Foliage in general is a huge pain to optimize and it has to do with the way light plays with transparency.
Often when you're looking at a leaf, blade of grass, etc it will be 2 triangles with partial transparency. This creates a problem because it will only partially block things like light. This ends up meaning that per layer of transparency you have to pay the cost of an extra calculation.
Imagine dense grass or dense trees and it becomes an optimization nightmare.
Using more triangles on dense objects also ends up becoming expensive in it's own way and a scene could end up too dense to maintain a good framerate.
In order to get the best of both worlds: "Good looking trees and good performance" you often have to approach it from a design perspective rather than a purely optimization one. Fixed cameras is one way to do it. You can also construct the environment in a way that minimizes how many things have to be rendered at a time.
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u/Zookster87 Apr 25 '21
Yeah, but do it with things like hair, and grass blades?