Why SRP needs URP and HDRP separate?

If Scriptable Render Pipelines are supposed to just be primitive building blocks, opt in to what you need, etc., I am curious why we need a separate HDRP pipeline and package vs a URP pipeline and package? I am sure there is good architectural reasoning, but I feel like you could simply opt in to the high end stuff of HDRP (or not if you need mobile devices) and have all the architecture be a single render pipeline. It would make everyone's life a lot easier not having to support two render pipelines. Well maybe just asset developers lives, but still

 

It would also make people's lives easier if they need PC/console support and a version for switch/mobile. Alas, someone at Unity made the bad decision to make them separate. There are no good reasons for it other than that it was easier for Unity. Obviously, there are different systems involved in the rendering between HDRP and URP, but this is something that could have been abstracted behind a compatibility layer.

 

So long as URP gets plenty of investment, I'm good. It's looking pretty nice now - decals, flares, new rendering features etc.

 

The ability to make and bake your own pipelines was to be demonstrated by a couple of templates, from which folks could learn to make their own pipelines. LWRP and HDRP were to be these templates, at polar ends of the scale of targets.

Somewhere along the way, the templates became far more substantially essential to Unity proving everything about DOTS/ECS, and far too solidified, siloing became a problem, and they became too brittle to be mere demonstrations of SRP design and development, instead becoming PIPELINES in and of themselves!

As a side effect, the process of making your own SRPs got largely forgotten, and remains pretty much undocumented and untested outside of big teams doing special things.

And here we are...

 

And here we are. I used to want some unification but I've decided that Unity would cock that up more than just providing more features to URP.

So I'm just not going to die on that hill of Unified pipelines, don't think it's worth it MORE than buffing up URP.

If Untiy actually brought features like DLSS and FSR to URP, compute shader optimisations to rendering and some DXR they'd have 1 fully scalable URP pipeline for games and HDRP for movies.

This is less work than trying to make some kind if multi-pipeline nonsense in the same project, and have it stable. Cos URP and HDRP's feature sets are now far too far apart.

 

Exactly! It's where we are... and you've described the only sensible way forward... so long as they also divert a little attention to sustaining and supporting Builtin for those of us tragics stuck on it for the foreseeable future.

Sadly, because you've stated the obvious and sensible, I think this is the path least likely to be chosen by Unity.

 

The problem is when I talk about solutions Unity could take, it's for the present and the next year or so. When Unity invariably get around to it much later, it's just too late for that same advice to make any sense.

In the LWRP days / early URP, bolting that on HDRP would've made massive sense and still been small enough to achieve. Covering all bases.

But no, that did not happen. Instead a lot of time passed and the two pipelines have now drifted so far apart that it now only makes sense to for them to spend money on both pipelines.

There is no scenario on earth where I will maintain multiple pipelines in multiple projects for the same game, or switch between them because that's actually more work for me to get the most from, than switching engines and I think everyone knows that and doesn't want last-decade behaviour.

Solution? Throw cash at URP til it's minto!

 

I desperately need FSR for my VR development in URP. Developing in VR for HDRP is a fool's errand right now, so I'm really hoping we don't get left out for FSR integration. Would give me a ton of needed breathing room for VR development to push the visuals.

 

Well, URP is plenty fast for VR, I do use it for the same. The thing you would be missing is probably just volume lighting and you can fake that in VR to really good effect. What are you missing in your opinion? Latest URP 12 is a capable best IMHO.

 

i always thought SRP will be this super modular render pipeline where u can slot in features u need like a building blocks. But atm I have no clue what it actually is atm.

 

It's true URP has a come a long way from when it was just a poor version of the built-in renderer, but even today it's still missing many things

• Decal layers
• Volumetric Lighting
• FSR
• TAA
• Planar reflection probe
• Contact shadows
• Bent normals
• Subsurface scattering
• Hair/fur/cloth shaders
• Water shader/system
• Multipass shaders
• Impostors

to name a few

 

I only think contact shadows, TAA, FSR, volumetric lighting is needing SRP modification and the rest is achievable by people -- at least people have already done much of what you're asking for there (I guess the divide for me is... can it be done without SRP modification with ideal performance?)

In any case, it's come far and we should ask for more.