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PhysicalSitmulationExample2

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Physical Sitmalation

One big idea behind the physical simualtion is all the things inside computer is discrete. We should tranfer the smooth/ continuous real world into digit/ discrete/ finite computer language. Instead of having infinite elements(or atoms) in one rope, we are have finite amount of element.

rope

Code

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private void RunScript(bool reset, Point3d anchor0, Point3d anchor1, int nodeCount, double mass, Vector3d gravity, double stiffness, double friction, ref object P, ref object V, ref object C)
  {
    if(reset){
      nodes.Clear();
      vels.Clear();

      Line line = new Line(anchor0, anchor1);
      NurbsCurve lineCurve = line.ToNurbsCurve();

      Point3d[] pts;
      lineCurve.DivideByCount(nodeCount - 1, true, out pts);

      nodes.AddRange(pts);

      for (int i = 0; i < nodeCount; i++)
      {
        vels.Add(new Vector3d(0, 0, 0));
      }
    }

    // Update the location of the anchors
    nodes[0] = anchor0;
    nodes[nodes.Count - 1] = anchor1;



    // Simulation forces for each node
    for (int i = 1; i < nodes.Count - 1; i++)
    {
      Point3d n = nodes[i];
      Vector3d v = vels[i];

      // Calculating all the forces
      Vector3d gravityForce = mass * gravity;
      Vector3d prevSpring = -stiffness * (n - nodes[i - 1]);
      Vector3d nextSpring = -stiffness * (n - nodes[i + 1]);

      // Aggregate all the forces
      Vector3d totalForce = gravityForce + prevSpring + nextSpring;

      // Update velocity
      v += totalForce;

      // Add friction
      v *= friction;

      // Update location of the node
      n += v;

      // Update values on the original lists
      nodes[i] = n;
      vels[i] = v;

    }

    P = nodes;
    V = vels;
    C = new Polyline(nodes);
  }

  // <Custom additional code> 
  List<Point3d> nodes = new List<Point3d>();
  List<Vector3d> vels = new List<Vector3d>();
  // </Custom additional code>