best way to render a galaxy-ful of particles?

I'd like to do a galaxy simulation containing thousands (or better yet, millions) of stars swirling around as stars do. This is going to run on Quest (2), so maintaining a high frame rate on rather low-end hardware is a hard requirement.

I think of it as a particle system — each star is a little billboard — but each will be orbiting the center on a different path and at different speeds. Occasionally stars will change color (indicating their status in the game). What would be the most efficient way to do this?

• A single mesh (or, several big meshes), where I dynamically update the vertex positions (and sometimes color) every frame?
• A particle system which I somehow get low-level control of?
• DrawMeshInstanced?
• uh... running out of ideas here... something related to the new Jobs system?
• something else?

Thanks for any suggestions... I've never faced a problem quite like this in Unity before.

 

All stars will be always present (or so we can assume). But every star (particle) will be moving on every frame; I'd have thought calling SetParticles each frame would be a bit heavy.

But I'll give it a try!

 

you will run out of vertices very quickly if you render "millions" of stars as billboarded particles (4 verts each).

I beleive the Quest 2 can cope with around 900k verts max:

https://www.reddit.com/r/OculusQuest/comments/j32vaw/performance_analysis_for_oculus_quest_2_oculus/

You are going to need to solve that issue before you can realize what you want,

 

Well, millions was always aspirational. I'm doing 100k stars now, and that may be sufficiently dense for my needs.

 

Maybe you can render the far-away stars to a render texture so you don't have to render them every frame.

 

https://developer.oculus.com/blog/hybrid-mono-rendering-in-ue4-and-unity/

 

Why not group a few stars, like 2 stars on a single billboard? Some could be one star, some could be two stars, and other billboards could have three or four stars or more, on a single billboard. And then you can make them swirl around like a galaxy does.

 

You can, and that helps with vertex count, but you have to be very mindful of overdraw in the Quest. A single full screen transparent surface can be enough by itself for the frame time to get uncomfortably high (depending on the complexity of the rest of the scene). Two or three overlapping transparent surfaces and you’re going to be missing your frame time targets.