Upcoming Qt switch to OpenGL ES on arm64

[bret curtis]

Hello Lisandro!

> Yes, that's a drawback we are not hiding. Applications needing Desktop OpenGL
> would be left out. But...
>

Sorry, but this is just not acceptable. There has to be another way.

>
> > If you say that arm64 has to be GLESv2 as well, then that is yet another
> > arch that OpenMW can't be built for.  Before the GLESv2 switch, OpenMW
> > worked just fine on arm* hardware, including the Raspberry Pi/Raspbian with
> > the VC4 mesa driver that has OpenGL 2.0 support.
>
> ...one thing is running and quite another is: how well does it performs when
> doing 100% CPU-based OpenGL? Are your users *really* interested to use your
> application when all drawing must be CPU-based?

There is a misunderstanding here and also in this thread. The Raspberry Pi has
the VC4 GPU which is hardware accelerated Desktop OpenGL 2.1 via the VC4 Mesa
driver.[1] This driver is fully open-source unlike the binary blob it comes with
that only supports GLESv2, but not via X11 nor Wayland.

So the only way to support Qt with hardware (not software) accelerated GL on
the RPi is with the VC4 mesa driver and Desktop GL.

As for OpenMW running on a RPi, it is fully hardware (GPU) accelerated via the
VC4 driver. It runs pretty darn well. You can walk around Morrowind (with mods)
right now at 25fps @ 1080p using a GPU-based VC4[1] OpenGL 2.0 renderer.
60fps in interiors. This is on a Raspberry Pi 2, likely better with the
RPi3 with VC4 being EoL, the next iteration of the RPi will likely be VC5/6
that is arm64.

> > I beg you, please either reverse the GLES decision in Qt or provide two
> > separate packages for GL or GLES support.
>
> I'm afraid providing two set ups is a non-go (alas, we would be doing that
> already and avoiding all this). And I don't there are many armel/armhf users
> with hardware Desktop OpenGL in their boards.
>

There are more than 5 million Raspberry Pis were sold as of February 2015. All
of them with a VC4 GPU, Raspbian ships with the VC4 mesa driver enabled!

I'm of the opinion that the switch away from Desktop OpenGL to GLES was a huge
mistake and should be reversed as soon as possible unless there is a way to
provide for both on all archtictures.

Cheers,
Bret

[1] https://github.com/anholt/mesa/wiki/VC4