Tangent vector in view space, computed dynamically from geometry and UV derivatives. Useful for normal mapping without precomputed tangents.

Reference: http://www.thetenthplanet.de/archives/1180

Bitangent vector in view space, computed dynamically from geometry and UV derivatives. Complements the tangentViewFrame for constructing the tangent space basis.

Reference: http://www.thetenthplanet.de/archives/1180