After replacing the graphics card driver with 545.92, it runs perfectly
Yeah, that’s how it’s supposed to look.
I’ve also tested 552.22 in the meantime and that worked as well.
The scene_mdl_demo.txt is rather noisy because there are quite a number of lights inside the scene and the renderer only samples one of many lights per path vertex.
The vMaterials scene only has that one emissive mesh light.
I would also recommend looking at the GLTF_renderer which is quite a bit faster due to the hardcoded PBR material.
If you download some nice spherical environment lights from hdri-haven they can replace the default runtime generated environment texture with some real world images by drag-and-drop into the application window or from the start by the --env command line option. You can orient them with the Euler rotation angles inside the GUI’s Light panel.
(The intro examples can only load them with the --env command line and all examples using scene descriptions define the emissiveTexture inside the scene description for the environment lights instead.)