The Fresnel effect is computed as part of the BRDF calculations (a.k.a. However, instead of using a smooth BRDF like Phong or Blinn, it uses a microfacet one.
This is because the Fresnel effect is computed as a function of the angle between the viewing direction and the surface normal, ignoring the directions from which lights illuminate the surfaces.ĪlSurface: This model also uses a two lobe specular model. This model proved to work well in many situations, but at glancing angles, based on the way that it would cut out the SSS, could cause darkening. It also uses Phong as the reflective BRDF. VRay Skin Mtl: This uses a two lobe specular model with a sharp and broad reflection. Diffusion, which preserves more detailed compared to the standard dipole model, and Directional, which allows for an approximation of Single Scatter maps for even greater detail preservation. Vlado has implemented two of them for the V-Ray version of the alSurface shader. It also uses a standard dipole model for the SSS.ĪlSurface: This also has a 3 level depth for the SSS but has weight controls on each one. VRay Skin Mtl: There is a 3 level depth sub surface which is equally blended together. VRay Skin Mtl: Diffuse and Sub-Surface color are actually two different maps and they are blended together by the diffuse amount.ĪlSurface: Diffuse and Sub-Surface color are actually driven by the same map and there is a SSS mix that controls how much that surface is effected by the subsurface scattering versus how much is driven by the Lambertian diffuse. Here is a breakdown of those differences: Diffuse Here is a break down the of the alSurface shader in V-Ray so far:Īs the motivation of the alSurface shader was centered around skin, let us examine how it is different from other skin shaders such as aiSkin shader in Arnold, and the VRay Skin Mrtl, which are in fact very similar in their approach. The only parts that are missing are the refraction and translucency, which may be added at some later point. It takes into account diffuse, 2 levels of specular, and sub surface scattering. He has even created a page dedicated to alShaderĪlShaders site > V-Ray’s first implementation of the alSurface shaderīased on a strong demand from a V-Ray user, Luc Begins, on the V-Ray Forum, and the fact that the shader was now open sourced, Vlado decided to implement parts of the alSurface shader, specifically, all the parts needed to reproduce skin. He recently open sourced the shader itself, allowing others to implement it into their own rendering engines.
His shaders have always been well respected by the industry, however, one element of the alSurface shader that gets a lot of people’s attention is how good it is at reproducing a skin shader.
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