Relationship between Virtual Shadow Map and Contact Shadow

[wren945g]

How do I make a specific actor ONLY use Contact Shadow while other actors use Virtual Shadow Map?

I’m asking this because this video says that, in Fortnite, grass only casts screen space contact shadow as an optimization for Virtual Shadow Map.

Battle-Testing UE5 Next-Gen Systems with Fortnite | GDC 2023

The document of Virtual Shadow Map also mentions using contact shadow for foliage:

Virtual Shadow Maps In Unreal Engine | Unreal Engine 5.4 Documentation |...

How do I prevent grass from using Virtual Shadow Map? I thought Virtual Shadow Map was a project-wise setting.

I’m really confused with these terms. So normally Virtual Shadow Map and Contact Shadow work together? Shadow Map is like the real big shadow, and Contact Shadow is like the shadow at the contact area, sort of a heavier version of ambient occlusion?

Thanks.

[wren945g]

Well I’ve figured it out. Since virtual shadow map is the default shadow map, to turn it off, just turn off cast dynamic shadows on actors that you want to substitute contact shadow. then turn on its contact shadow.