Just how big a deal is Batch by Shader?

I am still trying to evaluate URP in terms of when and if I should use it for projects. I honestly don't know much about this feature. The asset store has plenty of assets built around the concept of solving the issue of rendering speed and most involve the idea of trying to get less draw calls, usually by packing geometry with the same material into one model.

I have always hated this limitation and the idea of always needing to be concerned with draw calls. Is batching by Shader at the engine level the final answer to this annoyance? Can I now build the ultimate virtual dreamworld without any concern to how many gameobjects I am pumping out to the engine. Will the engine finally be able to optimise this for me?

If this is true I might just be fine with 8 lights per object (until deffered rendering?), since now my objects don't need to be merged into the same object geometry. I can deal with that and all of the other short commings of URP if I can finally not have to think about object batching as much.

BTW are there other limitations to the batching in URP? is it like batching SRP where it wouldn't batch objects with more than X (900?) number verts?

 

There is no, and never will be, a magic bullet that will fix draw calls. There will always be limits, and systems like the static batcher, dynamic batcher and SRP batcher are some ways to reduce draw calls. All of these have pros and cons, with good uses and bad. As a game developer, you'll always need to be mindful of this.

But from what I've seen, the SRP Batcher is pretty awesome, and is a pretty amazing batcher. I don't know the details, so I can't answer your final questions, but if you're really wanting to throw around thousands of meshes everywhere I suppose SRP would be your best bet :')

 

Hi @aleksandrk, I'd like to follow up on that because I'm looking into how the SRP Batcher can simplify our production pipeline and help optimize graphics performance.

- Just to clarify, the SRP Batcher only does static batching, right? (For some reason, this is never actually mentioned in the manual page here.) Does it have all of the limitations of static batching then, or is it somehow different?

- Batching-by-Shader is extremely interesting to us. Does it mean that texture atlases are now less important, because it doesn't matter if one big or several smaller textures (used by multiple materials that share the same shader variant) are passed over to GPU memory in a single draw call?

- The manual says that data persistence in GPU memory only works when material properties aren't changed at runtime. Some materials require dynamic per-frame updates (e.g., vegetation affected by wind). Is the SRP Batcher still efficient in such a scenario?

- Could you tell us how the SRP Batcher relates to GPU instancing? What would be a rule of thumb to decide between one or the other?

This is exciting stuff. Thank you

 

I see. In that case, why do you allow us (in the URP settings asset) to toggle on/off Dynamic Batching:


?

Cool, I'll watch this space. Thanks already for your answers!

 

Epic disagrees.

From my experience I have worse performance with the SRP batcher compared to legacy methods on iOS and Android.
My setup is all good, used the same shader variants everywhere possible, etc, not GPU bound, SRP batcher bumps my CPU usage past 16.7ms, which never happens with legacy methods.

 

It really shouldn't. "Actual graphics API" on Android is one out of three (OpenGLES2/3, Vulkan), and OpenGLES3 seems a reasonable default for most games on most devices at the moment. "Actual hardware" should also not have an impact on whether or not we use the SRP Batcher - that's kinda the point of using Unity in the first place, right? And when it comes to "actual content", OP said they use the same shader variants everywhere possible, so this should be a perfect use case for the batcher.

This is important - could you please help us understand if the SRP Batcher is or isn't a reliable way of achieving better performance on a vast majority of mobile devices? (Assuming of course its conditions are met, especially the one about having a very small number of shader variants.)