public static Body Tree(this World world, Vector2 origin, int depth, float branchLength, float segmentCoef, float theta)
{
var treeBase = new Vertex(origin);
var root = new Vertex(origin + new Vector2(0, 50));
var vertices = new List <Vertex>();
var constraints = new List <Constraint>();
var desc = new TreeFoliageDesc();
vertices.Add(treeBase);
vertices.Add(root);
var firstBranch = Branch(vertices, constraints, desc, treeBase, 0, depth, segmentCoef, new Vector2(0, -1), branchLength, theta);
constraints.Add(new AngleConstraint(root, treeBase, firstBranch, 1));
// animates the tree at the beginning
var noise = 3;
for (var i = 2; i < vertices.Count; ++i)
{
vertices[i].position += new Vector2(Mathf.Floor(Random.value * noise), 0);
}
var body = new Body(vertices.ToArray(), constraints.ToArray());
body.tag = Tags.Tree;
body.data = desc;
world.AddBody(body);
world.Pins(body, 0, 1);
return(body);
}
private static Vertex Branch(List <Vertex> vertices, List <Constraint> constraints, TreeFoliageDesc desc, Vertex parent, int i, int nMax, float coef, Vector2 normal, float branchLength, float theta)
{
const float lineCoef = 0.7f;
var particle = new Vertex(parent.position + (normal * (branchLength * coef)));
vertices.Add(particle);
if (!(i < nMax))
{
desc.leaves.Add(vertices.Count - 1);
}
var dc = new SpringConstraint(parent, particle, lineCoef);
var distanceFromRootRatio = (float)i / nMax;
constraints.Add(dc);
if (desc.branches.Count < constraints.Count)
{
for (var cIndex = desc.branches.Count; cIndex < constraints.Count; ++cIndex)
{
desc.branches.Add(-1);
}
}
desc.branches[constraints.Count - 1] = distanceFromRootRatio;
if (i < nMax)
{
var a = Branch(vertices, constraints, desc, particle, i + 1, nMax, coef * coef, MathUtils.Rotate(normal, new Vector2(0, 0), -theta), branchLength, theta);
var b = Branch(vertices, constraints, desc, particle, i + 1, nMax, coef * coef, MathUtils.Rotate(normal, new Vector2(0, 0), theta), branchLength, theta);
var jointStrength = Mathf.Lerp(0.7f, 0, distanceFromRootRatio);
constraints.Add(new AngleConstraint(parent, particle, a, jointStrength));
constraints.Add(new AngleConstraint(parent, particle, b, jointStrength));
}
return(particle);
}
