PBR workflow in Thea

Materials

In this article we will learn how to work with PBR textures from sites such as:
Substance Source, Poliigon, Quixel, etc.

For a better understanding of the Physically-Based Rendering (PBR) methodology, we recommend having a look at the PBR Guide by Allegorithmic.

The PBR workflow

Thea Render uses the Metal/Roughness workflow and expects specific maps like color (also called albedo and diffuse), metallic and roughness.

PBR textures

Albedo / Diffuse map
The Albedo map defines the base color of the material with the lighting (highlights & shadows) removed.

Ambient Occlusion map
The Ambient Occlusion map can be used to make the details and shadows of a material more pronounced. The Ambient Occlusion map should be blended with the diffuse channel in multiply (*) mode.

Roughness map
The roughness map defines the sharpness of the reflections and should be added to the roughness channel. If you have a glossiness map instead of roughness then all you have to do is to apply the glossiness map to the roughness channel and invert it.

Normal map
The normal map in Thea Render needs to be in OpenGL format otherwise the material will appear inverted. The following list provides the type of the normal map that these sites provide.

 

CreatorNormal type
Poliigon, Quixel Megascans, Texture Haven, CC0 Textures, 3D TexturesOpenGL
Substance Source, CG BookcaseDirectX

 

If you know that the type of the provided normal map is DirectX then to convert it to OpenGL all you have to do is to invert the green channel. Here is how to do this in several image editing applications:

  • Photoshop: Switch to the Channels tab, click on the Green Channel and then hit Control+I on the keyboard to invert the channel. Click on the RGB Channel to go back.
  • Krita: Press Control+M to open the Color Adjustment Curves panel. Click on the Channel drop-down and select Green from the list. Grab the left point and move to the top of the graph. Grab the right point and move it to the bottom of the graph. Hit OK.
  • GIMP: Open the Curves panel (Colors > Curves…). Select Green from the Channels drop-down list. Grab the left point and move to the top of the graph. Grab the right point and move it to the bottom of the graph. Hit OK.

Tip
When a normal map has been assigned to the bump channel, you also need to enable the normal map option so that Thea treats it as one.

Metallic Map
The metallic map is used as a layer weight of the basic layer controlling how much of the metal layer below it is visible.

Bitmap-Based preset in Thea for SketchUp

The bitmap-based preset is the latest addition in the available presets in Thea for SketchUp. This automates the process of creating Thea materials from PBR textures.