public static Mesh Build(TreeData data, int generations, float length, float radius)
{
data.Setup();
TreeBranch root = new TreeBranch(
generations,
length,
radius,
data
);
List <Vector3> vertices = new List <Vector3>();
List <Vector3> normals = new List <Vector3>();
List <Vector4> tangents = new List <Vector4>();
List <Vector2> uvs = new List <Vector2>();
List <int> triangles = new List <int>();
// 木の全長を取得
// 枝の長さを全長で割ることで、uv座標の高さ(uv.y)が
// 根元から枝先に至るまで[0.0 ~ 1.0]で変化するように設定する
float maxLength = TraverseMaxLength(root);
// 再帰的に全ての枝を辿り、一つ一つの枝に対応するMeshを生成する
Traverse(root, (TreeBranch branch) => {
int offset = vertices.Count;
float vOffset = branch.Offset / maxLength;
float vLength = branch.Length / maxLength;
// 一本の枝から頂点データを生成する
for (int i = 0, n = branch.Segments.Count; i < n; i++)
{
float t = 1f * i / (n - 1);
float v = vOffset + vLength * t;
TreeSegment segment = branch.Segments[i];
Vector3 N = segment.Frame.Normal;
Vector3 B = segment.Frame.Binormal;
for (int j = 0; j <= data.radialSegments; j++)
{
// 0.0 ~ 2π
float u = 1f * j / data.radialSegments;
float rad = u * PI2;
float cos = Mathf.Cos(rad), sin = Mathf.Sin(rad);
Vector3 normal = (cos * N + sin * B).normalized;
vertices.Add(segment.Position + segment.Radius * normal);
normals.Add(normal);
Vector3 tangent = segment.Frame.Tangent;
tangents.Add(new Vector4(tangent.x, tangent.y, tangent.z, 0f));
uvs.Add(new Vector2(u, v));
}
}
// 一本の枝の三角形を構築する
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);
}
}
});
Mesh mesh = new Mesh();
mesh.vertices = vertices.ToArray();
mesh.normals = normals.ToArray();
mesh.tangents = tangents.ToArray();
mesh.uv = uvs.ToArray();
mesh.triangles = triangles.ToArray();
mesh.RecalculateBounds();
return(mesh);
}
protected TreeBranch(int generation, int generations, Vector3 from, Vector3 tangent, Vector3 normal, Vector3 binormal, float length, float radius, float offset, TreeData data)
{
this.generation = generation;
this.fromRadius = radius;
// 枝先である場合は先端の太さが0になる
this.toRadius = (generation == 0) ? 0f : radius *data.radiusAttenuation;
this.from = from;
// 枝先ほど分岐する角度が大きくなる
float scale = Mathf.Lerp(1f, data.growthAngleScale, 1f - 1f * generation / generations);
// normal方向の回転
Quaternion qn = Quaternion.AngleAxis(scale * data.GetRandomGrowthAngle(), normal);
// binormal方向の回転
Quaternion qb = Quaternion.AngleAxis(scale * data.GetRandomGrowthAngle(), binormal);
// 枝先が向いているtangent方向にqn * qbの回転をかけつつ、枝先の位置を決める
this.to = from + (qn * qb) * tangent * length;
this.length = length;
this.offset = offset;
// モデル生成に必要な節を構築
segments = BuildSegments(data, fromRadius, toRadius, normal, binormal);
children = new List <TreeBranch>();
if (generation > 0)
{
// 分岐する数を取得
int count = data.GetRandomBranches();
for (int i = 0; i < count; i++)
{
float ratio; // [0.0 ~ 1.0]
if (count == 1)
{
// 分岐数が1である場合（0除算を回避）
ratio = 1f;
}
else
{
ratio = Mathf.Lerp(0.5f, 1f, (1f * i) / (count - 1));
}
// 分岐元の節を取得
int index = Mathf.FloorToInt(ratio * (segments.Count - 1));
TreeSegment segment = segments[index];
// 分岐元の節が持つベクトルをTreeBranchに渡すことで滑らかな分岐を得る
Vector3 nt = segment.Frame.Tangent;
Vector3 nn = segment.Frame.Normal;
Vector3 nb = segment.Frame.Binormal;
TreeBranch child = new TreeBranch(
this.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
);
children.Add(child);
}
}
}