Troubleshooting light leaks in Adaptive Probe Volumes in URP

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

Light leaks often occur when geometry receives light from a Light ProbeLight probes store information about how light passes through space in your scene. A collection of light probes arranged within a given space can improve lighting on moving objects and static LOD scenery within that space. More info
See in Glossary that isn’t visible to the geometry, for example because the Light Probe is on the other side of a wall. Adaptive 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.
• Add an Adaptive Probe Volumes Options override to your scene.
• Enable Rendering Layers.
• Adjust Baking Set properties.
• Use a Probe Adjustment Volume.

Create thicker walls

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

Add an Adaptive Probe Volumes Options override to your scene

You can add a Volume, then add an Adaptive Probe Volumes Options override to the Volume. This adjusts the position that GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary use to sample the Light Probes.

1. Add a Volume to your sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
   See in Glossary and make sure its area overlaps the cameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
   See in Glossary position.
2. Select Add Override, then select Lighting > Adaptive 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 pixelThe smallest unit in a computer image. Pixel size depends on your screen resolution. Pixel lighting is calculated at every screen pixel. More info
   See in Glossary’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 Adaptive Probe Volumes Options settings.

Use Rendering Layer Masks

You can configure the Rendering Layer MasksA value defining which layers to include or exclude from an operation, such as rendering, collision or your own code. More info
See in Glossary in the Adaptive Probe Volumes panel in the Lighting window. This allow APV to assign a Rendering Layer Mask to each Light Probe.

For performance reasons, Adaptive Probe Volumes only supports up to 4 Rendering Layers Masks. You can use the list to create a new mask and use the dropdown to assign it any Rendering Layer. When lighting is generated, Unity will try to automatically assign a mask to each probe by looking at the Rendering Layer Masks of objects surrounding the probe. Additionally, you can use a Probe Adjustment Volume to override the Rendering Layer Mask assigned to Light Probes.

At runtime, renderers will only sample lighting data from probes that have a matching Rendering Layer Mask. If the object doesn’t match any of the Masks defined in the Lighting window, it will sample lighting from all the valid surrounding probes. Note that this feature requires Use Rendering Layers to be enabled in the URP Asset.

For example, in order to fix light leaking issues, you can create an Interior and an Exterior Rendering Layer Mask to ensure interior objects will never sample lighting data from exterior probes and fix light leaking through the walls. A renderer can have several Rendering Layers enabled in it’s Rendering Layer Masks. This is useful when dealing with dynamic objects that may want to sample lighting from both the exterior and interior probes.

You can visualize which layers are assigned to a probe: - Go to the Probe Volumes tab - Enable Display Probes - Set the Probe Shading Mode field to Rendering Layer Masks - Use the toggles in the Scene ViewAn interactive view into the world you are creating. You use the Scene View to select and position scenery, characters, cameras, lights, and all other types of Game Object. More info
See in Glossary Overlay to hide Probes matching a Rendering Layer Mask

Adjust Baking Set properties

If adding a Volume doesn’t work, use the Adaptive 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 Adaptive 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.

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

• Configure the size and density of Adaptive Probe Volumes
• Adaptive Probe Volumes panel reference
• Probe Volumes Options Override reference
• Probe Adjustment Volume component reference