Resolved URP Cached shadows

I know a lot of folks who would love to have Cached Shadows in URP. This feature is in HDRP, but is not on the URP public roadmap and I have not heard of this in a while. Is it planned?

We ourselves implemented it and the gains from it are truly non-negligible.
The additions of Renderer.staticShadowCaster and ShadowObjectsFilter.StaticOnly/DynamicOnly in 2021.1 make it even more worthwhile to have dynamic + static shadows on the same light.

 

Also want to say that we have had this in a couple years now in built in RP because we wrote our own system for it. It's a total deal breaker on mobile without it. So definitely would love to see this come to URP also. But it's gotta be a performant solution with adjustable settings, not some "one size fits all".

 

Hi @Elvar_Orn
Also, is there any plan to support shadow rendering that can be shared between cameras in general SRP? Like a ShadowManager that collects every camera's shadow requests and process them so that no shadow view is rendered twice?
The biggest example of this would be multiplayer splitscreen where sometimes punctual shadowmap from the same light are needed.

 

Hi Elvar are you able to share if that is planned for the near future yet?

Thanks!

 

Hi @Elvar_Orn ! I couldn't find this feature on the Unity URP rendering roadmap. Are cached shadow maps still on your priority list?
In Unity 2022.2.x there is a Static Shadow Caster toggle on mesh renderers in URP but apparently it doesn't do anything at the moment.

 

Really appreciate the feedback @Elvar_Orn! Sounds like a great plan! Thank you! ✌

 

Any updates to share? :' )

 

Uhu! That's great to know @Elvar_Orn ! Thank you so much for the feedback! Really useful to at least get a feel of the roadmap ahead. Much appreciated! ✌

 

Thanks @Elvar_Orn for the updates!

Would it be possible to add this cache on the centralized Unity-roadmap? We may be able to help by submitting a report on the "How important is this for you?" form.

Our application runs in WebGL in URP. The sun and the scenes are static most of the time. Caching all these shadow-maps would be a huge deal, especially for our clients on low-end devices and on mobile.

Again, thank you for pushing this feature!

 

is there any news?

 

Thanks!

 

Are you literally the only person working on URP? Why Shadows improvements are bottlenecked by Shader Variants?
I've only now realized that Static Shadow Caster is HDRP only feature, but is visible in URP since 2021 and does nothing. What a confusing joke.
Not to push on you specifically, but it's just ridiculous how much time it takes for any basic features to come out.

Shadows are the most pain right now, they need both performance and quality. You can't look at them without tears of pixelated jitter and bias artifacts (especially when back side is translucent / light wrapped). And my GT 740m can't handle even 6 spot lights with low shadows, not mentioning point lights.

Now, let me dream for a moment. There is so many different rendering techniques that URP could have, to satisfy all kinds of use-cases/needs, performance targets, and make some games an actual possibility.
Just to name a few:

- SDFs that can be used for ANYTHING -- 10KM soft shadows with full GI, distant-impostors, metaballs, collisions/physics on GPU for VFX or gameplay. You name it! Graphics - Erebus - Real-Time Ray Tracing SDFs; UE4/5 Style DFAO and Soft Shadows [HDRP/URP/BUILT-IN]
And it seems that there was some work done already with mesh-to-SDF, but it needs to be much more focused on, as it's the most promising universal solution for many problems that is relatively cheap. Unity-Technologies/com.unity.demoteam.mesh-to-sdf: A light and fast real-time SDF generator.

- Old-school stencil shadows https://github.com/rhedgeco/UnityShadowVolumeGenerator

- Virtual shadows akin to tile-based lighting. HD | Tile-based Shadows (hd-prg.com)

- Dual Paraboloid Point Lights (implemented in Godot) or Reflection Probes. So I got dual-paraboloid 97% working.. would you gurus co-brainstorm with me for the last 3%? - Unity Forum

- Capsule Shadows (under consideration for HDRP? well, since 2022..)

If only Unity invested a few banks of beer at R&D...

 

I've been wondering why Unity never went for Variance Shadow Maps instead of PCF. I'm not exactly an expert on this topic, but everything I've read suggests that the shadow quality is way better, even with smaller shadow map resolutions.



https://graphics.stanford.edu/~mdfisher/Shadows.html
https://developer.nvidia.com/gpugem...ws/chapter-8-summed-area-variance-shadow-maps

 

Here's a document demonstrating many different shadowing techniques and occuring problems, including all VSMs:
Advanced Soft Shadow Mapping Techniques (nvidia.com)

Looks like it's not even hard to implement! And performance should be much faster, since it's only 1 fetch per-pixel, + they eradicate bias artifacts and aliasing thanks to blur. (yet might look weird, expanded, incorrect.. or lets say - stylized )
All types of VSM suffer from light bleeding inside fully-shadowed penumbra (which is especially noticable with translucency), which can be mitigated with some sorts of clamping/threshold, or by using Layered VSM.

