generateNormals function

void generateNormals (Vector3List normals, Vector3List positions, Uint16List indices)

Generate vertex normals based on a list of positions and indices. normals is assumed to be zeroed out, and much match positions in length. indices is assumed to represent a triangle list.

Implementation

void generateNormals(
    Vector3List normals, Vector3List positions, Uint16List indices) {
  final Vector3 p0 = new Vector3.zero(),
      p1 = new Vector3.zero(),
      p2 = new Vector3.zero(),
      norm = new Vector3.zero();

  // Loop through every polygon, find it's normal, and add that to the vertex
  // normals.
  for (int i = 0; i < indices.length; i += 3) {
    final int i0 = indices[i], i1 = indices[i + 1], i2 = indices[i + 2];
    positions..load(i0, p0)..load(i1, p1)..load(i2, p2);

    p1.sub(p0);
    p2.sub(p0);

    // Store the normalized cross product of p1 and p2 in p0.
    p1.crossInto(p2, p0).normalize();

    // Add the face normal to each vertex normal.
    normals.load(i0, norm);
    normals[i0] = norm..add(p0);

    normals.load(i1, norm);
    normals[i1] = norm..add(p0);

    normals.load(i2, norm);
    normals[i2] = norm..add(p0);
  }

  // Loop through all the normals and normalize them.
  for (int i = 0; i < normals.length; ++i) {
    normals.load(i, norm);
    normals[i] = norm..normalize();
  }
}