Working on my last render I found an interesting idea when iterating my scene’s lighting. I haven’t seen it elsewhere, but it’s possible it has been done before.
Usually, one wants to iterate over one scene uniformly (modeling, lighting, etc) to catch early problems in composition, idea, etc. However, sometimes it is hard to pre visualize how lighting is affecting an unfinished scene, as it is essentially a vector field and maybe you don’t have enough geometry.
So the main idea is adding spheres on some specific places you want to see how light is affecting the scene. Having placeholder geometry is definitely not a new idea (and essential when building a scene), but forcing these objects to be spheres helps a lot to visualize the light field at that point in space in particular.
Let’s do an example with a piece I’m working on. My reference is the following painting by John Howe:
So after a few placeholder objects and making sure the camera is correctly aligned, I can start working on very early lighting:
However, in the reference there’s a lot of light leaking from this door, either by indirect lighting or just artistic license. But I haven’t even started to work on the dragons and decorations! So one thing I can do is just add spheres:
Now it is very clear how my scene is going to react to lighting even before I have highly detailed geometry! In fact, doing this I ended up adding a few fake indirect lights for the lintel, which intersect with the top spheres (that’s fine, there won’t be geometry there that big). This is because I could now visualize how light was lacking in those places.
The spheres can be big or small, they can have different materials (they should imitate the materials that will be contained there), etc. And they should all be in a separate layer or group so it’s easy to exclude from render.
So the idea is very simple and very effective I think. It is similar to any game engine’s reflection probes, as they share some of the principles behind them.