Hello everyone!
Today I'd like to talk about light expression in 3DCG. Specifically, beam lights that you often see in live performances. The point is that simply placing lights in your 3D scene is insufficient to create realistic beam effects.
Beam Light Expression in Unity
Let's discuss this using Unity. There are various assets available for expressing beam lights in Unity, but today we'll try using Volumetric Fog in HDRP (High Definition Render Pipeline).
This is what our stage looks like. Let's place spotlights here. We'll position them to shine down diagonally from the upper left and right.
Here's how it looks with spotlights placed and lighting set up. This is a common sight. You might think, "I've placed the lights, so I'm done, right?" But that's not the case.
Areas outside the direct light beams are completely dark.
In real-world lighting phenomena, areas don't become completely dark. When light hits a surface, it reflects and affects the surrounding environment as well.
Being Conscious of Diffuse Reflection
Let's look at a photograph from a real live performance. Even though the lights are pointing at the ground, the ceiling is illuminated.
This happens because light that hits the ground creates Diffuse reflection, brightening the ceiling and surrounding walls.
https://en.wikipedia.org/wiki/Diffuse_reflection
With this diffuse reflection in mind, let's adjust our lighting.
Now details in areas that were previously completely black are visible. The difference becomes clear when comparing the two.
Areas that were lost in darkness can now be seen, creating a stronger sense of light presence. Incorporating these expressions dramatically improves realism. In reality, brightness varies depending on the reflective properties of materials, so keep this in mind as well.
Summary
In CG, placing lights doesn't necessarily guarantee natural light expression. While rendering calculations can express light reflection, in real-time scenarios, you need to control and create these expressions yourself.
By closely observing real light and understanding the phenomena that occur, you can improve the quality of your scenes significantly, so please give it a try!
↑ This is a scene where I'm testing these concepts to create a good atmosphere. It still needs adjustment, but I'll introduce it once it comes together nicely.