Radii, edges, and shadows

The Geometry tab on a light has a stack of related controls that decide how a light fades from its bright core to nothing — and how walls and tokens carve shadows out of it. This page walks through each one and what to reach for when.

Bright and dim radii

The Bright radius and Dim radius fields below the main radius give you a Foundry-style three-zone falloff:

• Inside the bright radius — full intensity (a flat plateau).
• Between bright and dim — smooth fade from full to half intensity.
• Between dim and outer radius — fade from half to zero.

Use it for a torch with a narrow bright core and a long fall-off, or a streetlamp with a hot centre.

When Bright radius equals Outer radius (the default), there’s no plateau and the light uses the simpler edge-softness curve below.

Edge softness

The Edge softness slider (0..1) controls how the light’s outer rim fades:

• 0 — hard cut-off at the outer radius (a paper-cut disc).
• 1 — full radial fade from centre to edge (the default soft glow).
• intermediate values — bright plateau in the inner part, soft fade in the outer band.

This same slider also controls how soft the fog of war reveal is, when the light has Reveals fog of war turned on (see Fog of war — light-driven reveal).

Tip

Edge softness and bright/dim radii stack — the bright/dim plateau is applied first, then edge softness fades the outer rim further. For a Foundry-style “bright zone with a hard cut” use bright radius < outer radius and edge softness 0. For “smooth glow with no plateau” leave bright/dim alone and use edge softness 1.

Source size (soft shadow penumbras)

When walls block your light, the shadow edge is normally a sharp line. The Source size slider gives a physically-plausible soft shadow:

• 0 — point-source. Sharp shadow lines (the v2 default).
• 0.5 — moderate penumbra fringe at the wall edge.
• 1 — wide source. Blurry, diffuse shadows.

Visualise it like this: a candle (small source) casts crisp shadows; a window (large source) casts soft ones.

Caution

Source size only changes shadows where walls clip the light. If your scene has no walls, the slider has no visible effect — use Edge softness above for the outer rim of the lit disc.

Occlusion roughness

The Occlusion roughness slider scatters wall-edge samples by a small amount so shadow lines aren’t perfectly straight. Cheaper than source size and complementary — use both for a textured, “hand-painted” feel.

• 0 — perfectly straight wall shadows (default).
• 0.5 — noticeable jitter on the edges.
• 1 — heavily scattered.

Self-exclude

The Self-exclude slider (0..1) masks out a centre disc on the light. Useful for:

• Token-mounted lights so the carrier (the torch-bearer) isn’t washed out by their own torch.
• Donut / ring effects for stylised magical lights.

0 = no mask (default). Higher values cut a bigger hole.

Cast shadows on tokens

The Cast shadows on tokens switch makes the light treat tokens as solid occluders — every token within the light’s reach (except the one carrying the light, if any) blocks light just like a wall.

This is off by default because it adds rendering work per light. Turn it on for dramatic moments — a creature silhouetted against a fire — rather than for every light in the scene.

Putting it together

A few common recipes:

You want	Try
Realistic candlelight in a tight room	Bright 30, Dim 100, Outer 200, Source size 0.3
Hard-edged spell circle (no soft glow)	Edge softness 0, Source size 0
Soft sunbeam through a window	Outer 600, Edge softness 1, Source size 0.6 (with walls forming the window)
Hooded lantern (carrier silhouetted)	Self-exclude 0.15, Cast shadows on tokens on, attach to token

Related

• Lights — basics — placing and shaping a light.
• Fog of war — light-driven reveal — how the Reveals fog of war toggle uses the same edge softness.
• Token vision — basics — the same softness control applies to a token’s vision sphere.