VoxelMesh.cs

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

public class VoxelMesh
{
	Mesh mesh;
	Material mat;
	List<Vector3> Points;
	List<Vector3> Verts;
	List<int> Tris;
	List<Vector2> UVs;
	float size = 0.5f;
	public GameObject gameObject;

	public VoxelMesh(Vector3 pos, byte type)
	{
		gameObject = new GameObject();
		gameObject.transform.position = pos;
		Points = new List<Vector3>();
		Points.Add(new Vector3(-size, size,-size));
		Points.Add(new Vector3( size, size,-size));
		Points.Add(new Vector3( size,-size,-size));
		Points.Add(new Vector3(-size,-size,-size));

		Points.Add(new Vector3( size, size, size));
		Points.Add(new Vector3(-size, size, size));
		Points.Add(new Vector3(-size,-size, size));
		Points.Add(new Vector3( size,-size, size));

		Verts = new List<Vector3>();
		Tris = new List<int>();
		UVs = new List<Vector2>();

		CreateMesh(type);
	}

	private void CreateMesh(byte type)
	{
		gameObject.AddComponent("MeshFilter");
		gameObject.AddComponent("MeshRenderer");
		gameObject.AddComponent("MeshCollider");

		switch(type)
		{
			case 0:
				mat = Resources.Load("Materials/Air") as Material;
			break;
			case 1:
				mat = Resources.Load("Materials/Dirt") as Material;
			break;
			case 2:
				mat = Resources.Load("Materials/Stone") as Material;
			break;
			default:
				Debug.LogWarning("Type not available, using default material.");
				mat = Resources.Load("Materials/Default") as Material;
			break;
		}
		if(mat == null)
		{
			Debug.LogError("Material not found!");
			return;
		}

		MeshFilter meshFilter = gameObject.GetComponent<MeshFilter>();
		if(meshFilter == null)
		{
			Debug.LogError("MeshFilter not found!");
			return;
		}

		mesh = meshFilter.sharedMesh;
		if(mesh == null)
		{
			meshFilter.mesh = new Mesh();
			mesh = meshFilter.sharedMesh;
		}

		MeshCollider meshCollider = gameObject.GetComponent<MeshCollider>();
		if(meshCollider == null)
		{
			Debug.LogError("MeshCollider not found!");
			return;
		}

		mesh.Clear();
		UpdateMesh();
	}

	private void UpdateMesh()
	{
		// Front plane
		Verts.Add(Points[0]); Verts.Add(Points[1]); Verts.Add(Points[2]); Verts.Add(Points[3]);
		// Back plane
		Verts.Add(Points[4]); Verts.Add(Points[5]); Verts.Add(Points[6]); Verts.Add(Points[7]);
		// Left plane
		Verts.Add(Points[5]); Verts.Add(Points[0]); Verts.Add(Points[3]); Verts.Add(Points[6]);
		// Right plane
		Verts.Add(Points[1]); Verts.Add(Points[4]); Verts.Add(Points[7]); Verts.Add(Points[2]);
		// Top plane
		Verts.Add(Points[5]); Verts.Add(Points[4]); Verts.Add(Points[1]); Verts.Add(Points[0]);
		// Bottom plane
		Verts.Add(Points[3]); Verts.Add(Points[2]); Verts.Add(Points[7]); Verts.Add(Points[6]);

		// Front Plane
		Tris.Add(0); Tris.Add(1); Tris.Add(2);
		Tris.Add(2); Tris.Add(3); Tris.Add(0);
		// Back Plane
		Tris.Add(4); Tris.Add(5); Tris.Add(6);
		Tris.Add(6); Tris.Add(7); Tris.Add(4);
		// Left Plane
		Tris.Add(8); Tris.Add(9); Tris.Add(10);
		Tris.Add(10); Tris.Add(11); Tris.Add(8);
		// Right Plane
		Tris.Add(12); Tris.Add(13); Tris.Add(14);
		Tris.Add(14); Tris.Add(15); Tris.Add(12);
		// Top Plane
		Tris.Add(16); Tris.Add(17); Tris.Add(18);
		Tris.Add(18); Tris.Add(19); Tris.Add(16);
		// Bottom Plane
		Tris.Add(20); Tris.Add(21); Tris.Add(22);
		Tris.Add(22); Tris.Add(23); Tris.Add(20);

