Mesh performance impact

Hello. Created a few rocks for a project and build a medium-size part of a mountain with it, looks good but after merge i realized that it has 150k triangles and 80k vertices. How bad it will hit performance?

You merged them? In your 3D modelling program?
(also 150k is not ideal but sill fine if you don’t plan on deploying it extremely often, but I’m more concerned about the mesh itself you created)

No, i merged them in unreal. Should i decrease the amount of triangles? Probably i can reduce it to 15-30k, i just don’t really know where to find specific numbers for optimization in unreal.

If you use assets with many polygons sparingly, it’s fine. As a reference, the dummy player model already has around 41k tris, besides, if you let the engine generate LOD, it will take the edge off even more. Large dynamic shadows, complicated shaders and many big textures have much more of an impact on performance.
It all depends on how much you are in need of optimizing it. If you want to go for distributing your product on mobile devices, then yes, the effort might be worth it, but otherwise I’d say poly count is not the primary concern as long as you’re not subdividing the hell out of a mesh.
If you’d have a small flower with 150k tris that’d be worse, part of a mountain is still well within reason.

Thank you, i will try to reconsider whole picture for optimization purposes then.