Distant trees - Sprites facing camera? Static? Or what?

Hello!
We're making an open world game. We had to dump SpeedTree due to various reasons, so our trees are just normal game objects with LOD.

The farthest LOD is a Sprite, which should be facing camera (a.k.a. billboard) . BUT when we do that, it needs to be Dynamic (non-static) so it can rotate towards camera with a script. But when it's dynamic, it cannot be loaded with Occlusion culling, which will be very bad with X thousand of trees around the world!

What should we do...? :C

 

I can't offer much help because I haven't done anything like this, but I think you want to look into using BillboardRenderers with BillboardAssets created by you at runtime instead of speedTree.

From the BillboardRenderer API doc: "BillboardRenderers that share the same BillboardAsset can be rendered in a batch if they are next to each other in the order of rendering"

Manual
https://docs.unity3d.com/Manual/class-BillboardRenderer.html

API
https://docs.unity3d.com/ScriptReference/BillboardRenderer.html
https://docs.unity3d.com/ScriptReference/BillboardAsset.html

 

Some older games that didn't bother with billboards used two perpendicular faces with the same texture.

Spoiler: Example

Depending on your needs it may or may not be a solution for you.