		// Front Plane
		UVs.Add(new Vector2(0,1));
		UVs.Add(new Vector2(1,1));
		UVs.Add(new Vector2(1,0));
		UVs.Add(new Vector2(0,0));
		// Back Plane
		UVs.Add(new Vector2(0,1));
		UVs.Add(new Vector2(1,1));
		UVs.Add(new Vector2(1,0));
		UVs.Add(new Vector2(0,0));
		// Left Plane
		UVs.Add(new Vector2(0,1));
		UVs.Add(new Vector2(1,1));
		UVs.Add(new Vector2(1,0));
		UVs.Add(new Vector2(0,0));
		// Right Plane
		UVs.Add(new Vector2(0,1));
		UVs.Add(new Vector2(1,1));
		UVs.Add(new Vector2(1,0));
		UVs.Add(new Vector2(0,0));
		// Top Plane
		UVs.Add(new Vector2(0,1));
		UVs.Add(new Vector2(1,1));
		UVs.Add(new Vector2(1,0));
		UVs.Add(new Vector2(0,0));
		// Bottom Plane
		UVs.Add(new Vector2(0,1));
		UVs.Add(new Vector2(1,1));
		UVs.Add(new Vector2(1,0));
		UVs.Add(new Vector2(0,0));

		mesh.vertices = Verts.ToArray();
		mesh.triangles = Tris.ToArray();
		mesh.uv = UVs.ToArray();

		Verts.Clear();
		Tris.Clear();
		UVs.Clear();

		MeshCollider meshCollider = gameObject.GetComponent<MeshCollider>();
		mesh.RecalculateNormals();
		mesh.RecalculateBounds();
		RecalculateTangents(mesh);
		meshCollider.sharedMesh = null;
		meshCollider.sharedMesh = mesh;
		gameObject.renderer.material = mat;
		mesh.Optimize();
	}

	private static void RecalculateTangents(Mesh mesh)
	{
		int[] triangles = mesh.triangles;
		Vector3[] vertices = mesh.vertices;
		Vector2[] uv = mesh.uv;
		Vector3[] normals = mesh.normals;

		int triangleCount = triangles.Length;
		int vertexCount = vertices.Length;

		Vector3[] tan1 = new Vector3[vertexCount];
		Vector3[] tan2 = new Vector3[vertexCount];

		Vector4[] tangents = new Vector4[vertexCount];

		for(long a = 0; a < triangleCount; a += 3)
		{
			long i1 = triangles[a];
			long i2 = triangles[a + 1];
			long i3 = triangles[a + 2];

			Vector3 v1 = vertices[i1];
			Vector3 v2 = vertices[i2];
			Vector3 v3 = vertices[i3];

			Vector2 w1 = uv[i1];
			Vector2 w2 = uv[i2];
			Vector2 w3 = uv[i3];

			float x1 = v2.x - v1.x;
			float x2 = v3.x - v1.x;
			float y1 = v2.y - v1.y;
			float y2 = v3.y - v1.y;
			float z1 = v2.z - v1.z;
			float z2 = v3.z - v1.z;

			float s1 = w2.x = w1.x;
			float s2 = w3.x = w1.x;
			float t1 = w2.y = w1.y;
			float t2 = w3.y = w1.y;

			float div = s1 * t2 - s2 * t1;
			float r = div == 0.0f ? 0.0f : 1.0f / div;

			Vector3 sdir = new Vector3((t2 * x1 - t1 * x2) * r, (t2 * y1 - t1 * y2) * r, (t2 * z1 - t1 * z2) * r);
			Vector3 tdir = new Vector3((s1 * x2 - s2 * x1) * r, (s1 * y2 - s2 * y1) * r, (s1 * z2 - s2 * z1) * r);

			tan1[i1] += sdir;
			tan1[i2] += sdir;
			tan1[i3] += sdir;

			tan2[i1] += tdir;
			tan2[i2] += tdir;
			tan2[i3] += tdir;
		}

		for(long a = 0; a < vertexCount; ++a)
		{
			Vector3 n = normals[a];
			Vector3 t = tan1[a];

			Vector3.OrthoNormalize(ref n, ref t);
			tangents[a].x = t.x;
			tangents[a].y = t.y;
			tangents[a].z = t.z;

			tangents[a].w = (Vector3.Dot(Vector3.Cross(n, t), tan2[a]) < 0.0f) ? -1.0f : 1.0f;
		}

		mesh.tangents = tangents;
	}
}