Question SpriteRenderer + shader properties override breakes SRP Batch

Problem: I use a bunch of sprites with same material and same textures (generated by sprite atlas) + shader graph sprite lit shader. In c# script i modify shader property and this breaks SRP batching.

What i want to achieve: I want to recolor my pixel art on fly, so i use a little trick: mapped texture + palette texture = recolored art. Palette texture is Nx1 size texture with sequence of unique pixels and mapped texture is a texture (which colors we want to restore from palette texture) each pixel of which contains value of where on palette texure we need to sample pixel. So in test project i have same atlas for everything. My shader have only 3 properties: _MainTex, _PaletteTex, _PaletteUV (float4). And all my sprites in scene has the same _MainTex and _PaletteTex (which is the same texture also because i'm using just one atlas for testing). So i see in Frame debugger that the only difference is _PaletteUV value, and this difference breakes SRP batching.

Why this confusing me?: there is label "SRP batching: compatible" in my sprite lit shader, but there is some information on forum that rendering sprites is a bit "special" thing and it breakes batching here and there. Also there is a reply from @bgolus

Question: What can i do with that? Have you any idea / same cases? I can any time generate tones of sprite variants and pack them into sprite atlas and render with sprite default material, but using shader is much much cleaner. Also i can try to use Graphics.DrawMeshInstanced, but i'll lose all this SortingGroup and other stuff.

 

To avoid breaking batching, you could send over your palette coordinate in a different way for instance through the vertex color. Note, SpriteRenderer.color says it is a Color but its really is Color32. There's also position.z if you're not otherwise using that value.

By using SpriteRenderer.color, you need to use a non-ShaderGraph shader because Sprite Lit and Unlit auto-apply that color with a simple multiply in such a way you don't have an option to disable it within Shader Graph.

 

I've ended up with writing my own sprite render system and 1 evening spent i've got my sprites rendered through Graphics.DrawMeshInstanced with different main and palette textures all in the same atlas and just for 1 instanced draw call.

 

How'd you end up handling the sorting groups?

 

I'm not quite yet there, for now i'm trying to understand how DrawMeshInstancedInderect works. I want to find clever solution about sorting group to be able to calculate sorting group + sorting order to global sorting order and then use DrawMeshInstancedInderect in the most optimal way.

 

Did you have success?

 

Not yet, but i move straight Yesterday i've came up with fact that i can't use ShaderGraph + ComputeBuffers, because second requires StructuredBuffer in shader and ShaderGraph has only OverridePropertyDeclaration -> HybridInstanced wich makes it compatible with DOTS MeshRendererV2 system and not actually generate any of StructuredBuffer (but MaterialPropertyBlock.Set[Type]Array works with HybridInstanced, and i can't figure out why). So for today i've planned to dive into writing URP compatible shaders from scratch.

 

https://github.com/sr4dev/Unity-SpriteAssist

I made this tool for SpriteRenderer + SRP Batch environment.
This tool converts a Sprite to a Prefab (internally it uses a Mesh Renderer).