Similar to Baked Indirect Lighting Mode, Shadowmask Lighting Mode combines real-time direct lighting with baked indirect lighting. However, Shadowmask Lighting Mode differs from Baked Indirect Lighting Mode in the way that it renders shadows. Shadowmask Lighting Mode allows Unity to combine baked and real-time shadows at runtime, and to render shadows in the far distance. It does this by using an additional lightmap Texture known as a shadow mask, and by storing additional information in Light Probes.
Shadowmask Lighting Mode provides the highest fidelity shadows among all the Lighting Modes, but has the highest performance cost and memory requirements. It is suitable for rendering realistic scenes where distant GameObjects are visible, such as open worlds, on high-end or mid-range hardware.
Shadowmask Lighting Mode has these quality settings:
When you set a Scene’s Lighting Mode to Shadowmask and your Project uses the Distance Shadowmask quality setting, Mixed Lights behave as follows.
When you set a Scene’s Lighting Mode to Shadowmask and your Project uses the Shadowmask quality setting, Mixed Lights behave as follows.
In the Built-in Render Pipeline:
Follow the instructions in the HDRP Shadowmask Lighting Mode documentation.
You can use the Shadow Distance property to limit the distance up to which Unity draws real-time shadows.
At runtime, Unity uses the shadow mask to determine whether a pixel is in shadow or not. The shadow mask Texture contains occlusion information about baked lights. It shares the same UV layout and resolution with its corresponding lightmap. It contains occlusion information for up to four lights per texel, stored in RGBA format.
If more than four lights overlap, any additional lights fall back to Baked Lighting. The baking system determines which lights fall back to Baked Lighting, and this stays consistent across bakes, unless you modify one of the overlapping lights. Light Probes also receive the same information for up to four lights.
Unity computes light overlapping independently of shadow receiving objects. So, an object can get the influence of ten different mixed lights all from the same Shadowmask/Probe channel, as long as those light bounding volumes don’t overlap at any point in space. If some lights overlap then Unity uses more channels. And, if a light does overlap while all four channels are already in use, that light falls back to fully baked.