Matt Pharr

Here we go: the answer is that the error is correlated but there's still error: 63 spectral film buckets, 63 spectral samples, "independent" sampler: Same deal, using a different RNG...

Should be fixed in ebd7bfa1a7e22b6cc0f2637b0aa9253f5a2f1dc8.

I don't know anything about Metal so can't say. What is the state of apple's C++ support on the GPU?

For NVIDIA GPUs, almost all of pbrt's rendering code (sampling, light source models, BSDF evaluation, etc.) runs on the GPU; it's almost entirely the same code as runs on the...

Thanks for reporting this! Should be fixed now.