Cycles: Cuda 9.2 and 10 Issues.
Cuda92 has some issues with cycles, that shown most when rendering bmw2.7 gpu
I am sure we all hoped, that cuda 10 would fix this, which it didn't.
I played around with the usual suspects, aka don't inline this and even tried
disabling all inlining all together. didn't help.
then I played with the optimizers (both nvcc and ptax have their own optimizers
which you can independently control) and the issue seems to occur whenever you
call ptxas with O1 or higher (O0 makes a working, kernel) however there's no
documentation what optimizations O1 enables compared to O0 or anyway to enable
specific optimizer stages. so that turned out a dead end as well.
Then I figured if we know were the problem is we might be able to find a work
around. (my idea was to disable the optimizer for that one function, which you can't
for some reason , still it be nice to know where the issue is)
New problem: bmw27 has a lot of parts to it so after taking out various bits I ended
up with these 2 cases.
error.blend: matches the noise pattern you see in bmw27 it's a simple scene but there's
still a couple of mix shaders to it, simpler would be nicer..
error2.blend: no noise, but it renders completely black on the gpu, no fancy shader graphs
it's a straight up glass shader..
So I'm pretty sure it's something in the glass bsdf, but i don't know the code well enough
to look further into this.