Builder

The Builder is used to construct an immutable surface orientation helper.

Clients provide pointers into their own data, which is synchronously consumed during build(). At a minimum, clients must supply a vertex count. They can supply data in any of the following combinations:

1. normals only ........................... not recommended, selects arbitrary orientation

2. normals + tangents ..................... sign of W determines bitangent orientation

3. normals + uvs + positions + indices .... selects Lengyel's Method

4. positions + indices .................... generates normals for flat shading only

Additionally, the client-side data has the following type constraints:

• Normals must be 3-element float arrays

• Tangents must be 4-element float arrays

• UVs must be 2-element float arrays

• Positions must be 3-element float arrays

• Triangles must be 3-element index arrays (ushort or uint)

Currently, mikktspace is not supported because it requires re-indexing the mesh. Instead we use the method described by Eric Lengyel in "Foundations of Game Engine Development" (Volume 2, Chapter 7).