Resolved Ability to disable specular highlights for translucent shaders (HDRP)

Hey! As I mentioned in a lot of places already, HDRP added the option to disable the specular highlights in 2022.x but it only works for the Specular shader, making the feature useless for the others. Most developers I talked to, would like to disable the specular on vegetation, which uses the translucent/sss shaders, which doesn't have a specular color field :|

 

Hi. I was wondering if this couldn't be achieved by using the smoothness instead. Disable spec when the smoothness is below 0.02 (2% if I remember correctly) and this would work for all shaders.

 

Thanks for the detailed explanation! It makes much more sense now.

 

I'm obviously a dummy regarding light transport and shading, so please correct me if I'm wrong or missing something, but: this assumes that the geometry is accurately portrayed by the surface normal, right? Which is not really the case for vegetation but also terrain shading (where this causes a lot of headaches, artistically, as well.) I believe there are two major reasons for this:

1. In the above cases, relatively intense normal maps are quite common that tend to break up strong fresnel from up close. However, those normal maps often have more high-and mid frequency detail, which means that at lower mip map levels they tend to be blurred into flatness. The specular issue is especially pronounced at glancing angles and at a distance, both factor which make sampling at lower-res mip levels more common.
2. Both vegetation and terrain materials have their normal maps authored for mostly frontal viewing. However, those types of materials often have considerable depth and complexity 'hidden' within the direction of the surface normal. As a result, the surface normals when viewed from low angles would be considerably different.

I think due to both of these factors, the input to the shading model is using incorrectly & involunatrily flattened surface normal vectors. From my limited understanding, it could be helpful to consider a 'stochastic normal variation' in the fresnel term, particularly at lower mip levels. This could allow artists to correct for the above-mentioned issues and I would argue would also be physically correct.

 

Thanks for the quick response!

Yes, absolutely, this is a good way of adjusting roughness over mip levels. But as you mentioned in this thread, the fresnel response is not tied to the roughness, so a decreased smoothness (or even a smoothness of 0) does not address the issue mentioned in this thread. So I guess what I'm asking about is normal map filtering that attenuates the fresnel response.

Yes, BotD looks excellent and does not have this issue - though it does not feature the situation where, from my experience, this becomes most obvious:

1. LODs of deciduous trees that have large flat triangles that are not spherified, same with 'card' based grass meshes.
2. Open and relatively flat terrains at low sun altitudes.

Corniferous trees, detailed/strand-based ground plant meshes and avoiding large flat areas are great ways of avoiding this issue, though they are not always feasible strategies. With all that said, I'm still aware that the issue of adding a 'fresnel attentuation' is also a technical issue - I just wanted to stress that there are cases where it's not feasible to accurately represent the surface geometry, making the resulting surface look unnatural despite the fresnel response being technically correct for the provided values.

 

Hi, is the trick you mentioned currently usable? Our project has a urgent need to fix the Fresnel issue on puffy tree canopies.