In this video, learn how to apply physically plausible shading.
- [Instructor] The success of any rendering depends in part on the materials or shading applied to objects. For non-photo real renderings such as technical drawings, the stylized effect of the render sometimes overwhelms the materials, but materials are always important. If you have expectations of photorealism, then you'll need to become fluent in building physically based materials. The greatest realism in rendering comes from accurate simulations of light propagation or global illumination.
The accuracy of GI rendering depends on accurate simulation of real world material properties such as light absorption, reflection, and transmission. Previous generations of 3D rendering algorithms did not accurately model the physical properties of light and materials. Artists and designers were forced to use strange tricks to make their renders look plausible. But now with Physically Based Rendering, or PBR, our task is much simpler. We design materials according to physical properties and achieve photorealistic results under any lighting conditions.
Different renderers have different implementation of PBR materials, but always include a base color, reflections, and transmission. The base color is sometimes known as the diffuse component or albedo. This is the light that is scattered as it's reflected from a rough or a matte finish surface. A rough surface absorbs all light except the base color which is reflected back to the camera and the scene. The intensity and color of diffused reflections or bounce light is determined by the base color.
For example, a red carpet reflects red bounce light onto a white wall. This is sometimes called color bleed. The reflective component of the material controls the way light scatters when it reflects from a surface. A defining characteristic of physical materials is a parameter for roughness. This is a shading attribute that models microscopic surface roughness to control the amount of diffuse scattering. Roughness sets the balance between diffusion and coherent reflection of light as it bounces off a surface.
Low roughness produces a smooth, glossy, shiny surface. Increase the roughness to simulate a porous or unfinished surface with softer highlights. At its maximum value of one, roughness results in a completely matte finish with no visible highlight. Another common attribute in physically based materials is metalness. As the name implies, it's an extent to which the material simulates the properties of a metal. Metals have greater reflectivity in general than non metals.
But shiny metals have little or no diffuse component. The metalness parameter sets the balance between a pure metal and a non metal or insulator. When used together, reflective roughness and metalness can produce a wide range of effects from unfinished stone to rubber to a perfect mirror. Transmission is the passage of light through a material. Physically based renderers model the way light is transmitted through a solid object.
Transparency controls how light is absorbed by the material. And refraction determines how light bends as it enters and leaves the object. Some physically based materials also simulate subsurface scattering. Translucent materials, such as wax, are accurately rendered by calculating how light is scattered within a solid volume. And those are the most common parameters of a physically based material.
- Choosing a visualization app
- Managing assets
- Shading with materials and textures
- Daylighting, practical lighting, and studio lighting
- Lightbox and macro photography
- Vehicles and large-scale objects
- Architecture and interior design
- Technical illustrations
- Rendering passes and light groups
- Rendering for print, prepress, and broadcast
- Animating turntables and orbits
- Rigging and animating a walkthrough