2013-02-25 11:48:30 +00:00
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var Verlet = function(Width, Height)
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{
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this.Masses = [];
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this.Constraints = [];
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this.Width = Width;
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this.Height = Height;
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this.AddMass = function(Mass)
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{
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this.Masses.push(Mass);
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2013-02-25 12:17:55 +00:00
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return Mass;
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}
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this.AddConstraint = function(Constraint)
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{
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this.Constraints.push(Constraint);
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2013-02-25 11:48:30 +00:00
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}
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this.Update = function(TimeDelta)
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{
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2013-02-25 12:17:55 +00:00
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for (k in this.Constraints)
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{
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var c = this.Constraints[k];
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if (typeof(c) == "function")
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continue;
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c.Update(TimeDelta);
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}
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2013-02-25 11:48:30 +00:00
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for (k in this.Masses)
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{
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var m = this.Masses[k];
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if (typeof(m) == "function")
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continue;
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m.Update(TimeDelta, {X: this.Width, Y: this.Height});
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}
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}
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}
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var Mass = function(X, Y, Weight)
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{
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this.Weight = Weight;
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this.PX = this.X = X;
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this.PY = this.Y = Y;
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this.Active = true;
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this.Update = function(TimeDelta, Bounds)
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{
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if (!this.Active)
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return;
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// do a verlet step
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var VX = this.X - this.PX;
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var VY = this.Y - this.PY;
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this.PX = this.X;
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this.PY = this.Y;
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2013-02-25 12:17:55 +00:00
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// shitty air friction
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if (VY > 0)
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VY = VY - TimeDelta
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else
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VY = VY + TimeDelta
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if (VX > 0)
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VX = VX - TimeDelta
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else
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VX = VX + TimeDelta
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2013-02-25 11:48:30 +00:00
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// add gravity (mgt^2/2)
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VY = VY + (this.Weight * (9.98 * (TimeDelta*TimeDelta)) / 2) * 100;
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// add speed to X, Y
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this.X = this.X + VX;
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this.Y = this.Y + VY;
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// console.log(this);
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// limit to bounds
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if (this.Y < 0)
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{
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this.Y = 0;
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this.VY = 0;
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}
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if (this.X < 0)
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{
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this.X = 0;
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this.VX = 0;
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}
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if (this.Y > Bounds.Y)
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{
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this.Y = Bounds.Y;
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this.VY = 0;
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}
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if (this.X > Bounds.X)
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{
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this.X = Bounds.X;
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this.VX = 0;
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}
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}
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}
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2013-02-25 12:17:55 +00:00
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var Constraint = function(Mass1, Mass2)
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{
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this.Mass1 = Mass1;
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this.Mass2 = Mass2;
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this.Distance = Math.sqrt(Math.pow(Mass1.X - Mass2.X, 2) + Math.pow(Mass1.Y - Mass2.Y, 2));
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this.Update = function(TimeDelta)
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{
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var d1 = Math.sqrt(Math.pow(this.Mass1.X - this.Mass2.X, 2) + Math.pow(this.Mass1.Y - this.Mass2.Y, 2));
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var d2 = (d1 - this.Distance) / d1;
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var coefm1;
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var coefm2;
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if (!this.Mass1.Active)
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{
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coefm1 = 0;
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coefm2 = 1;
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}
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else if (!this.Mass2.Active)
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{
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coefm1 = 1;
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coefm2 = 0;
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}
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else
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{
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coefm1 = (this.Mass1.Weight / (this.Mass1.Weight + this.Mass2.Weight));
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coefm2 = (this.Mass2.Weight / (this.Mass1.Weight + this.Mass2.Weight));
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}
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this.Mass1.X = this.Mass1.X - (this.Mass1.X - this.Mass2.X) * d2 * coefm1;
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this.Mass2.X = this.Mass2.X + (this.Mass1.X - this.Mass2.X) * d2 * coefm2;
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this.Mass1.Y = this.Mass1.Y - (this.Mass1.Y - this.Mass2.Y) * d2 * coefm1;
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this.Mass2.Y = this.Mass2.Y + (this.Mass1.Y - this.Mass2.Y) * d2 * coefm2;
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}
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}
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2013-02-25 11:48:30 +00:00
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var v = new Verlet(800, 600);
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2013-02-25 12:17:55 +00:00
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var m1 = v.AddMass(new Mass(5, 5, 1));
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var m2 = v.AddMass(new Mass(55, 100, 1));
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var m3 = v.AddMass(new Mass(105, 5, 1));
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v.AddConstraint(new Constraint(m1, m2));
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v.AddConstraint(new Constraint(m2, m3));
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v.AddConstraint(new Constraint(m1, m3));
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2013-02-25 11:48:30 +00:00
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var c = document.getElementById("main");
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var ctx = c.getContext('2d');
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c.width = 800;
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c.height = 600;
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setInterval(function()
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{
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ctx.fillStyle = '#000000';
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ctx.beginPath();
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ctx.rect(0, 0, 800, 600);
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ctx.closePath();
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ctx.fill();
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v.Update(1/50);
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ctx.fillStyle = '#FFFFFF';
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for (k in v.Masses)
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{
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var m = v.Masses[k];
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if (typeof(m) == "function")
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continue;
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ctx.beginPath();
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ctx.arc(m.X, m.Y, 5, 0, Math.PI*2, true);
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ctx.closePath();
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ctx.fill();
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}
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2013-02-25 12:17:55 +00:00
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ctx.strokeStyle = '#FFFFFF';
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for (k in v.Constraints)
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{
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var c = v.Constraints[k];
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if (typeof(c) == "function")
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continue;
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ctx.beginPath();
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ctx.moveTo(c.Mass1.X, c.Mass1.Y);
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ctx.lineTo(c.Mass2.X, c.Mass2.Y);
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ctx.stroke();
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}
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2013-02-25 11:48:30 +00:00
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}, 1000/50);
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var DragID = -1;
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var DragOffsetX = 0;
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var DragOffsetY = 0;
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var DragMoveListener = function(e)
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{
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var MouseX = e.layerX - c.offsetLeft;
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var MouseY = e.layerY - c.offsetTop;
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var m = v.Masses[DragID]
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m.PX = m.X;
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m.PY = m.Y;
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m.X = MouseX + DragOffsetX;
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m.Y = MouseY + DragOffsetY;
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}
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var DragEndListener = function(e)
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{
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v.Masses[DragID].Active = true;
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DragID = -1;
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c.removeEventListener("mouseup", DragEndListener);
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c.removeEventListener("mousemove", DragMoveListener);
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c.addEventListener("mousedown", DragStartListener);
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}
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var DragStartListener = function(e)
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{
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var MouseX = e.layerX - c.offsetLeft;
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var MouseY = e.layerY - c.offsetTop;
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for (k in v.Masses)
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{
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var m = v.Masses[k];
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if (typeof(m) == "function")
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continue;
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var DX = MouseX - m.X;
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var DY = MouseY - m.Y;
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if (Math.sqrt((DX*DX) + (DY*DY)) < 5)
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{
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DragID = k;
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DragOffsetX = DX;
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DragOffsetY = DY;
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m.Active = false;
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c.removeEventListener("mousedown", DragStartListener);
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c.addEventListener("mousemove", DragMoveListener);
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c.addEventListener("mouseup", DragEndListener);
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}
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}
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}
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c.addEventListener("mousedown", DragStartListener);
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