[Interest] [Qt3D][Android] Weird different performance on almost same class GPUs

Paul Lemire paul.lemire at kdab.com
Wed Dec 19 15:59:24 CET 2018

Hi Oleg,

Could you specify the screen resolutions of your phones as well please?
(I suspect they are lower than the tablet)

From what you are describing (moving further/nearer/multisampling) it
seems you are having fragment shader performance limitations.

You didn't specify what the benchmarks were doing, ideally you should be
looking at a fragment fill rate benchmark.

If that's the case, not much that can be done here apart from:

1) Simplifying your fragment shaders

2) Reducing potential overdraws (use depth testing, culling)

3) Generally speaking, trying to limit the amount of fragments

Since it seems you are using Scene3D, would you happen to have a
fullscreen QtQuick Rectangle underneath as a background? From past
experience,  this itself can actually put a bit of strain on the
fragment performance directly. (Using an Item + the window's clear color
might provide a work around).

Hopefully this can be of some help,


On 18/12/2018 18:43, Oleg Evseev wrote:
> Hi all,
> I have two phones:
> Qualcomm Snapdragon 400 MSM8928, GPU Adreno 305, OpenGL ES 3.0, RAM 1Gb
> Qualcomm APQ8064 Snapdragon S4 Pro, GPU Adreno 320, OpenGL ES 3.0, RAM
> 2Gb
> And one tablet:
> MediaTek MT8735, GPU Mali-T720 (1 core), OpenGL ES 3.1, 1280x800,
> Android 8.1, RAM 2Gb
> According to internet Adreno 305 and Mali-T720 have close performance.
> I run several 3d benchmarks and Mali-T720 (tablet) show better results
> than Adreno 305.
> Benchmarks of CPU MT8735 is twice better than  Snapdragon 400.
> But my qt application with Scene3D on tablet works much slower than on
> these phones.
> 3D scene is no so complex - just a skybox, 3d model, several lines and
> simple "ground".
> tablet FPS vs phone (any, they are quite simple) FPS:
> When camera far from model (far from it)
> 60 vs 50+ ( Adreno 305) (40+  FPS on Adreno 320)
> Making camera very close to model drop down fps to:
> 18-25 vs  ~45
> Enabling anti-aliasing (Scene3D multisample: enable) dramatically
> slows down tablet. Multisampling has almost no effect on phones.
> 8-10 vs  ~40 (camera is close to model )
> Without 3dmodel and other stuff only skybox almost same result on tablet:
> 60+ FPS without and ~25 FPS with multisampling.
> Working with Qt 5.9.5. I've tested Qt 5.12 - same result.
> Thanks in advance for any help or tips what to check.
> ---
> With regards, Oleg.
> _______________________________________________
> Interest mailing list
> Interest at qt-project.org
> https://lists.qt-project.org/listinfo/interest

Paul Lemire | paul.lemire at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel: France +33 (0)4 90 84 08 53, http://www.kdab.fr
KDAB - The Qt, C++ and OpenGL Experts

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