Quick answer: Unreal Niagara mesh particles not tessellating despite material supporting it? Tessellation requires opt-in on the mesh renderer; defaults to off.
Procedural water particles with tessellation material; particles render flat.
Enable on mesh renderer
Mesh Renderer > Tessellation = Enabled. Particles tessellate.
Or accept flat
Tessellation is expensive; flat may be fine. Decision per-project.
Audit material vs renderer
Material supports != renderer uses. Both must agree.
“Tessellation is opt-in at multiple layers. All must agree.”
If you author tessellation materials for VFX, the renderer config is the bridge. Document.