La=ka Ia L_a = k_a \, I_a La=kaIa
Ld=kd Id max(0,n⋅l) L_d = k_d \, I_d \, max(0, \mathbf{n}\cdot \mathbf{l}) Ld=kdIdmax(0,n⋅l)
Ls=ks Is max(0,n⋅h)p L_s = k_s \, I_s \, max(0, \mathbf{n}\cdot \mathbf{h})^p Ls=ksIsmax(0,n⋅h)p
其中 h 是半程向量，定义为
h=v+l∥v+l∥ \mathbf{h} = \frac{\mathbf{v} + \mathbf{l}}{\|\mathbf{v} + \mathbf{l}\|} h=∥v+l∥v+l
