internal Arm(ConstantSet constants, ArmSpec spec)
{
IList <NodePairSpec> nodePairs = spec.NodePair;
NodeSpec upperFirstSpec = nodePairs[0].Upper;
NodeSpec lowerFirstSpec = nodePairs[0].Lower;
DominatedNode lowerFirst = new DominatedNode(lowerFirstSpec.Mass, Vector2D.FromDuple(lowerFirstSpec.Position), Vector2D.FromDuple(lowerFirstSpec.Velocity));
Node upperFirst = new RotationDominantNode(upperFirstSpec.Mass, Vector2D.FromDuple(upperFirstSpec.Position), Vector2D.FromDuple(upperFirstSpec.Velocity), lowerFirst);
UpperNodes = Enumerable
.Repeat(upperFirst, 1)
.Concat(nodePairs.Skip(1).Select(np => new Node(np.Upper)))
.ToArray();
LowerNodes = Enumerable
.Repeat(lowerFirst as Node, 1)
.Concat(nodePairs.Skip(1).Select(np => new Node(np.Lower)))
.ToArray();
Nodes = UpperNodes.Concat(LowerNodes).ToArray();
Compartments = UpperNodes
.Select((node, index)
=> (index == 0) ? null : new Compartment(constants, UpperNodes[index - 1], UpperNodes[index], LowerNodes[index], LowerNodes[index - 1]))
.Skip(1)
.ToArray();
}
/// <summary>
/// Constructs a node constrained to rotate about a center of rotation
/// determined as the midpoint between the initial position and the initial
/// position of the dominated node.
/// </summary>
/// <param name="initialPosition"> </param>
/// <param name="initialVelocity"> </param>
/// <param name="other">
/// The dominated node that will stay at 180 degrees... </param>
public RotationDominantNode(double mass, Vector2D initialPosition, Vector2D initialVelocity, DominatedNode otherNode)
: base(mass, initialPosition, initialVelocity)
{
other = otherNode;
center = initialPosition.Add(otherNode.Position).Scale(0.5);
Vector2D fromCenter = initialPosition.Subtract(center);
radius = fromCenter.Norm;
angle = Math.Atan2(fromCenter.PositionY, fromCenter.PositionX);
angularVelocity = 0;
}