
-
+  
   if (promptDistance != null) {
     promptDistance = Number(promptDistance);
     if (promptDistance == promptDistance) { // check for NaN
@@ -296,6 +303,22 @@ TCAD.TWO.Constraints.P2LDistance.prototype.getSolveData = function() {
   return ['P2LDistance', params, [this.d]];
 };
 
+
+TCAD.TWO.Constraints.P2LDistanceV = function(p, l, d) {
+  this.p = p;
+  this.l = l;
+  this.d = d;
+};
+
+TCAD.TWO.Constraints.P2LDistanceV.prototype.getSolveData = function() {
+  var params = [];
+  this.p.collectParams(params);
+  this.l.collectParams(params);
+  params.push(this.d);
+  return ['P2LDistanceV', params];
+};
+
+
 TCAD.TWO.Constraints.P2PDistance = function(p1, p2, d) {
   this.p1 = p1;
   this.p2 = p2;