Creating Physically Based Rendering (PBR) Materials

    

Photorealism in 3D-rendered media is both craftsmanship and engineering led by the entertainment industry. To enhance architecture visualization, our team learned the value of materials in a rendering pipeline.

While a computer renders an image of a 3D model, it simulates the interaction between light rays and surfaces. If a job does not require real time display, the images will almost always be manually post-processed to bring out the best quality. But as virtual reality, augmented reality, and mixed reality emerge, there is a major demand for real time rendering. When post-processing is no longer the option, all the effort can only be applied to the preparation of a 3D model, to be more accurate, a scene. One of the greatest results of this endeavor is the design process of physically based rendering (PBR) material.

dblab-house-1

A PBR material is able to simulate any characteristics (e.g. metallic, matte finish) when interacting with light. Such material achieves photorealism using at least four types of maps layered onto each that represent different properties. The diffuse map is the actual color of a material, the normal map shows bumps and dents, the specular map reflects light, and the glossiness map makes smooth or rough surfaces. Besides transparency, these four maps are sufficient to describe the visual character of any material. In a virtual environment, PBR materials react to light well enough such that a mood of a scene can be altered merely by changing the light source. 

dblab-house-2
Light simulation in modern rendering engines is well-developed but creating a material from scratch still requires utter attention to detail. When building a scene for architecture visualization, specificity is important for both the client and the artist. To create a material, multiple references are needed from various manufacturer to gain an objective understanding of the the material in real life. In the case here, the specified wall veneer mimics the look of "fumed eucalyptus." The reference images of eucalyptus show the basic wood pattern unlike common trees, there are vertical striations interrupted by alternating pattern, almost checkerboard-like, traversing horizontally but also at a slight angle.

 fumed eucalyptus reference

pbr procedure

pbr steps

Just by describing the major visual cues on reference images, we break down the material into simple patterns. Creating the material in procedures allows us to focus on one detail at a time. Each step along the way are recorded and may be altered individually without scrapping the outcome. Starting with the most obvious, (1) striations on the fumed eucalyptus veneer can be represented by slightly warped vertical lines in various width. (2) Then an offset checkerboard is combined with the striation, but it still appears too uniformed to be organic. (3) So a randomized stain overlays the previously combined patterns. Note that the pattern, up to this point, is still black and white, (4) because gradient mapping is more effective with more levels of shades than fewer. (5) In the final step, a generic wood grain underlays the main eucalyptus pattern for subtle yet important distinction from flat smooth surfaces. (6) The result of the entire procedure is a collection of maps for one PBR material that can be reused in any scene using any rendering engine.

eucaplyptus final

About The Author

Director of Research and Development