Here's an old implementation of VSM:
gkjohnson/unity-custom-shadow-experiments: A few custom shadow implementation experiments within Unity (github.com)


- Default Lit, looks ok?

- Translucent material, oh gosh.

> Extreme Expansion, bruh

And why, would you look at that! They've attempted to make it in SRP long ago!
ScriptableRenderPipelineData/ShadowMoments.hlsl at master · Unity-Technologies/ScriptableRenderPipelineData · GitHub
And now this code exists only in HDRP?? Is it even used?
Graphics/ShadowMoments.hlsl at master · Unity-Technologies/Graphics · GitHub

 

Ask this during the graphics blitz day (;

 

Thanks for your continued work on all this, we appreciate it. Much as someone else mentioned in this thread above, I'm interested in why URP wouldn't use Variance Shadow Mapping, or even EVSM, it really can work wonders for really soft shadows. (They aren't physically accurate, but that's perfect for URP) It's even pretty performant, see the slides I've linked below which show how it's used in roblox of all things. (Clearly that makes it fast enough for most hardware URP targets)


I think the stuff on shadow casting starts around slide 40
https://ubm-twvideo01.s3.amazonaws....ering_Roblox_Vulkan_Alhuwalia_Maya_slides.pdf

 

VSM / EVSM / ESM is worthless for your main directional light, although it can be much more useful for special use cases (point shadows, and even then, still some drawbacks). If it really were the great solution like it seems on paper you would see it in way more games. I've implemented quite a few variations and it has way too much light bleeding to be usable on medium and bigger light sources.

COD Warzone does use ESMs (iirc) for point shadows though, so definitely some good use cases there.

 

I see your point, but I'd like to argue the oppsite specifically for the case of EVSM on a directional light. All VSMs have light bleeding issues, it's true, but a good EVSM implementation with a bit of over darkening to hide any remaining leaks can work wonders. Don't take my word for it though, take a look at the slides I linked earlier for implementation details, and for an example of it working very well for pretty general use cases, just mess around with roblox studio. It's not perfect, but it's surprisingly performant, and has very soft, good looking results. Just not having to deal with the performance, quality, and bias issues of PCF and standard shadows makes it a win for me honestly.

(As a bonus it even works with anisotropic filtering, which is pretty neat)

 

If I am not mistaken, EVSM requires at least 2 maps (or channels), and up to 4 for better quality. More info here : https://gamedev.net/forums/topic/663139-evsm-is-the-best-needed/5195302/ and here : https://www.martincap.io/project_detail.php?project_id=9

So performance is going to take a big hit from memory reads alone. I think in some ways memory performance would be improved a bit because you could use mipmaps, but then again you also have to generate the mips and do the blurring. A lot of options with shadow maps open up of course when you aren't so performance limited.

 

Not really, a four channel read in one, single texture sample is way less expensive then something like a 9 (or more) sample PCF. While VSM's are more expensive at low filter widths, they quickly eclipse PCF's performance at any reasonably soft kernel size. (See the chart towards the end of this article, figure 8-13)

You absolutely aren't wrong about increased VRAM usage though.

https://developer.nvidia.com/gpugem...ws/chapter-8-summed-area-variance-shadow-maps

 

I just hope it doesn't take another year or so to get some decent improvements. I'd much prefer to have something useful right now, rather than 'complete' but at undefined point in a looong future. (It wouldn't hurt much to make improved shadows first, and then move them to a newly developed framework, right? Could be a nice test of portability for such system)

 

I have now bought https://assetstore.unity.com/packages/tools/particles-effects/corgi-cached-shadows-for-urp-246936.
I needed it for getting fast "realtime" shadows on Quest 2/3. Works out of the box and the implementation seems pretty straightforward. For sure it would be nice to distinguish between (cached) static and dynamic meshes. But for the moment I can life with this.

 

Hi, has there been any updates on this? could really use cached shadow maps on URP

 

On the asse4 store

 

The author stated that the cached system is meant to be used for games where the dynamic objects use fake shadows. I still think it would be great instead to have the option to differentiate, one day I will need to dig into it.

 

Maybe I should have been more precise... I'm totally fine with Corgi's solution for the moment. But if Unity would implement their own cached shadow system it with a distinction between cached static geometry and per-frame dynamic one, that would be perfect!
As stated previously the MeshRenderer component has already a (unused in URP) flag called "Static Shadow Caster" that is meant for such a system.