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--- 01_user_documentation:05_object:02_light:12_shaders:05_ward [2026/09/22 12:17] – created Tim
+++ 01_user_documentation:05_object:02_light:12_shaders:05_ward [2026/09/22 12:34] (current) – Tim
@@ Line 1: / Line 1: @@
 ====== Ward ======
+ A shader implementing the anisotropic Ward (1992) reflectance model.
+=====  =====
+The BRDF is:
+$f_r = k_d / π  +  k_s · exp(−E(h)) / (4π · α_u · α_v · √(cos θ_i · cos θ_o))$
+where the exponent for the isotropic case is
+$E(h) = tan²θ_h / α²$
+and for the anisotropic case
+$E(h) = ((h·T)² / α_u²  +  (h·B)² / α_v²) / (h·N)²$
+with N the surface normal, T = dpdu, B = dpdv the surface tangents,
+α_u the roughness along T, and α_v the roughness
+along B if isotropic with α_v = α_u.
+The model supports diffuse, specular, and (optionally) transparent
+transmission via the field. Transmission uses Fresnel-weighted straight-through (delta BTDF), CPU light model only.