Qt [c++] - No Qt3D rendering on older laptop

kevin_d

Hello Folks!

I developed a game which uses the Qt3D Engine to display a custom 3D scene.
I was now copying the programm on an older Machine (Win11, i5, 4GB Ram) and the program starts properly.
Unfortunately, the 3D Scene is not rendering (the QT3D widget remains empty).
I also installed some OpenGL drivers from Microsoft [https://apps.microsoft.com/detail/9nqpsl29bfff?hl=de-DE&gl=DE]

What am I missing to set up for Qt3D to render a scene?

best regards, kevin_d

kevin_d

btw, the System has Intel HD Graphics
Drivers: igdumd64.dll and igd10umd64.dll

8Observer8

Try this:

extern "C"
{
    __declspec(dllexport) unsigned long NvOptimusEnablement = 1;
    __declspec(dllexport) unsigned long AmdPowerXpressRequestHighPerformance = 1;
}

kevin_d

Hi!
Thanks for the tip. Unfortunately, that did not do the trick.
According to https://forum.qt.io/topic/50936/qt-5-4-sending-qdebug-to-a-file-40-aka-logging-41-solved/5, I am tracing the warnings, which say:

{Warning:} D3D11 smoke test: Failed to create vertex shader
{Warning:} Initializing RHI with DirectX backend
{Warning:} RHI: Unable to use requested RHI Api, trying to fall back on OpenGL
{Warning:} Initializing RHI with OpenGL backend
{Warning:} QOpenGLContext::makeCurrent() called with non-opengl surface 0x190509c29d0
{Warning:} QRhiGles2: Failed to make context current. Expect bad things to happen.

My DirectX Version is locally at 12

best regards, kevin_d

kevin_d

hi!
On a working machine, i get a "WARNING - Initializing RHI with DirectX backend" ...
I also installed additional DirectX-components according to https://www.microsoft.com/en-gb/download/details.aspx?id=35, but it fails nevertheless.
~kevin_d

KH-219Design

I was intrigued enough by the posted RHI warning text lines that I thought I would poke around in Qt source code for clues.

Disclaimer: I do not currently work on any program on Windows (nor DirectX specifically), so I have not attempted to reproduce this nor to run anything on Windows at all at the moment.

Based on reading source code, (and depending which Qt version—here I have assumed 6.10), it seems like in order for this to happen:

{Warning:} Initializing RHI with DirectX backend
{Warning:} RHI: Unable to use requested RHI Api, trying to fall back on OpenGL

The Qt method bool QRhiD3D11::create(QRhi::Flags flags) has to return false.

You can see the body of the method here: https://github.com/qt/qtbase/blob/v6.10.2/src/gui/rhi/qrhid3d11.cpp#L197-L419

This suggests at least two potential paths toward a deeper diagnosis:

Make sure Visual Studio has access to Qt framework debug symbols and source code, and step through QRhiD3D11::create in a debugger.
Try to write a (non Qt) small DirectX "hello world" that uses functions like createDXGIFactory2 and dxgiFactory->EnumAdapters1 (which are the functions that Qt is trying to use under the hood).

In option (2), the idea is that if you directly write some DirectX code (in a separate main that does not use Qt at all), then you can perhaps more quickly discover what part of DirectX is failing to cooperate.

I offer this in the spirit of brainstorming. Again, I am not actively developing any Windows/DirectX codebase at the moment, so my advice is certainly not "expert" in that regard. However, I have done such work in years past, and I have used the approaches (1) and (2) successfully in the past to debug similar scenarios where it was not clear to me whether Qt was misbehaving or whether something nested "underneath" Qt was misbehaving.

kevin_d

Hello!

Thanks for your reply.
Appearantly, the Graphic Chip does not support DirectX11 ...
Is there a way of a fallback to either OpenGL or DirectX10 ?

best regards, kevin_d

SGaist

Hi,

I think you can use the QSG_RHI_BACKEND environment variable for that.

kevin_d

Hi!
So... no chance for Direct3D10 ?

best regards, kevin_d

SGaist

Based on a quick look at older versions of the documentation, I would say no.

kevin_d

Hmm, i would fancy to have a fallback on OpenGL, when having no D3D11 ...
But it says: QOpenGLContext::makeCurrent() called with non-opengl surface ...
What does it mean? Can it be fixed?

best regards, kevin_d

SGaist

Does it happen if you set QSG_RHI_BACKEND before starting your application ?

kevin_d

I am not using QQuickWindow, but instead Qt3DExtras::Qt3DWindow

SGaist

In that case you might be able to leverage Q3D_RENDERER. See the module documentation for more information.

kevin_d

I did that. My output is:

WARNING Initializing RHI with OpenGL backend
WARNING No GLSL shader code found (versions tried: QList(130, 120) ) in baked shader QShader(stage=0 shaders=QList(ShaderKey(1 Version(300 QFlags()) 0)) desc.isValid=true)
WARNING Failed to build graphics pipeline: Creation Failed

No problem with this setting on the newer machine so far ...
Speed of the scene is comparable to DirextX11+

What am I missing?

8Observer8

It looks like you are running into a classic RHI (Rendering Hardware Interface) mismatch. Even though the performance feels snappy, those warnings are red flags that your current environment is missing the specific shader translations needed for the OpenGL backend.

Here’s the breakdown of what is actually happening under the hood:

1. The Shader Version Gap

The error versions tried: QList(130, 120) tells us that your application is looking for older, "baked" GLSL shader code (OpenGL 3.0/2.1 era). However, the only shader found in your binary is Version(300), which corresponds to OpenGL ES 3.0.

What you're missing: Your application was likely compiled/packaged with shaders targeting modern mobile or DirectX/Vulkan backends, but the runtime is falling back to a legacy OpenGL path that doesn't have the corresponding "blobs" to talk to the GPU.

2. Why it "Works" on the Newer Machine

The newer machine likely has a more robust driver set or a different default RHI priority.

DirectX 11 vs. OpenGL: On Windows, Qt and similar frameworks perform significantly better on DirectX because they can use the ANGLE layer, which translates OpenGL calls to DirectX.
The "Speed" Illusion: If the scene is still fast, your system might be successfully falling back to a software rasterizer or a partial hardware acceleration path, but you'll eventually hit a "Black Screen" or a crash when the app tries to call a specific graphics pipeline that failed to build.

Comparison of Backends

Feature	OpenGL (Legacy)	DirectX 11	Vulkan / Metal
Stability	Lower on Windows	High (Windows native)	High (Modern)
Shader Format	GLSL	HLSL	SPIR-V
Compatibility	Hit-or-miss drivers	Best for Windows	Best for Cross-platform

How to Fix This

You likely need to force the application to use a backend that matches its baked shaders. Try one of the following:

Force the RHI: Set an environment variable before launching the app to see if it clears the warning:
QT_RHI_BACKEND=d3d11 (For Windows)
QT_RHI_BACKEND=vulkan (If supported)
Update Drivers: Even if the machine is "older," ensure the GPU drivers support OpenGL 3.3+.
Check Shader Baking: If you are the developer, ensure your qsb (Qt Shader Baker) settings include the desktop GLSL versions (--glsl "130,120,100") and not just the ES versions.

Note: The "Failed to build graphics pipeline" error is the most critical. It means certain effects, materials, or lighting calculations simply won't render, even if the rest of the UI seems to be moving.

Would you like me to show you how to check which OpenGL versions your current GPU drivers actually support?

P.S. Sorry, but my answer above was generated with Gemini. I think it can be usefull.