How it works...

Remember how we were talking about each renderer having its own implementation of a PBR workflow? Well, we have just taken a look at how Epic has chosen to set up theirs!

As we have already said, efficiency and speed are at the heart of any real-time application. These are two factors that have heavily influenced the path that the engineers at Epic have chosen when coding their physical approach at rendering. That being the case, the parameters that we have tweaked are the most important ones when it comes to how Unreal deals with the interaction between light and 3D models. The base color gives us the overall appearance of the material, whilst roughness indicates how sharp or blurry the reflections are. Metallic enables us to specify whether an object is made out of metal, and the specular node lets us influence how intense those reflections are. Finally, using normal maps allows for the modification of the direction in which the light gets reflected—a useful technique for adding details without actually using more polygons.

The previous parameters are quite common in real-time renderers, but not every program uses the same ones. For instance, offline suites such as VRay use other types of calculations to generate the final output—physically based in their nature, but using other techniques. This shows us that, at the end of the day, the PBR workflow that Epic uses is specific to the engine and we need to be aware of its possibilities and the limitations.

Throughout the current recipe, we have managed to take a look at some of the most important nodes that affect how the physically based rendering gets tackled in Unreal Engine 4. Base color, roughness, specularity, ambient occlusion, normal maps, and the metallic attribute all constitute the basics of the PBR workflow.

Having seen all of them, we are now ready to start looking into how to build more complex materials and effects. And even though we still need to understand some of the other areas that affect our pipeline, we can do so with the certainty that the basics are covered.