CrowdControl/Assets/Feel/MMTools/Editor/MMCollisions/MMMeshToPolygonCollider2D.cs

using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEditor;
using UnityEditor.SceneManagement;
using UnityEngine;

namespace MoreMountains.Tools
{
	/// <summary>
	/// A class that lets you create polygon collider 2D out of mesh filters
	/// </summary>
	public class MMMeshToPolygonCollider2D : MonoBehaviour
	{
		/// <summary>
		/// Generates a PolygonCollider2D out of a meshfilter
		/// </summary>
		/// <param name="meshFilter"></param>
		private static void GeneratePolygonCollider2D(MeshFilter meshFilter)
		{
			// we validate our mesh
			if (!ValidateMesh(meshFilter))
			{
				return;
			}

			// we grab or create our PolygonCollider2D
			PolygonCollider2D polygonCollider2D = InitializePolygonCollider2D(meshFilter);
			if (polygonCollider2D == null)
			{
				return;
			}

			Vector3[] vectors = MeshFilterToVectors(meshFilter);
			Vector2[] newPoints = VectorsToPoints(vectors);
			EditorUtility.SetDirty(polygonCollider2D);
			polygonCollider2D.SetPath(0, newPoints);
		}

		/// <summary>
		/// Takes an array of vectors and outputs points
		/// </summary>
		/// <param name="vectors"></param>
		/// <returns></returns>
		private static Vector2[] VectorsToPoints(Vector3[] vectors)
		{
			List<Vector2> newColliderVertices = new List<Vector2>();

			for (int i = 0; i < vectors.Length; i++)
			{
				newColliderVertices.Add(new Vector2(vectors[i].x, vectors[i].y));
			}

			Vector2[] newPoints = newColliderVertices.Distinct().ToArray();
			return newPoints;
		}

		/// <summary>
		/// Turns a meshfilter into an array of vectors
		/// </summary>
		/// <param name="meshFilter"></param>
		/// <returns></returns>
		private static Vector3[] MeshFilterToVectors(MeshFilter meshFilter)
		{
			List<Vector3> vertices = new List<Vector3>();
			meshFilter.sharedMesh.GetVertices(vertices);

			List<MMGeometry.MMEdge> boundaryPath = MMGeometry.GetEdges(meshFilter.sharedMesh.triangles).FindBoundary().SortEdges();

			Vector3[] vectors = new Vector3[boundaryPath.Count];
			for (int i = 0; i < boundaryPath.Count; i++)
			{
				vectors[i] = vertices[boundaryPath[i].Vertice1];
			}

			return vectors;
		}

		/// <summary>
		/// Grabs or creates a polygon collider 2D
		/// </summary>
		/// <param name="meshFilter"></param>
		/// <returns></returns>
		private static PolygonCollider2D InitializePolygonCollider2D(MeshFilter meshFilter)
		{
			PolygonCollider2D polygonCollider2D = meshFilter.GetComponent<PolygonCollider2D>();
			if (polygonCollider2D == null)
			{
				polygonCollider2D = meshFilter.gameObject.AddComponent<PolygonCollider2D>();
			}
			polygonCollider2D.pathCount = 1;
			return polygonCollider2D;
		}

		/// <summary>
		/// Makes sure that 
		/// </summary>
		/// <param name="meshFilter"></param>
		/// <returns></returns>
		private static bool ValidateMesh(MeshFilter meshFilter)
		{
			if (meshFilter.sharedMesh == null)
			{
				Debug.LogWarning("[MMMeshToPolygonCollider2D] " 
				                 + meshFilter.gameObject.name 
				                 + " needs to have at least a mesh set on its mesh filter component.");
				return false;
			}
			return true;
		}

		/// <summary>
		/// A method meant to be called via the Tools menu, that will go through all mesh colliders on an object and generate a polygon collider2D out of it
		/// </summary>
		[MenuItem("Tools/More Mountains/Collisions/Generate PolygonCollider2D", false, 601)]
		public static void GeneratePolygonCollider2DMenu()
		{
			Transform activeTransform = Selection.activeTransform;
			if (activeTransform == null)
			{
				Debug.LogWarning("[MMMeshToPolygonCollider2D] You need to select a gameobject first.");
				return;
			}

			EditorSceneManager.MarkSceneDirty(activeTransform.gameObject.scene);
			MeshFilter[] meshFilters = activeTransform.GetComponentsInChildren<MeshFilter>();

			foreach (MeshFilter meshFilter in meshFilters)
			{
				GeneratePolygonCollider2D(meshFilter);                
			}
		}
	}
}