private static float TraverseMaxLength(TreeBranch branch)
{
float max = 0f;
branch.Children.ForEach(c => {
max = Mathf.Max(max, TraverseMaxLength(c));
});
return(branch.Length + max);
}
private static void Traverse(TreeBranch from, Action <TreeBranch> action)
{
if (from.Children.Count > 0)
{
from.Children.ForEach(child => {
Traverse(child, action);
});
}
action(from);
}
protected TreeBranch(List <TreeBranch> branches, int generation, int generations, Vector3 from, Vector3 tangent, Vector3 normal, Vector3 binormal, float length, float radius, float offset, TreeData data)
{
m_Generation = generation;
m_FromRadius = radius;
m_ToRadius = (generation == 0) ? 0f : radius * data.radiusAttenuation;
m_From = from;
var scale = Mathf.Lerp(1f, data.growthAngleScale, 1f - 1f * generation / generations);
var rotation = Quaternion.AngleAxis(scale * data.GetRandomGrowthAngle(), normal) * Quaternion.AngleAxis(scale * data.GetRandomGrowthAngle(), binormal);
m_To = from + rotation * tangent * length;
m_Length = length;
m_Offset = offset;
m_Segments = BuildSegments(data, m_FromRadius, m_ToRadius, normal, binormal);
branches.Add(this);
m_Children = new List <TreeBranch>();
if (generation > 0)
{
int count = data.GetRandomBranches();
for (int i = 0; i < count; i++)
{
float ratio;
if (count == 1)
{
// for zero division
ratio = 1f;
}
else
{
ratio = Mathf.Lerp(0.5f, 1f, (1f * i) / (count - 1));
}
var index = Mathf.FloorToInt(ratio * (m_Segments.Count - 1));
var segment = m_Segments[index];
Vector3 nt, nn, nb;
if (ratio >= 1f)
{
// sequence branch
nt = segment.Frame.Tangent;
nn = segment.Frame.Normal;
nb = segment.Frame.Binormal;
}
else
{
var rot = Quaternion.AngleAxis(i * 90f, tangent);
nt = rot * tangent;
nn = rot * normal;
nb = rot * binormal;
}
var child = new TreeBranch(
branches,
this.m_Generation - 1,
generations,
segment.Position,
nt,
nn,
nb,
length * Mathf.Lerp(1f, data.lengthAttenuation, ratio),
radius * Mathf.Lerp(1f, data.radiusAttenuation, ratio),
offset + length,
data
);
m_Children.Add(child);
}
}
}
public static Mesh Build(TreeData data, int generations, float length, float radius)
{
data.Setup();
var root = new TreeBranch(
generations,
length,
radius,
data
);
var vertices = new List <Vector3>();
var normals = new List <Vector3>();
var tangents = new List <Vector4>();
var uvs = new List <Vector2>();
var triangles = new List <int>();
float maxLength = TraverseMaxLength(root);
Traverse(root, (branch) => {
var offset = vertices.Count;
var vOffset = branch.Offset / maxLength;
var vLength = branch.Length / maxLength;
for (int i = 0, n = branch.Segments.Count; i < n; i++)
{
var t = 1f * i / (n - 1);
var v = vOffset + vLength * t;
var segment = branch.Segments[i];
var N = segment.Frame.Normal;
var B = segment.Frame.Binormal;
for (int j = 0; j <= data.radialSegments; j++)
{
// 0.0 ~ 2π
var u = 1f * j / data.radialSegments;
float rad = u * PI2;
float cos = Mathf.Cos(rad), sin = Mathf.Sin(rad);
var normal = (cos * N + sin * B).normalized;
vertices.Add(segment.Position + segment.Radius * normal);
normals.Add(normal);
var tangent = segment.Frame.Tangent;
tangents.Add(new Vector4(tangent.x, tangent.y, tangent.z, 0f));
uvs.Add(new Vector2(u, v));
}
}
for (int j = 1; j <= data.heightSegments; j++)
{
for (int i = 1; i <= data.radialSegments; i++)
{
int a = (data.radialSegments + 1) * (j - 1) + (i - 1);
int b = (data.radialSegments + 1) * j + (i - 1);
int c = (data.radialSegments + 1) * j + i;
int d = (data.radialSegments + 1) * (j - 1) + i;
a += offset;
b += offset;
c += offset;
d += offset;
triangles.Add(a); triangles.Add(d); triangles.Add(b);
triangles.Add(b); triangles.Add(d); triangles.Add(c);
}
}
});
var mesh = new Mesh
{
vertices = vertices.ToArray(),
normals = normals.ToArray(),
tangents = tangents.ToArray(),
uv = uvs.ToArray(),
triangles = triangles.ToArray()
};
return(mesh);
}