Unity 3D: A rough and ready computation of normals - useful for procedural meshes

Here is a rough and ready method to compute a meshes' vertex normals knowing the vertices and the indicies of your mesh.

  List[] normalBuffer= new List[NumVerts];
  
  for(int vl = 0; vl < normalBuffer.Length; ++vl) {
     normalBuffer[vl] = new List();
  }
  
  for( int i = 0; i < NumIndices; i += 3 )
  {
    // get the three vertices that make the faces
    Vector3 p1 = m_original[m_mesh.triangles[i+0]];
    Vector3 p2 = m_original[m_mesh.triangles[i+1]];
    Vector3 p3 = m_original[m_mesh.triangles[i+2]];

    Vector3 v1 = p2 - p1;
    Vector3 v2 = p3 - p1;
    Vector3 normal = Vector3.Cross(v1, v2 );

    normal.Normalize();

    // Store the face's normal for each of the vertices that make up the face.
    normalBuffer[m_mesh.triangles[i+0]].Add(normal);
    normalBuffer[m_mesh.triangles[i+1]].Add(normal);
    normalBuffer[m_mesh.triangles[i+2]].Add(normal);
  }

  for( int i = 0; i < NumVerts; ++i )
  {
   for (int j = 0; j < normalBuffer[i].Count; ++j) {
    m_normals[i] += normalBuffer[i][j];
   }
    
   m_normals[i]  /= normalBuffer[i].Count;
  }