ProjectBall.Unity/Assets/Scripts/AdvancedUtils.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System;

public static class AdvancedUtils {

	public static GameObject CreateMeshObject(string name){
		GameObject result = new GameObject(name);
		MeshFilter meshFilter = (MeshFilter)result.AddComponent(typeof(MeshFilter));
		result.AddComponent(typeof(MeshRenderer));
		
		Mesh m = new Mesh();
		m.name = result.name;
		meshFilter.sharedMesh = m;
		return result;
	}

	public static GameObject CreateMeshObject(){
		return CreateMeshObject ("Unnamed object");
	}

	public static void GenerateCylinder(float radius, float length, int sides, int heightSegments,float uTile, float vTile, out Vector3[] vertices, out int[] indices, out Vector2[] uvs, out Vector3[] normals){
		float yBottom = 0.0f;
		Vector3 up = Vector3.up;
		int ringVertexCount = (sides + 1);
		int ringCount = heightSegments + 1;
		int vertexCount = ringCount * ringVertexCount;
		vertices = new Vector3[vertexCount];
		uvs = new Vector2[vertices.Length];
		normals = new Vector3[vertices.Length];

		//generate vertices
		for (int i = 0; i < ringVertexCount; ++i) {
			float angle = ((Mathf.PI * 2.0f) / (float)sides) * (float)(i);
			normals[i] = new Vector3(Mathf.Cos(angle), 0.0f, Mathf.Sin(angle));
			vertices[i] = new Vector3(normals[i].x * radius, yBottom, normals[i].z * radius);
			uvs[i] = new Vector2(((1.0f / (float)sides) * (float)i) * uTile, vTile);
		}

		for (int i = 1; i < ringCount; ++i) {
			float ringY = (length / (float)heightSegments) * (float)i;
			int ringVertexOffset = ringVertexCount * i;
			for (int j = 0; j < ringVertexCount; ++j) {
				vertices[ringVertexOffset + j] = vertices[j];
				vertices[ringVertexOffset + j].y = ringY;
				uvs[ringVertexOffset + j] = new Vector2(uvs[j].x, (1.0f - ((1.0f / (float)heightSegments) * (float)i)) * vTile);
				normals[ringVertexOffset + j] = normals[j];
			}
		}

		//generate indices
		int triangleCount = (2 * sides) * heightSegments;
		indices = new int[triangleCount * 3];
		int idOffset = 0;
		for (int i = 0; i < heightSegments; ++i) {
			int segmentVertexOffset = i * ringVertexCount;
			int nextSegmentVertexOffset = (i + 1) * ringVertexCount;

			for (int j = 0; j < sides; ++j) {
				int sideOffset = segmentVertexOffset + j;

				indices[idOffset + 0] = segmentVertexOffset + j;
				indices[idOffset + 2] = nextSegmentVertexOffset + j + 1;
				indices[idOffset + 1] = nextSegmentVertexOffset + j;

				indices[idOffset + 3] = segmentVertexOffset + j;
				indices[idOffset + 5] = segmentVertexOffset + j + 1;
				indices[idOffset + 4] = nextSegmentVertexOffset + j + 1;

				idOffset+=6;
			}
		}
	}

	public static int[] cubeIndices = new int[]{
		3,2,7,
		7,2,6,
		1,0,5,
		0,4,5,
		0,1,2,
		0,2,3,
		4,6,5,
		4,7,6,
		0,3,4,
		3,7,4,
		2,1,6,
		1,5,6
	};

	public static Vector3[] cubeVertices = new[]{
		new Vector3(-0.5f, 0.5f, -0.5f),
		new Vector3(-0.5f, 0.5f, 0.5f),
		new Vector3(0.5f, 0.5f, 0.5f),
		new Vector3(0.5f, 0.5f, -0.5f),
		new Vector3(-0.5f, -0.5f, -0.5f),
		new Vector3(-0.5f, -0.5f, 0.5f),
		new Vector3(0.5f, -0.5f, 0.5f),
		new Vector3(0.5f, -0.5f, -0.5f),
	};

	public static void CreateMeshCube(Matrix4x4 matrix, out Vector3[] vertices, out int[] indices){
		indices = new int[cubeIndices.Length];
		Array.Copy (cubeIndices, indices, cubeIndices.Length);

		int vertexCount = cubeVertices.Length;
		vertices = new Vector3[vertexCount];
		for (int i = 0; i < vertexCount; ++i) {
			vertices[i] = matrix.MultiplyPoint3x4(cubeVertices[i]);
		}
	}


	public static GameObject FindChild(GameObject parent, string childName){
		if (parent == null) {
			return null;
		}
		var tf = parent.transform.FindChild (childName);
		return tf == null ? null : tf.gameObject;
	}

	public static List<Vector3> CutMesh(Vector3[] vertices, int[] indices, Plane p){
		List<Vector3> cuttedTriangles = new List<Vector3> ();
		
		int cut = 0;
		int notCut = 0;
		
		bool[] sideFlags = new bool[3];
		
		for (int i = 0; i < indices.Length; i+=3) {
			int outside = 0;
			int lastOutsideId = 0;
			int lastInsideId = 0;
			for(int j = 0; j < 3; ++j){
				sideFlags[j] = p.GetSide(vertices[indices[i + j]]);
				if(sideFlags[j]){
					outside++;
					lastOutsideId = j;
				}else{
					lastInsideId = j;
				}
			}
			
			if(	outside ==3){
				notCut++;
			}else{
				cut++;
			}
			
			switch(outside)
			{
			case 0:
				for(int j = 0; j < 3; ++j){
					cuttedTriangles.Add(vertices[indices[i + j]]);
				}
				break;
			case 1:
			{
				Vector3 v0 = vertices[indices[i + lastOutsideId]];
				Vector3 v1 = vertices[indices[i + (lastOutsideId + 1) % 3]];
				Vector3 v2 = vertices[indices[i + (lastOutsideId + 2) % 3]];
				
				float d0 = p.GetDistanceToPoint(v0);
				float d1 = p.GetDistanceToPoint(v1);
				float d2 = p.GetDistanceToPoint(v2);
				
				float a = d0 / (d0 - d1);
				float b = d0 / (d0 - d2);
				
				Vector3 v3 = v0 + (v1 - v0) * a;
				Vector3 v4 = v0 + (v2 - v0) * b;
				
				
				cuttedTriangles.Add(v2);
				cuttedTriangles.Add(v4);
				cuttedTriangles.Add(v3);
				
				cuttedTriangles.Add(v2);
				cuttedTriangles.Add(v3);
				cuttedTriangles.Add(v1);
			}
				break;
			case 2:
			{
				Vector3 v0 = vertices[indices[i + lastInsideId]];
				Vector3 v1 = vertices[indices[i + (lastInsideId + 1) % 3]];
				Vector3 v2 = vertices[indices[i + (lastInsideId + 2) % 3]];
				
				float d0 = p.GetDistanceToPoint(v0);
				float d1 = p.GetDistanceToPoint(v1);
				float d2 = p.GetDistanceToPoint(v2);
				
				float a = d0 / (d0 - d1);
				float b = d0 / (d0 - d2);
				
				Vector3 v3 = v0 + (v1 - v0) * a;
				Vector3 v4 = v0 + (v2 - v0) * b;
				
				cuttedTriangles.Add(v0);
				cuttedTriangles.Add(v3);
				cuttedTriangles.Add(v4);
				
			}
				break;
			}
		}
		return cuttedTriangles;
	}

	/**/
}