BUG: Specular Highlights on Mobile

Hi

attached is an Image that shows the error on Mobile Devices.
The Image is using OpenGL ES3.0 (iOS Metal does have the same problem) and a Standard Shader.(Specular Setup)
I think the Render Pipeline uses BRDF2_Unity_PBS for this setup.
What you can see is the Specular Reflection of a Point Light.

I have done some research and this line does produce the artifacts:

Code (csharp):

1.  
2. float specular = ((specularPower + 1) * pow (nh, specularPower)) / (unity_LightGammaCorrectionConsts_8 * invV * invF + 1e-4f);
3.  

more specific this part:

Code (csharp):

1.  
2. pow (nh, specularPower)
3.  

Replacing this with GPU approximation pow(a,b)=exp2(log2(a)*b) does not resolve this. I think the GPU is using it anyway.
The problem is that when specularPower gets a high value (problem starts at 0.5 roughness or so (specularPower > 1000)) the result of
pow(nh, specularPower) is not "defined". Sometimes it works, sometimes you get a value of zero. I do not know if it is nh dependent.
I changed to code to use floats instead of half but that does not make a difference. Is the precision hardcoded in Unity for Mobile? As I would increase this to find out if this causes the problem.

Can I set the float precision (lowp, mediump, highp) for the builtin shaders? Or better would be a fix from the Unity developers as this happens on Android and iOS, so this should be a problem for many Users.


Thanks in advance

Lutz