[Development] Shaders in QRhi

[Paul Tvete]

QRhi is not only the foundation for Qt Quick 3D. Qt Quick (qtdeclarative) is also built on top of RHI. In addition, Qt Multimedia and Qt Widgets use RHI.

In short, QRhi is going to be supported and actively developed for as long as Qt exists in anything similar to its current form. The only limitation is that we do not provide a binary compatibility guarantee, so any application that uses RHI will need to be recompiled when switching to a different minor version of Qt. We also reserve the right to change source compatibility, but given its widespread use within Qt, that is unlikely to happen.

Cheers,
- Paul
________________________________
From: Development <development-bounces at qt-project.org> on behalf of Harald Vistnes <harald.vistnes at gmail.com>
Sent: Sunday, December 22, 2024 1:30 PM
To: Giuseppe D'Angelo <giuseppe.dangelo at kdab.com>
Cc: development at qt-project.org <development at qt-project.org>
Subject: Re: [Development] Shaders in QRhi


Thanks, this looks reasonable given the differences in the backends for these shaders.

More general, is there a commited roadmap for QRhi? Is it "safe" to start using it in applications with a long lifetime, or can we risk it being deprecated and development stopped like Qt3D? Since it is the foundation for Qt Quick (3D) I this risk to be reduced. But is it being actively developed and improved?

I am still considering which library to replace Qt3D with. Quick 3D is not an option. Vulkan is an obvious candidate, but it would be nice with  D3D and Metal support as well, and it is so low level. Bgfx is a nice alternative, quite similar to QRhi, but mainly driven by a single developer, which makes it risky. So QRhi currently looks like a good option. What are good arguments for _not_ going for QRhi?

Thanks,
Harald

lør. 21. des. 2024, 11:32 skrev Giuseppe D'Angelo via Development <development at qt-project.org<mailto:development at qt-project.org>>:
Hello,

On 21/12/2024 09:18, Harald Vistnes wrote:
>
> I've seen some notes that geometry shaders are not supported in QRhi,
> but I don't know if that is outdated or not. Can geometry and
> tessellation shaders be used with QRhi?

Yes, although with lots of limitations, and they're still
half-experimental so YMMV.

See the descriptions of QRhi::Tessellation and Geometry at
https://doc.qt.io/qt-6/qrhi.html .

Thanks,

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Giuseppe D'Angelo | giuseppe.dangelo at kdab.com<mailto:giuseppe.dangelo at kdab.com> | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
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