Emissive Boost
Where: select a mesh component, then search Emissive Boost in its Lightmass Settings. This page describes the per-component control, not a similarly named parameter you may have created inside a material.
Emissive Boost multiplies the light a material emits into Spectral's bake. It does not multiply the visible Emissive Color of that material during gameplay. This lets a luminous panel cast more or less baked light without making the panel itself look brighter or dimmer.
Values
| Value | Baked emission |
|---|---|
| 0 | No emission from this component in the bake. The visible material can still glow. |
| 0.5 | Half the material's emission strength. |
| 1 | Unmodified emission. Start here. |
| 2 | Twice the emission strength. |
The multiplier applies to all materials on that component. It cannot brighten one material slot and leave another unchanged. For that, adjust the material setup or split the geometry into separate components. Multiplying black emission still gives black: boost does not make a non-emissive material emit.
How it fits Spectral
Spectral explicitly applies this value in its bake material shader, including when gathering emission for probes. It changes the recorded light source, rather than applying a brightness filter to the final image. Other lights, exposure, and material response still affect the final appearance, so doubling the boost does not mean every pixel on screen becomes twice as bright.
The resulting probe lighting can also illuminate probe-lit fog. The fog's own lighting multipliers remain separate controls.
Example: a glowing wall sign
Set the sign's material emission to get the appearance you want. If its baked spill on the wall is too strong, reduce the sign component's Emissive Boost and rebake. If you want only the visible glow, use 0. If you want more spill without changing the sign's visible surface, raise the boost gradually.
A very high boost on a tiny emitter can make sampling artifacts more obvious. Check the emitting area and bake quality before using a large multiplier to brighten an entire room.
When to rebake
Every change to Emissive Boost needs a new bake for affected lightmaps and probes. Existing baked spill will not disappear just because you set the value to 0. This setting is unrelated to Spectral Subsurface Boost, which adjusts transmitted light through supported subsurface materials rather than emission.