@droettger Thank you so much for your extensive answer.
I definitely do have a problem with the stack size. When my resolution is 320 x 240, the problems are gone. If I am increasing it to 640 x 480, the rendering issues immediately return, but I can fix it if I am increasing stack size by a factor of 4 to 12000. As you have already mentioned, there is a new way in version 6.5 of setting the stack size correctly, but I am still studying the documentation and trying to understand the old and the new way.
As you suggested, I have tried to enable exception printing. Reading docs, I stumbled over this and added it to the code
m_context->setPrintEnabled( true );
m_context->setPrintBufferSize( 4096 );
As well as:
m_context["bad_color"]->setFloat( 1000000.0f, 0.0f, 1000000.0f );
m_context["exceptionErrorColor"]->setFloat( 1000000.0f, 0.0f, 1000000.0f );
Your Advise to change from “Sbvh” to “Bvh” seems to fix another issue. (Impressive that you saw it instantly)
optix::Group gro = context->createGroup();
optix::Acceleration acceleration = context->createAcceleration("Sbvh", "Bvh");
Now I can see another issue with light artefacts in my renderings. I did not manage to investigate into that problem yet.
So far I do not see any exceptions, but I am also not sure, if I have enabled all possible debug options in OptiX.