filibis,
IRVs (Irradiance Volumes) can be one of the most frustrating issues in Eevee to get GI lighting correct in an interior scene. After working on many interiors. I usually don’t have to many issue with IRVs now. See my workflow below.
Tips for Main and Nested IRV’s are:
- Create a main IRV for the room that is not to dense no more 4x4x4 or less. The goal of the main IRV is to have just basic GI coverage on the room.
- Having too dense of a main IRV usually creates more problems by having probes intersecting objects and creating GI artifacts. Dense IRV also increase the baking time considerably.
- Stretch the main IRV close to walls.
- If certain areas of the room having missing GI lighting is okay, because it will covered later with nested IRVs.
- Distance for the main IRV should be 1.0.
- Distance for nested IRV typically range between 0.3 to 0.6. In this scene I have a nested IRV on the wall with distance of 0.5.
- Falloff for the main and nested IRV leave it at the default of 1.0.
- The Intensity I do vary depending on the scene lighting between 0.6 to 1.2.
- To achieve good blending between the main IRV and the nested IRV. Make sure the size of the nested IRV has some slight overlap with the main IRV probes. Also that the intensity are the same. See image below.
Wireframe of Main IRV (4x4x3) in yellow and the nested IRV (2x1) in red. Notice the size of the distance in the nested IRV.
In this scene I added the Nested IRV because the Main IRV created a dark lighting GI artifact on the wall by the picture frame. See render without the nested IRV below.
Now the render using both the Main IRV and Nested IRV (2x1). See how smooth the blending is on the wall between the Main IRV and Nested IRV and correcting the previous dark GI lighting artifact.
The scene lighting consist of an area light and sun Light:
The lights in this scene are quiet basic one area just outside the window. The area light creates a good fill light on the room. One sun light creating nice back lighting and highlights on the plants and light on the chair. This increases the visual interest and dynamics on the interior scene. I usually don’t add area lights inside an interior.