Assuming yes, in MDL all directional dependencies are reserved for the renderer (to allow for efficient rendering algorithms) and encapsulated in the components we provide for the material definitions. For example, the Fresnel effect is part of the
df::fresnel_factor(…)
or
df::fresnel_layer(…)
There is no direct access to the view or light directions in the render state that you could access from the MDL functions. The state::direction is solely reserved for environment lookups.
Hi, there are also custom curve and measured curve BSDF modifiers that might be more flexible for you. What kind of material are you trying to model in MDL?
In our material, we simply allow to choose different functions to have fresnel effects. And most of them are based directly on the dot product between the normal and the view vector.
But I can see why they left the view vector outside of MDL to be independent from the system.
I will also investigate custom curve and measured curve.