In the post "PBR Materials in Revit" I talked about the workflows in representing the appearance of an object, a space or an architectural project through the renewed ART (Autodesk RayTracer) render engine and the new PBR materials for rendering based on real physics.
Let's now see what shaders are, that is, the algorithms that give the material the characteristics and properties needed to describe how the material reacts in the presence of direct or indirect light.
Revit has four basic categories for its PBR assets. Each has similar options, but differs in that some cannot be edited. These differences will tell RayTracer how the light is supposed to interact with the underlying material. Therefore, knowing these differences will be crucial to getting the most out of your photorealistic render.
The choice of material to apply to your geometry depends on the results you are trying to simulate. For example, light bounces off a metal doorknob very differently than it does off a brick or, even more differently, off window glass.
The starting categories that Revit now offers are:
Metallic.
Metallic materials have or have a fixed amount of *reflectance preset to 1 (100%) that cannot be changed.
This means that with a roughness value of 0 the surface of the material acts like a perfect mirror, higher values will decrease this characteristic.
Non-metallic. A non-metal has a reflectance* value between 0.00 and 0.08 (0-8%).
To represent most non-metallic materials, a value of 0.04 (4%) is sufficient.
Transparent.
Transparent materials have an absorption distance and an index of refraction (IOR) instead of a *reflectance setting. The IOR has a fixed value for different materials and determines how much the light path is refracted or bent when passing through a material. The absorption distance is the distance that light must travel to reach the selected base color of the transparent material. If the thickness of the material remains the same, a shorter absorption distance will result in a darker color, beyond that the color will not change. If the absorption distance is greater than the thickness of the object, the base color will not be reached.
Base and Top Coat. Special materials have a base color with reflections and a top coat with a *reflectance between 0.00 and 1.00 (0 - 100%).
Think of a car paint material, inside Revit. This carbon fiber material underneath has a base color that is black and highlights (specular) that represent the threads or fibers. It has its own roughness and the weight determines the visibility of the specular highlights. The normal map is a standard normal weave. Anisotropy is used so that there is also a checkerboard effect of the weave pattern in this case a simple weave that matches the specular map. The top coat has its own *reflectance (0-1, 0-100%) and roughness. When the *reflectance of the top coat is 100%, you will no longer see the base coat because the top coat acts as a perfect mirror.
(Note that some maps have been resized to make the effects more visible.)
PBR materials in Revit are made up of one of these four basic categories and three values/textures. In the example below the "Cherry" material:
Non-Metal Color / Diffuse (sometimes called Albedo)
Roughness map
Normal / height map, for relief composition
You will find this and other information in the classroom course ADVANCED REVIT 1 • GRAPHIC PRESENTATION OF THE PROJECT, more information can be found HERE . During the course you will be explained the best techniques for creating captivating images and photo-realistic renderings in Revit, by those who have created renderings for the construction industry and for product catalogues (image gallery PINTEREST )
* Reflectance. A measure of the ability of a given surface to reflect part of the incident light.
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