Virtual Emitters

intermediate tasks

Radiant GI (URP) · Common Tasks

Virtual Emitters

Virtual Emitters are invisible GI light sources that can be placed anywhere in the scene. They inject indirect lighting into the GI computation, making it possible to simulate off-screen or hidden light sources that would otherwise be missed by the screen-space ray tracing.

Enable first: Virtual Emitters must be enabled in the Radiant GI volume override before they take effect.

Adding a Virtual Emitter

There are two ways to add a virtual emitter to your scene:

  1. Menu: Go to GameObject > Create Other > Radiant GI > Virtual Emitter.
  2. Script: Add the RadiantVirtualEmitter component to any GameObject or character.

GI Color

PropertyDescription
ColorHDR emission color of the virtual emitter.
Add Material EmissionAdds the emission color of a material to the GI color, so the emitter follows the material's emissive intensity.
Target RendererRenderer to read the emission color from. Defaults to a renderer found on this GameObject.
MaterialOptional explicit material to read the emission from. Useful when the renderer uses several materials.
Material IndexIndex of the material in the renderer when no explicit material is assigned.
Emission Property NameShader property to sample for the emission color (default _EmissionColor).
IntensityEmission intensity multiplier applied on top of the GI color.

Shape

Each emitter can be a Point or a Box. Box emitters fill a volume with light, while Point emitters emit from a single position. Box emitters honor the GameObject's transform rotation, so you can tilt or align the box with walls and ceilings.

PropertyDescription
ShapePoint emits from the GameObject position. Box emits from a rotated box centered on the GameObject. Use Box for ceiling lights, fluorescent strips, neon signs, or window light shafts.
Shape SizeWorld-space size of the box (only used when Shape is Box). The box rotates with the transform.
RangeFalloff distance from the emitter. For Point emitters, distance from the position. For Box emitters, distance from the closest point on the box surface, producing a volumetric falloff around the shape.

Area of Influence

The area of influence is a separate AABB used to clip indirect light, preventing it from leaking through walls or into adjacent rooms. It is independent of the emission Shape.

PropertyDescription
Box Center / Box SizeDefines the AABB that clips the emitter contribution.
Bounds In Local SpaceWhen enabled, Box Center is interpreted relative to the GameObject's position so the volume follows the emitter as it moves.
Fade DistanceSoft fade applied near the area-of-influence edges. 0 = hard cutoff.

Rendering Layers

Each emitter exposes a Rendering Layer Mask that restricts which surfaces receive its light. This is useful for isolating lighting on characters, props, or specific rooms.

Requires opt-in: Per-emitter rendering layers only apply when the Use Rendering Layers option is enabled on the Radiant Render Feature in your URP Renderer asset, and the active URP Pipeline asset has rendering layers enabled. When disabled, all emitters affect all surfaces (legacy behaviour).

Limits

There is no limit to the number of virtual emitters in a scene, but only the 32 closest emitters to the camera will be active at any given time.

Tip: Virtual emitters are great for placing colored light behind doors, around corners, or under furniture — areas where the camera can't see the actual light source but where indirect illumination should still be present. Use Box shape with rotation for ceiling panels and window light shafts.
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