PBR channels in E3D
Element 3D v.2 uses a system of physical shaders (PBR) based on the specular/glossiness duality as opposed to the PBR Disney model, based in metalness/roughness. The big difference between a PBR system and the old systems is the use of specular.
A quality material in this PBR system must have at least 4 inputs: Diffuse, glossiness, reflectivity and normal bump.
Also known as albedo, is the color of the light scattered back from the surface. In other words, it’s the color of the surface without considering other commonly fused effects on this channel as ambient occlusion, lighting, specular or reflection. Colloquially speaking is the texture illuminated by a 100% uniform light.
It is very important to maintain this separation on any directional light or ambient occlusion to achieve a material that suits any light rig. Albedo texture usually has a low contrast usually, maintaining a brightness range between 40-240/255.
Other PBR systems use microsurface or roughness channels with the same role. We have already talk about its importance in the first part of the article in the microsurface section.
In this channel, we are representing the microrelief of a surface. We are indicating in what intensity the current material is matte or gloss, affecting the amplitude and sharpness of specular. White is a shiny surface and black, a completely matte, with all the shades of gray in between.
It is the most difficult map to create since its operation is not «artistic». There is little information on the net on how to create it.
Here we assign the specular color of each of the parts of our object. That color defines the amount of light is immediately reflected by the surface when the light source is directly above it, and the color of that specular.
This map should be fairly flat. As we mentioned in the first part of the article, the reflectivity of a material/substance is constant and is in the glossiness channel where we should represent the changes in the surface. In this channel should appear changes in the type of material/substance itself as rust in metal or a metal worn patina on a non-metallic object.
If we use a map in this channel, the specular color in the reflectivity section must be set to white (255/255/255), since it is multiplied with the values of the map.
As extra information, dielectric materials, although in the second part of this article we would say they were in a range of 0-20%, most don’t exceed 5% reflectivity, leaving at least 2%. Remember, ALL materials reflect.
In this channel we can define the palpable relief on a surface. Small details in this channel can generate some variations in the reflections that give life to materials in a similar way to the glossiness channel. These two channels are closely linked, but either way, keep the micro-scale details in the glossiness channel.
With the other three channels, we can refine the materials and assign some additional properties.
Contact shadows and dirt already baked.
Different enviroment for this single object.
That’s all about the introduction to PBR in E3D v2. With these explanations you should be able to create your PBR materials in Element 3D v2 and recycle maps from other no PBR systems and import materials from previous versions of E3D.
«Feeding a physically based shading model». http://seblagarde.wordpress.com/2011/08/17/feeding-a-physical-based-lighting-mode/
«DONTNOD Physically based rendering chart for Unreal Engine 4». http://seblagarde.wordpress.com/2014/04/14/dontnod-physically-based-rendering-chart-for-unreal-engine-4/
«Basic Theory of Physically-Based Rendering». http://www.marmoset.co/toolbag/learn/pbr-theory
«Tutorial: Physically Based Rendering, And You Can Too!». http://www.marmoset.co/toolbag/learn/pbr-practice
«Tutorial: PBR Texture Conversion». http://www.marmoset.co/toolbag/learn/pbr-conversion