Unityで半円柱のMeshを生成するコード

自分用メモ

半円柱のColliderとか作りたい時用。
これで作ったMeshをMeshColliderに設定してあげると、半円状のColliderを作れます。

境界条件などは厳密にテストしておらずバグが確実にあるので、使用する場合は自己責任で

using UnityEngine;
using System.Collections;

public class SemiCircularColumnMeshFactory{
        // 360度の時の、円周の頂点数
	const int MaxPerimeterVertexCount = 20;

	/// <summary>
	/// y軸方向の半円柱のMeshを生成する
	/// </summary>
	/// <returns>Mesh</returns>
	/// <param name="angle">扇の角度</param>
	/// <param name="height">半円柱の高さ</param>
	public static Mesh CreateMesh(float angle,float height) {

		if(angle < 0){
			angle = -angle;
		}
		angle = angle % 360;

		var perimeterVertexCount = (int)( (angle - 0.1f) / (360 / MaxPerimeterVertexCount)) + 2;

		// 頂点計算
		Vector3[] vertices = new Vector3[perimeterVertexCount * 2 + 2];

		var halfHeight = height / 2;

		var currentRadian = -angle / 2 * Mathf.Deg2Rad;
		var deltaRadian = (360 / MaxPerimeterVertexCount)* Mathf.Deg2Rad;

		vertices [0] = new Vector3 (0, halfHeight, 0);
		vertices [perimeterVertexCount + 1] = new Vector3 (0, -halfHeight, 0);

		for(int i = 1;i < perimeterVertexCount;i ++){
			vertices[i] = new Vector3(Mathf.Sin(currentRadian) ,halfHeight,Mathf.Cos(currentRadian));
			vertices[i + perimeterVertexCount + 1] = new Vector3(Mathf.Sin(currentRadian) ,-halfHeight,Mathf.Cos(currentRadian));
			currentRadian += deltaRadian;
		}
		
		vertices[perimeterVertexCount] = new Vector3(Mathf.Sin(angle / 2 * Mathf.Deg2Rad) ,halfHeight,Mathf.Cos(angle / 2 * Mathf.Deg2Rad));
		vertices[perimeterVertexCount * 2 + 1] = new Vector3(Mathf.Sin(angle / 2 * Mathf.Deg2Rad) ,-halfHeight,Mathf.Cos(angle / 2 * Mathf.Deg2Rad));

		var pvc = perimeterVertexCount;

		int fanCount = perimeterVertexCount - 1;
		int offset;
		int[] triangles = new int[ (fanCount * 4 + 4) * 3];
		for (int i = 0; i < perimeterVertexCount - 1; i++) {
			// 上面
			triangles[i * 3] = 0;
			triangles[i * 3 + 1] = i + 1;
			triangles[i * 3 + 2] = i + 2;
			// 底面
			offset = fanCount * 3;
			triangles[offset + i * 3] = pvc + 1;
			triangles[offset + i * 3 + 1] = pvc + 1 + i + 2;
			triangles[offset + i * 3 + 2] = pvc + 1 + i + 1;
			// 円周面1
			offset = fanCount * 3 * 2;
			triangles[offset + i * 3] = i + 2;
			triangles[offset + i * 3 + 1] = i + 1;
			triangles[offset + i * 3 + 2] = pvc + 1 + i + 1;
			// 円周面2
			offset = fanCount * 3 * 3;
			triangles[offset + i * 3] = i + 2;
			triangles[offset + i * 3 + 1] = pvc + 1 + i + 1;
			triangles[offset + i * 3 + 2] = pvc + 1 + i + 2;
		}
		// 側面
		offset = fanCount * 3 * 4;
		triangles [offset] = 1;
		triangles [offset + 1] = 0;
		triangles [offset + 2] = pvc + 1;
		
		triangles [offset + 3] = 1;
		triangles [offset + 4] = pvc + 1;
		triangles [offset + 5] = pvc + 2;
		
		triangles [offset + 6] = 0;
		triangles [offset + 7] = pvc;
		triangles [offset + 8] = pvc + 1;
		
		triangles [offset + 9] = pvc + 1;
		triangles [offset + 10] = pvc;
		triangles [offset + 11] = pvc * 2 + 1;


		Mesh mesh = new Mesh ();
		mesh.name = "SemiCircleCylinder(" + angle + ")";
		mesh.vertices = vertices;
		mesh.triangles = triangles;


		return mesh;

	}



}