Stationary Light

Moveable Light

Static lighting (baked lighting) basically shoots light rays and asks each mesh whether it is lit or in shadow. It will save the results into a texture (a light map). To call the texture is cheaper than calling dynamic lighting (which asks this question on every tick). Dynamic lighting is expensive.

Mobility Settings

Mobility settings work the same across all light types. Mobility asks “what does this light do, change, or how can it change while the game is running?”

• Static: Static lights are baked down. They cannot be altered at all during run time. Static lights are the best cost performance lights.
• Stationary: Default option for all lights. Stationary lights are a mix between static and moveable lights. Stationary lights bake all lighting information; whatever mesh face it directly hits can be altered during run time by the light (e.g., intensity, color, etc). But it cannot be moved or rotated (as that changes what faces it hits and, therefore, how it would bake).

Using a red light we can see the effect of a stationary light change at run time.The bounce light did not change (rebake) colors with the color change at run time.

Using a red light we can see the effect of a stationary light change at run time.

The bounce lighting did not change (rebake) with the change in light color at run time.

• Moveable: A moveable light can be fully altered during run time. It can be moved, rotated, details changing, on every frame. Moveable lights are the most expensive performance wise.

Light Mesh Agreement

The other aspect is that a mesh’s mobility settings should align with the lights that you want to affect that mesh. It is like an agreement between the mesh and light. Light A says “I cast light to Mesh A” and mesh A says “I receive light from Light A.”

Object Sampling

Volume Lighting Samples allows you to visualize the light samples from various points. The light samples will impact all three types of meshes (static, stationary and movable). You can find the options in the viewport “Show” menu. Samples will only generate inside a lightmass importance volume and along the flat walls/floors.

A screenshot of the lighting samples (the grey boxes).