Adding dirt to occluded areas

I'm sure you know by now how powerful baked lighting can be in Unreal Engine 4. It makes our scenes look ultra-realistic if done well, as the computed shadow maps don't have any equivalent in terms of quality if we use dynamic lighting. However useful they are, calculating lighting for our scenes isn't only helpful for this process of baking shadows—we can reuse this information in other ways within our materials. We have one useful node at our disposal that lets us tap into that data to drive the appearance of our materials. One common use for that is to apply dirt to areas that are occluded, which we'll look at here! Take a look at the following screenshot:

Getting ready

The scene that you can open if you want to follow along using the same assets is called 09_ 02_ PrecomputedAoMask_ Start and can be found in the Content Browser / UE4ShadersAndEffects / Maps / Chapter09 folder.

As always, you can use your own assets and levels, but there are some things you should...