Did anyone discussed here about integrating Pixar's Hydra as a GL backend for Gaffer?

[Hradec]

Hydra seems like a pretty impressive deferred realtime renderer used by Pixar on Presto. It's a really nice render engine, since it implements a lot of the tecnology used on games, which allow for things like realtime ambient occlusion, depth of field, etc,

as an example, this year Pixar is presenting they improvements on realtime hair rendering on Hydra:
https://vimeo.com/283773316?ref=fb-share

this is a pixar presentation of it from 2 years ago, when they released USD. It shows what Hydra can do:
https://vimeo.com/180966864

although I don't known how much of the deferred goodness is actually open sourced, the fact is Hydra is deferred like a game engine, so we can develop all sorts of graphic pipeline with it, without touching Gaffer.

Although the USD code for hydra doesn't seem to be using Vulkan yet, it has some references to Vulkan inside it. So I'm not sure if they may be preparing the code to switch to Vulkan, or if the open sourced code has Vulkan stripped out... (I think that is one of the questions to be asked at Siggraph this year! :P)

But, for studios who are adopting USD as the main agnostic file format, I suppose it would be perfect... Gaffer as a open source "Presto"!

thoughts anyone?
Hradec

[Chad Travis]

Katana uses Hydra for it's viewport. So, considering how similar they are, I'm guessing it would be ideal for Gaffer as well.

[Sachin Shrestha]

USD gathers more steam as RodeoFX open sources their production solution Walter:

https://github.com/rodeofx/OpenWalter

https://www.rodeofx.com/en/news/walter

It includes an Arnold procedural as well.

Cheers,
Sachin

[do...@image-engine.com]

Chaps!

Thanks for the links & suggestions.

We've looked a Hydra a little and I would like to investigate it further. It wasn't easy to work out what SceneDelegates had to provide to get materials, lights & shadows working with hydra, but I hope it's easier to get these features going in the latest release of USD.

I think we'll also consider other approaches, like the Filament renderer open sourced by google recently and other viewport optimisation approaches like a raytraced viewport. I don't think anything has been decided but I hope I'm not too bold in saying we hope to focus on the viewport performance and features in the near future.

Cheers
- Don

[Alex Fuller]

And I hope I'm not too bold but I want to put my hand up about doing some cool viewport stuff myself.... :)

Where did you hear that Hydra is a deferred renderer Roberto? To be honest having control over building some kind of render graph via gaffer nodes would be pretty cool, to composite any kind of renderer approach that way (if you see DICE's frame graph presentation this gives you an idea of a render graph).

Cheers

[Sachin Shrestha]

To add my 2 cents here - I don't know how deeply IE is integrated with an Arnold pipeline but since the open source gaffer version has a quite tight integration I'm assuming that you guys are completely using Arnold for all your shows. So, perhaps it may be a good idea to also provide an Arnold Viewport mode similar to what Maya is now doing with 2018 natively (or what Arnold Viewer did with the MtoA plugins before that with 3D manipulation option within the viewer). The experience of navigating within a 3D "render" viewport similar to clarisse while iterating your work is a great productivity toolset for artists as they are immediately looking at the final pixels. This would mean enhancing the current Catalogue/Display node to allow 3D manipulation within the render viewer. Currently we have to split a panel into a display panel and a viewer panel and because we can't tear off panel's yet, managing the screen real estate with both the viewer and display can be cumbersome. A completely interactive 3D render viewport would help alleviate some of those issues. Raytraced viewports like embree are great but the user would still be further away from the final image especially since gaffer's direct use-case is more towards lookdev/lighting.

Of course, I may be oversimplifying the amount of work involved to get this working in gaffer with support for all renderer backends but thought I'd throw this idea out here and see if it sticks ;)

Cheers,

Sachin

[John Haddon]

Hi Sachin,

Arnold-in-the-viewport is something I'm really keen to have, and I've been gradually moving things in that direction while working on the async viewer stuff. The main missing piece is doing object picking from renders, which would be a really nice feature in its own right anyway. I should also point out that while I said Arnold-in-the-viewport, the way we'd implement this would allow any supported renderer to be used, so would work for 3Delight and Appleseed as well.

Cheers...

John

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[Chad Travis]

Could you just have the renderer return a cryptomatte and use that to pick objects from the render? I'm sure there'd be problems with this most likely, but just an idea. :)

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[Sachin Shrestha]

I'm stoked to hear that John! And I'm glad I wasn't crazy to expect that :) Hydra and embree look great but I strongly believe that in gaffer's lookdev and lighting context (or any dcc that is lookdev/lighting facing) it makes more sent to look at the final pixels. If users actually only wanted to see gl type basic shading representation then they could simply switch to the classic viewport or we could have options similar to the Arnold Viewer with various preset modes like basic, uv, occlusion, etc. I totally agree about the object picking workflow. Its certainly saved me a lot of headache when debugging some gnarly scenes with only baked standins in Maya and artists also seem to use it frequently to select related materials, etc.

Cheers,

Sachin

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[John Haddon]

Yeah, that's the sort of thing we were thinking - I guess the other alternative would be to actually fire a ray and see what it hits. I'd like to get the deep image stuff merged before we start thinking about cryptomatte though, so we can use deep samples to store the multiple ids per pixel, rather than being stuck with a fixed number...

Cheers...

John

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[Alex Fuller]

I think there's still room for a hybrid renderer of sorts which could possibly disassemble OSL bytecode and make GLSL on the fly, with either Nvidia RTX or Radeon Rays via Vulkan for indirect and shadow rays as an option, but that could be more of a particular renderer idea that Gaffer could just interface with and use as an alternative viewer (combine google's filament with RTX for example). 

Having a 100% raytraced but simple non-GI renderer would have a major advantage over a raster viewport still if you just wanted to view large amounts of un-optimised instanced geo like typical VFX workloads, similar to Clarisse...

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