Not saying this is the correct thing to do but when i tackled this issue in my game I was using very realistic forest assets and need to increase performance massively. Some of the steps/tricks I took were:
- Use HISM (not ISM, as HISM can cull) this is the same process as the foliage tool and procedural generation.
- Set a cull value on the assets (especially for procedural) so that only things in a certain radius around the player actually render.
- I used fog to help hide the new meshes ‘popping in’.
- I used nanite.
- I found that using lumen caused an enormous amount of the performance issues alongside nanite. I switched to screen space.
- I removed any unnecessary collisions from the assets and replaced the necessary ones with simple columns.
Hope some of this helps 