// Editor script that displays the number and UV coordinates of each individual vertex making up a triangle within a mesh
// To install, place in the Assets folder of a Unity project
// Open via Window > Show Vertex Info
// Author: Luke Gane
// Last updated: 2015-02-07

using UnityEditor;
using UnityEngine;

public class ShowVertexNumber : EditorWindow {
	
	Mesh curMesh;
	MeshFilter curMeshFilter;
	SkinnedMeshRenderer curSMR;
	bool meshAvailable = false;
	int curFace = 0, numFaces = 0, newFace = 0;
	
	GUIStyle centredStyle = null;
	
	Vector3 p1, p2, p3;
	
	[MenuItem("Window/Show Vertex Info")]
	public static void ShowWindow(){
		EditorWindow.GetWindow(typeof(ShowVertexNumber)); // Show existing window instance; if one doesn't exist, it is created
	}
	
	void OnEnable(){
		
		// See http://answers.unity3d.com/questions/58018/drawing-to-the-scene-from-an-editorwindow.html
		if (SceneView.onSceneGUIDelegate != this.RenderStuff){ // This appears to be a sufficient check
			SceneView.onSceneGUIDelegate += this.RenderStuff;
		}
		
		OnSelectionChange();
	}
	
	void OnDestroy(){
		SceneView.onSceneGUIDelegate -= this.RenderStuff;
	}
	
	void OnSelectionChange(){
		
		bool noMesh = true;
		
		if (Selection.activeGameObject){
			curMeshFilter = Selection.activeGameObject.GetComponentInChildren<MeshFilter>();
			if (curMeshFilter){
				curMesh = curMeshFilter.sharedMesh;
				meshAvailable = true;
				numFaces = curMesh.triangles.Length/3;
				noMesh = false;
			}
			else{
				curSMR = Selection.activeGameObject.GetComponentInChildren<SkinnedMeshRenderer>();
				if (curSMR){
					curMesh = curSMR.sharedMesh;
					meshAvailable = true;
					numFaces = curMesh.triangles.Length/3;
					noMesh = false;
				}
			}
		}
		
		if (noMesh){
			meshAvailable = false;
			numFaces = 0;
		}
			
		curFace = 0;
		newFace = curFace;
		
		Repaint();
	}
	
	void OnInspectorUpdate(){
		Repaint();
	}
	
	void OnGUI(){
	
		if (meshAvailable){
			
			EditorGUILayout.LabelField("Number of faces: ", numFaces.ToString());
			EditorGUILayout.LabelField("Current face index: ", curFace.ToString());
			
			newFace = EditorGUILayout.IntField("Jump to face index: ", curFace);
			if (newFace != curFace){
				if (newFace >= 0 && newFace < numFaces){
					curFace = newFace;
				}
			}
			
			EditorGUILayout.BeginHorizontal();
			
			if (GUILayout.Button ("Prev Face")){
				curFace = (curFace-1) % numFaces;
				if (curFace < 0){
					curFace = curFace + numFaces;
				}
			}
			
			if (GUILayout.Button ("Next Face")){
				curFace = (curFace+1) % numFaces;
			}
			
			EditorGUILayout.EndHorizontal();
			
			EditorGUILayout.Space();
			
			EditorGUILayout.LabelField("Index of red vertex: ", curMesh.triangles[curFace*3].ToString());
			EditorGUILayout.LabelField("Index of green vertex: ", curMesh.triangles[curFace*3 + 1].ToString());
			EditorGUILayout.LabelField("Index of blue vertex: ", curMesh.triangles[curFace*3 + 2].ToString());
			
			EditorGUILayout.Space();
			
			EditorGUILayout.LabelField("UV coords red vertex: ", "(" + curMesh.uv[curMesh.triangles[curFace*3]].x.ToString() + ", " + curMesh.uv[curMesh.triangles[curFace*3]].y.ToString() + ")");
			EditorGUILayout.LabelField("UV coords green vertex: ", "(" + curMesh.uv[curMesh.triangles[curFace*3 + 1]].x.ToString() + ", " + curMesh.uv[curMesh.triangles[curFace*3 + 1]].y.ToString() + ")");
			EditorGUILayout.LabelField("UV coords blue vertex: ", "(" + curMesh.uv[curMesh.triangles[curFace*3 + 2]].x.ToString() + ", " + curMesh.uv[curMesh.triangles[curFace*3 + 2]].y.ToString() + ")");
		
		}
		else{
			EditorGUILayout.LabelField("Current selection contains no mesh.");
		}
	}
	
	// Analogous to OnSceneGUI message handler of the Editor class
	void RenderStuff(SceneView sceneView){
		if (meshAvailable){
			
			int index1 = curMesh.triangles[curFace*3];
			int index2 = curMesh.triangles[curFace*3 + 1];
			int index3 = curMesh.triangles[curFace*3 + 2];
			
			if (curMeshFilter){
				p1 = curMeshFilter.transform.TransformPoint(curMesh.vertices[index1]);
				p2 = curMeshFilter.transform.TransformPoint(curMesh.vertices[index2]);
				p3 = curMeshFilter.transform.TransformPoint(curMesh.vertices[index3]);
			}
			else if (curSMR){
				p1 = curSMR.transform.TransformPoint(curMesh.vertices[index1]);
				p2 = curSMR.transform.TransformPoint(curMesh.vertices[index2]);
				p3 = curSMR.transform.TransformPoint(curMesh.vertices[index3]);
			}
			
			Handles.color = Color.red;
			Handles.DotCap(0, p1, Quaternion.identity, 0.25f*HandleUtility.GetHandleSize(p1));
			Handles.color = Color.green;
			Handles.DotCap(0, p2, Quaternion.identity, 0.25f*HandleUtility.GetHandleSize(p2));
			Handles.color = Color.blue;
			Handles.DotCap(0, p3, Quaternion.identity, 0.25f*HandleUtility.GetHandleSize(p3));
			
			Handles.color = Color.yellow;
			Handles.DrawDottedLine(p1, p2, 5f);
			Handles.DrawDottedLine(p2, p3, 5f);
			Handles.DrawDottedLine(p3, p1, 5f);
			
			if (centredStyle == null){
				centredStyle = new GUIStyle(GUI.skin.label);
				centredStyle.normal.textColor = Color.black;
				centredStyle.fixedWidth = 40; // If you regularly inspect meshes with more than 999 vertices you may wish to increase this value
				centredStyle.fixedHeight = 20;
				centredStyle.alignment = TextAnchor.MiddleCenter;
				centredStyle.normal.background = Texture2D.whiteTexture; // For reference, whiteTexture is 4x4 (not particularly relevant here)
				centredStyle.fontSize = 12;
				centredStyle.clipping = TextClipping.Overflow;
			}
			
			Handles.Label(p1, index1.ToString(), centredStyle);
			Handles.Label(p2, index2.ToString(), centredStyle);
			Handles.Label(p3, index3.ToString(), centredStyle);
			
			sceneView.Repaint();
		}
	}
	
}