ParticipatingMedium

Marks its entity as a volume of fog, smoke, dust or steam — something light has to travel through. What is behind the volume comes out dimmer than what is beside it, and overlapping volumes stack.

local id = entity.spawn("fog_bank").id
entity(id).component.add("ParticipatingMedium", {
    sizeX = 30, sizeY = 8, sizeZ = 30,
    density = 0.15,
})

Fields

Field	Meaning
shape	"box" (default) or "sphere"
density	Extinction per world unit. 0 releases the medium.
sizeX / sizeY / sizeZ	Half-extents, for a box
radius	Radius, for a sphere

density is the physical knob: a ray crossing d world units of a medium of density k leaves with exp(-k * d) of the light it entered with. A 20-unit bank at 0.15 therefore passes about 5% of the light straight through it.

The entity's position places the volume; move the entity and the shadow moves with it.

Notes

• The light-space map is sized to the bounding sphere of everything registered. A small bank sharing a scene with a very large one lands on few texels — set extent and centre through mediaTransmittance.set to bias the map toward the region you care about.
• Attenuation applies to surfaces. The sky keeps its own colour.
• The attenuated light is the sun's: sunDirection sets which way the map's rays travel.

See mediaTransmittance for the scene-wide settings and the direct API.