Intermediate Tutorial


Physically Based Rendering (PBR)


45 minutes

Posted on: June 20, 2019

Learn Sumerian
Physically Based Rendering (PBR)

Tags

materials
lighting
PBR
HDRI
physically based rendering
environment lighting,

In this tutorial you will learn about:

PBR Material Setup from third-party asset

In this tutorial, we look at physically based rendering (PBR) and environment lighting and how they’re used in Amazon Sumerian. You’ll learn how to set up a simple PBR material using both the Metalness and Specular PBR materials in Sumerian, based on assets from a third-party content site. You can use these same principles to set up your own content.

Prerequisites

Before you begin, you should have completed the following tasks and tutorials:

What Is PBR?

Physically based rendering (PBR) is the method of shading and rendering that more accurately represents how light interacts with surfaces. This is different from the classic shader and dynamic lights in Sumerian, which use older lighting algorithms that don’t take into account things like energy conservation and microsurface interactions. This means that when you use the PBR lighting and shading methods, metal and dielectric (nonmetal) objects render closer to their real-word counterparts.

We have two PBR shading materials in Sumerian: Metalness (PBR metal/roughness) and Specular (PBR specular/glossy). These two materials use different equations for calculating how the specular reflections are displayed on the materials but they also share several of the same properties.

In choosing which material (Metalness or Specular PBR material) to use, keep the following in mind:

  • The Specular material gives you more control over the reflectivity of nonmetal materials. This provides a full-color input for reflective (specular) color. Artists with a lot of experience in traditional shaders might prefer the Specular material, because Specular is more similar in the maps and methods used in those types of shaders.

  • The Metalness material simplifies the difference between metal and non-metal (dielectric) objects. This can make it easier to author content. However, the material transitions (places where the material changes from metal to dielectric) can sometimes leave a white line artifact. For this reason, it’s best to use different materials for your metal and dielectric objects.

  • The Metalness material uses Base Color (the color of the object before specular reflections are calculated), Metalness (how and where the material is metal), Roughness (the shape of the specular reflection), and Specular F0 (to modify the reflectivity of nonmetal objects).

One of the major benefits of PBR is that any object that is set up with a PBR material should work under many different lighting conditions. This means that you don’t have to update the materials for all of your objects in a scene just because the lighting setup changed to achieve the best look. It should give your assets a consistent high-quality appearance.

Environment Lighting and HDRIs

A high dynamic range image (HDRI) is an image used to reproduce a greater dynamic range of luminosity. This uses the image format .hdr. When using an HDRI, the scene is lit with luminosity information from an image, instead of, or in combination with, the existing dynamic lights in Sumerian. The reflections are also based on the HDRI, making the scene more physically accurate.

Where Do I Find the Assets for Use with PBR?

There are many third-party sites that offer 3D assets that may or may not be set up with PBR materials. However, content on these sites isn’t strictly regulated. This means that sometimes the authors of the 3D content don’t provide every texture needed for the PBR setup. If you’re seeking PBR-compatible assets, look into the descriptions and see if the assets are set up with a PBR material, and which PBR material they use (Metalness or Specular).

Additionally, although PBR is a standard material, there are several variations of the Metalness or Specular shaders for use within different rendering engines. This means that although you might have an asset that is set up for the Specular material in one rendering engine, it might not have exactly the same setup as the Specular material in Sumerian. Some of the textures needed for Sumerian PBR materials may need modification, if the third-party asset doesn’t have the same PBR setup.

Look at the images in this tutorial for each texture type, and try to gauge which textures provided with your third-party asset will work best. We recommend the following sites:

Step 1: Select the PBR Material

To set up the PBR material, select the material for your asset and then change the Shader attribute from Classic to PBR.

  1. Create a scene using the Empty Scene template.

  2. Toggle off the grid.

  3. Import the asset you’ll work with, including its textures. You can choose to import all the files at the same time. Alternatively, you can drag and drop all the assets onto the canvas. We’ll use a Robot Arm asset.

  4. Select the material for your imported assets through the Assets panel or Entities panel.

  5. In the Inspector panel on the right, you can see the Material component property settings. On the Shader property menu, choose PBR.

    The Material component displays the two PBR materials: Metalness and Specular.

  6. Choose Metalness.