Fix issues with Probe Volumes

Adjust settings or use Volume overrides to fix artefacts from Probe Volumes.

How Light Probe validity works

Light Probes inside geometry are called invalid probes. The Universal Render Pipeline (URP) marks a Light Probe as invalid when the probe fires sampling rays to capture surrounding light data, but the rays hit the unlit backfaces inside geometry.

URP uses the following techniques to minimise incorrect lighting data from Light Probes:

  • Virtual Offset tries to make invalid Light Probes valid, by moving their capture points so they're outside any colliders.
  • Dilation detects Light Probes that remain invalid after Virtual Offset, and gives them data from valid Light Probes nearby.

You can check which Light Probes are invalid using the Rendering Debugger


In the Scene on the left, Virtual Offset isn't active and dark bands are visible. In the Scene on the right, Virtual Offset is active.


In the Scene on the left, Dilation isn't active and some areas are too dark. In the Scene on the right, Dilation is active.

Fix dark blotches or streaks

Adjust Virtual Offset

You can configure Virtual Offset Settings in the Probe Volumes panel in the Lighting window. This changes how URP calculates the validity of Light Probes.

You can adjust the following:

  • The length of the sampling ray Unity uses to find a valid capture point.
  • How far Unity moves a Light Probe's capture position to avoid geometry.
  • How far Unity moves the start point of rays.
  • How many times a probe's sampling ray hits colliders before Unity considers the probe invalid.

You can also disable Virtual Offset for a Baking Set. Virtual Offset only affects baking time, so disabling Virtual Offset doesn't affect runtime performance.

Adjust Dilation

You can configure Probe Dilation Settings in the Probe Volumes panel in the Lighting window). This changes how URP calculates the validity of Light Probes, and how invalid Light Probes use lighting data from nearby valid Light Probes.

You can adjust the following:

  • The percentage of backfaces a Light Probe can sample before URP considers that probe invalid.
  • How far away from the invalid probe Unity searches for valid probes to contribute lighting data.
  • How many iterations of Dilation URP does during the bake.
  • How to weight the data from valid probes based on their spatial relationship with the invalid probe.

How you adjust Light Probe density affects the final results, because URP uses the settings as a multiplier to calculate the distance between probes.

You can also disable Dilation for a Baking Set. Dilation only affects baking time, so disabling Dilation doesn't affect runtime performance.

Fix light leaks

Light leaks are areas that are too light or dark, often in the corners of a wall or ceiling.


A light leak.

Light leaks often occur when geometry receives light from a Light Probe that isn't visible to the geometry, for example because the Light Probe is on the other side of a wall. Probe Volumes use regular grids of Light Probes, so Light Probes might not follow walls or be at the boundary between different lighting areas.

To fix light leaks, you can do the following:

Create thicker walls

Adjust walls so their width is closer to the distance between probes in the local brick

Add a Volume to your scene

You can add a Volume, then add a Probe Volumes Options override to the Volume. This adjusts the position that GameObjects use to sample the Light Probes.

  1. Add a Volume to your scene and make sure its area overlaps the camera position.
  2. Select Add Override, then select Lighting > Probe Volumes Options.
  3. Enable Normal Bias, then adjust the value to move the position that GameObject pixels use to sample the Light Probes, along the pixel's surface normal.
  4. Enable View Bias, then adjust the value to move the position that GameObject pixels use to sample the Light Probes, towards the camera.
  5. Disable and enable Leak Reduction Mode to check if it improves light leaks.

Volumes only affect the scene if the camera is near or inside the volume. Refer to Understand volumes for more information.

Refer to Probe Volumes Options Override reference for more information on Probe Volumes Options settings.

Adjust Baking Set properties

If adding a Volume doesn't work, use the Probe Volumes panel in the Lighting window to adjust Virtual Offset and Dilation settings.

  1. In Probe Dilation Settings, reduce Search Radius. This can help in situations where invalid Light Probes are receiving lighting data from more distant Light Probes. However, a lower Search Radius might cause light leaks.
  2. In Virtual Offset Settings, reduce Search Distance Multiplier and Ray Origin Bias.
  3. If there are light leaks in multiple locations, adjust Min Probe Spacing and Max Probe Spacing to increase the density of Light Probes.
  4. Select Generate Lighting to rebake the scene using the new settings.

Note: Don't use very low values for the settings, or Dilation and Virtual Offset might not work.

Add a Probe Adjustment Volume component

Use a Probe Adjustment Volume component to make Light Probes invalid in a small area. This triggers Dilation during baking, and improves the results of Leak Reduction Mode at runtime.

  1. In the Probe Volume Inspector, select Add Component, then select Light > Probe Adjustment Volume.
  2. Set the Size so the Probe Adjustment Volume area overlaps the Light Probes causing light leaks.
  3. Set Probe Volume Overrides > Mode to Invalidate Probes, to invalidate the Light Probes in the Volume.
  4. If you have a Volume with a Probe Volumes Options override, enable Leak Reduction Mode.
  5. In Probe Volume Settings, select Generate Lighting to rebake the scene using the new settings.

Using a Probe Adjustment Volume component solves most light leak issues, but often not all.

If you use many Probe Adjustment Volumes in a scene, your bake will be slower, and your scene might be harder to understand and maintain.

Refer to Probe Adjustment Volume component reference for more information.

Fix seams

Seams are artefacts that appear when one lighting condition transitions immediately into another. Seams are caused when two adjacent bricks have different Light Probe densities. Refer to bricks for more information.


Two seams.

To fix seams, do the following:

  1. Add a Volume to your scene and make sure its area overlaps the position of the camera.
  2. Select Add Override, then select Lighting > Probe Volumes Options.
  3. Enable Sampling Noise, then try adjusting the value to add noise and make the transition more diffuse. Noise can help break up noticeable edges in indirect lighting at brick boundaries.

Additional resources