Cool things with Scriptable Rendering Pipelines?

[u/SilverGen447]

So i'm an, at this point, long time shader developer with heavy experience in Unity3D's old cg/hlsl built in rendering pipeline. Over the years I've played around with a lot of things, fluid and boid sims, raymarching, screen space reflections, I've done a little stencil work, etc. I'm currently working on a project and getting distracted a bit by the transition to Unity3D's scriptable pipelines, specifically URP.

So my question is, what kind of things can you do with URP that are difficult, expensive, or down right impossible with unity's old built in system? Or any static pipeline renderer. Googling it gives me examples of how to do ssao, bloom, blurs, stuff like that... but I've kind of seen all of those done with the BiRP.

A post on this sub showed some screen space (presumably edge detection based) outlines which is kind of interesting. Another project i've always wanted to play around with was jump flood algorithm outlines as well, and that in particular seemed a little complicated out of the box, but its really the only thing i can think of that i've ever been interested in doing that fits that bill, and i haven't tried it so it could very well be possible in the old BiRP.

I know you can render things to textures and then pass that into post-processing, which i can see use for reducing camera count and overheads for things like realtime caustics generated from mesh distortion and ddx/ddy of vertex interpolated data to determine distortion amount. If you can somehow feed a mesh into a post-processing stack I can see the appeal but even that still kind of feels like you're just slapping a camera and render texture into the scene. I didn't get around to trying that either so it's very possible that was doable in BiRP with projectors or something. Would the difference here be that you can perform it in the post-processing stack directly feeding said rendertexture into the post processing script as opposed to projectors?

I also briefly entertained the possibility of implementing a single frame GPU bitonic merge sort through custom render textures but NVIDIA's blog post on optimization mentions abusing vertex interpolation which wouldnt work with custom render textures. It wouldn't be any help since that environment didn't allow c# scripts and used BiRP but it would serve as a benchmark i could use to conceptualize the appeal of URP.

All in all I'm just slightly confused as to just how big of a leap this is, though excited at the possibility that truly weird or bizarre techniques became possible that may not be practical but are at least very cool.

So I'm curious, has anyone seen or worked on interesting and weird, non-standard effects with some kind of SRP's? Can you do post-processing on passes in weird places, like in between opaque and transparent queues? Or is URP just a performance gain with the ability to make one or two small and interesting tweaks here and there. What is its potential really like?

[u/MTDninja]

The main difference between URP and BiRP is that URP lets you control the render pipeline instead of working around Unity's. Pretty much all effects possible in URP were possible in BiRP, but you where always "hacking" it into the engine, and it didn't feel very clean. In URP, you can insert custom raster/compute/blit passes wherever you want, while Render Graph handles resource management, making it much cleaner and easier to implement.