The purpose of this workflow is to generate a lighting system that will produce good indirect illumination without the use of Final Gather. The point is to be able to animate objects and get a good updated lighting solution for each frame. We will be using AO with the Custom Ambient Light Color map. The map will be a spherical projection of a mr Physical Sky that will align with the scene's Sun light direction. We will use this utility to mass update our A&D material.
The combination of the map and AO gives the scene the illusion of daylight indirect illumination that takes into calculation the proximity between objects (Fig.01).
Materials, Gamma and Exposure
This workflow uses the AO map option in the A&D material, so it is crucial that all your materials are A&D (no Pro Mat stuff). Now, just try to follow Fig.02 – 03 to start with and change it later as you see fit. The Unitless Physical scale use is important in this workflow; it will work accurately with the image brightness and will look normal in the Material Editor, so you don't get over-exposed material previews, which makes it hard to work with.
Create a few objects on a plane so you can test shadows, AO and lighting. Make the objects life sized so you can see how they will work with a real world scale. If your objects are too small or too big you'll get extreme results (too much or not enough shadows and light). The large sphere in my scene is 12' in diameter; you can see the RPC on the side for scale. Now add a daylight system and make sure you create a mr Physical Sky shader in your environment. You can make a test render now and save it for a later comparison.
Now we will replace the Skylight and FG solution with our AO Ambient Light map. We do that by the use of a bitmap in the Custom Ambient Light Color. The bit map in this example was generated using a WrapAround (Lume) shader in the Lens slot (Render Settings > Renderer) in an empty scene with Daylight system and a mr Physical Sky in the environment map. The camera was pointing at the straight horizon. After some blurring in Photoshop, it should look like this (Fig.04).