.. _plugin-bsdf-hapke:

Hapke surface model (:monosp:`hapke`)
-------------------------------------

The model uses 6 parameters:

 * - w
   - |spectrum| or |texture|
   - :math:`0 \le w \le 1`.
   - |exposed| |differentiable|

 * - b
   - |spectrum| or |texture|
   - :math:`0 \le w \le 1`.
   - |exposed| |differentiable|

 * - c
   - |spectrum| or |texture|
   - :math:`0 \le w \le 1`.
   - |exposed| |differentiable|

 * - theta (degree)
   - |spectrum| or |texture|
   - :math:`0 \le w \le 90`.
   - |exposed| |differentiable|

 * - B_0
   - |spectrum| or |texture|
   - :math:`0 \le w \le 1`.
   - |exposed| |differentiable|

 * - h
   - |spectrum| or |texture|
   - :math:`0 \le w \le 1`.
   - |exposed| |differentiable|

Implement the Hapke BSDF model as proposed by Bruce Hapke in 1984
(https://doi.org/10.1016/0019-1035(84)90054-X).

All parameters are required.