Violating law of reflection for complex materials

Unity Engine
1

I was looking around on the internet and saw that people were having a problem creating an accurate hair shader. It is is because hair is complex and has transmittance and reflections which come from two different sides of the hair.

this information comes from Marschner’s specular model.
more info (Physically based) Hair shading - Graphics and GPU Programming - GameDev.net
https://www.cs.cornell.edu/~srm/publications/SG03-hair.pdf

I though that this model could be approximated by changing the reflected light angle for multiple passes. Then I thought that this could be used to fake transmission by reflecting light more than 180 degrees.
What I trying to do is create a shader that can reflect light in directions that violate the reflection law which states that the angle of reflection is the same as the angle of incoming light.
I tried to do this by modifying the Phong model with _reflectAng which is between -0.5 and 0.5

half3 vectorA = (2*normalDirection*(NdotL*_reflectAng))-i.lightDir.xyz;

half3 RefVector = i.lightDir.xyz-vectorA;
float specTmp = max(dot(RefVector, i.cameraView), 0.0);
float specularIntensity = pow(specTmp,_Mattelight);

and I also tried

half3 vectorA = i.lightDir.xyz-(normalDirection*(NdotL*_reflectAng));

half3 RefVector = normalize(vectorA-(normalDirection*NdotL));
float specTmp = max(dot(RefVector, i.cameraView), 0.0);
float specularIntensity = pow(specTmp,_Mattelight);

All any of them do is change specularity size. In the second one specularity looks inverted. Maybe I need to apply normal Phong then move the highlight location later. But I have no idea how to do that.

If reflection direction can be controlled then true refraction, strange mirrors and hair should be possible?

2

Transmission is already faked by taking the absolute of the lambert (normal dot light, which illuminate the penumbra), people have been toying with this idea already, wrap light is precisely that, and you would have more success tweaking the normal to do that cheaply. Phong are actually relative to view, I don’t know you will have what you expect.

3

I don’t think I understand you. This has nothing to do with diffuse light, It’s not mentioned in the picture above.
warped lighting would be roughness of a diffuse light. Transmission is related to diffraction.
here is a picture which might help

https://app.box.com/representation/file_version_112583110087/image_2048/1.png
sorry my go to photobucket is down!