Add Liquid Glass

[TLabAltoh]

Implementation of Liquid Glass. The following URL may be helpful... ?

https://www.shadertoy.com/view/wccSDf

[TLabAltoh]

branch: experimental-liquid-glas

liquidglass.mp4

[TLabAltoh]

Current Issues

• Rendering uses 3 passes (shadow → glabpass → graphic/outline). A dedicated separate shader is used only when the liquid glass effect is effective. ← I've thought about it a lot, but maybe there's nothing we can do about this?
• Blur effect not yet implemented
• No compatibility with URP (Implementing Grab Pass in URP seems like hard work...). It would be great if Unity had a dedicated preprocessor that could identify the rendering pipeline...
• Forgot to sample MainTex

The URP issues are too serious, so I think we'll limit Liquid Glass support to BRP for now.

[TLabAltoh]

[TLabAltoh]

Memo: Blur Implementation

Currently considering blur implementation. When implementing blur for SDFUI's Liquidglass effect in BRP, it's necessary to process GrabPassTexture with a single-pass Gaussian blur. However, based on my research, single-pass Gaussian blur appears to be a heavy process, so I'd like to avoid using it.

Considering performance and parameter flexibility, I want to use GrabPassTexture processed with a 2-pass Gaussian blur (vertical and horizontal passes), but in this case, the blur effect would be applied to the entire rectangular mesh that renders the SDFUI.

The solution I'm currently considering is implementing a custom SRP to create an alternative to GrabPassTexture offscreen (OffscreenGrabPassTexture). This would allow using 2-pass Gaussian blur while enabling OffscreenGrabPassTexture sampling only within shapes defined by distance functions. However, this seems like it would be a significant amount of work.

My current goal is to create an SRP based on URP that supports OffscreenGrabPassTexture creation (if successful, it might be achievable with a relatively small amount of code).

However, I'm starting to question whether it's necessary to be so particular about implementing Liquidglass blur effect.

For Liquidglass-compatible sources, it might be better to operate them separately from the main branch for now. It would compromise the project's compatibility as a package. But I'll try implementing it once anyway ...

[TLabAltoh]

It looks like implementing a custom SRP is more difficult than I thought.
​I'm thinking that instead of using ScriptableRenderContext.DrawRenderers(), I could use CommandBuffer.DrawRenderer() to implement custom logic before and after drawing each renderer, such as creating a GrabTexture. However, I haven't figured out the specific implementation details yet.
​For now, I'm giving up on the custom SRP and will investigate whether it's possible to draw materials that use the Liquid Glass effect as a post-process.

[TLabAltoh]

https://gist.github.com/hadashiA/4e37d2f42dd376d50f57ebd6311121eb