Chapter 7: Mixed lights render as baked
Figure 15. A simple scene containing nine mixed lights baked in Shadowmask mode. Notice that some spheres are unlit and appear as dark (left). Light Overlap debug view highlights overlapping lights in red (center). As shown in the Shadowmask debug view, lightmapper discards overlapping lights, and does not include them in the shadow mask texture (right).
7.1 Why does this happen?
When using Shadowmask lighting mode, only four mixed lights can overlap. Lights exceeding this limit will become baked lights.
In Subtractive lighting mode, all lights – except for directional lights – will not cast realtime shadows. This is an inherent limitation of this lighting mode.
7.2 How to fix it?
7.2.1 Change light placement and radius
To verify that light overlap is the issue, switch to Light Overlap scene view draw mode after generating lighting. This scene view draw mode will highlight overlapping lights in red.
Move the affected lights so that they no longer overlap. Otherwise, adjust the Range or Spot Angle parameters in the Light component. Generate lighting again after making the changes.
7.2.2 Switch to a different lighting mode
Each lighting mode comes with its own advantages and limitations. If your project will be lit using a single directional light, then Subtractive lighting mode might be a better choice than Shadowmask. Please consult the Unity manual page on lighting modes to make the best decision for your project.