Basic verlet integrator.

2013-02-25 12:48:30 +01:00 · 2013-02-25 12:48:30 +01:00 · 89117810cb
commit 89117810cb
2 changed files with 163 additions and 0 deletions
--- a/main.html
+++ b/main.html
@ -0,0 +1,9 @@
+<html>
+    <head>
+        <title>Switchboard</title>
+    </head>
+    <body>
+        <canvas id="main"/>
+        <script type="text/javascript" src="main.js"></script>
+    </body>
+</html>
--- a/main.js
+++ b/main.js
@ -0,0 +1,154 @@
+var Verlet = function(Width, Height)
+{
+    this.Masses = [];
+    this.Constraints = [];
+
+    this.Width = Width;
+    this.Height = Height;
+
+    this.AddMass = function(Mass)
+    {
+        this.Masses.push(Mass);
+    }
+
+    this.Update = function(TimeDelta)
+    {
+        for (k in this.Masses)
+        {
+            var m = this.Masses[k];
+            if (typeof(m) == "function")
+                continue;
+
+            m.Update(TimeDelta, {X: this.Width, Y: this.Height});
+        }
+    }
+}
+var Mass = function(X, Y, Weight)
+{
+    this.Weight = Weight;
+    this.PX = this.X = X;
+    this.PY = this.Y = Y;
+    this.Active = true;
+    this.Update = function(TimeDelta, Bounds)
+    {
+        if (!this.Active)
+            return;
+        // do a verlet step
+        var VX = this.X - this.PX;
+        var VY = this.Y - this.PY;
+        this.PX = this.X;
+        this.PY = this.Y;
+
+        // add gravity (mgt^2/2)
+        VY = VY + (this.Weight * (9.98 * (TimeDelta*TimeDelta)) / 2) * 100;
+
+        // add speed to X, Y
+        this.X = this.X + VX;
+        this.Y = this.Y + VY;
+        // console.log(this);
+
+        // limit to bounds
+        if (this.Y < 0)
+        {
+            this.Y = 0;
+            this.VY = 0;
+        }
+        if (this.X < 0)
+        {
+            this.X = 0;
+            this.VX = 0;
+        }
+        if (this.Y > Bounds.Y)
+        {
+            this.Y = Bounds.Y;
+            this.VY = 0;
+        }
+        if (this.X > Bounds.X)
+        {
+            this.X = Bounds.X;
+            this.VX = 0;
+        }
+    }
+}
+
+var v = new Verlet(800, 600);
+v.AddMass(new Mass(5, 5, 1));
+v.AddMass(new Mass(20, 5, 1));
+v.AddMass(new Mass(35, 5, 1));
+
+var c = document.getElementById("main");
+var ctx = c.getContext('2d');
+c.width = 800;
+c.height = 600;
+
+setInterval(function()
+{
+    ctx.fillStyle = '#000000';
+    ctx.beginPath();
+    ctx.rect(0, 0, 800, 600);
+    ctx.closePath();
+    ctx.fill();
+
+    v.Update(1/50);
+
+    ctx.fillStyle = '#FFFFFF';
+    for (k in v.Masses)
+    {
+        var m = v.Masses[k];
+        if (typeof(m) == "function")
+            continue;
+
+        ctx.beginPath();
+        ctx.arc(m.X, m.Y, 5, 0, Math.PI*2, true);
+        ctx.closePath();
+        ctx.fill();
+    }
+}, 1000/50);
+
+
+var DragID = -1;
+var DragOffsetX = 0;
+var DragOffsetY = 0;
+var DragMoveListener = function(e)
+{
+    var MouseX = e.layerX - c.offsetLeft;
+    var MouseY = e.layerY - c.offsetTop;
+    var m = v.Masses[DragID]
+    m.PX = m.X;
+    m.PY = m.Y;
+    m.X = MouseX + DragOffsetX;
+    m.Y = MouseY + DragOffsetY;
+}
+var DragEndListener = function(e)
+{
+    v.Masses[DragID].Active = true;
+    DragID = -1;
+    c.removeEventListener("mouseup", DragEndListener);
+    c.removeEventListener("mousemove", DragMoveListener);
+    c.addEventListener("mousedown", DragStartListener);
+}
+var DragStartListener = function(e)
+{
+    var MouseX = e.layerX - c.offsetLeft;
+    var MouseY = e.layerY - c.offsetTop;
+    for (k in v.Masses)
+    {
+        var m = v.Masses[k];
+        if (typeof(m) == "function")
+            continue;
+
+        var DX = MouseX - m.X;
+        var DY = MouseY - m.Y;
+        if (Math.sqrt((DX*DX) + (DY*DY)) < 5)
+        {
+            DragID = k;
+            DragOffsetX = DX;
+            DragOffsetY = DY;
+            m.Active = false;
+            c.removeEventListener("mousedown", DragStartListener);
+            c.addEventListener("mousemove", DragMoveListener);
+            c.addEventListener("mouseup", DragEndListener);
+        }
+    }
+}
+c.addEventListener("mousedown", DragStartListener);