surface luminance node with Arnold GPU not supported?

[Neopork]

I am creating a model of Earth and I am trying to add sunset colors to the clouds near the terminator (transition from light to dark). It is working in the image below which is using CPU rendering. I was able to achieve this effect using the surface luminance node and a gamma correct to adjust the falloff. I do most of my rendering with GPU, but this setup with surface luminance does not appear to work with Arnold GPU on Arnold 6+. I didn't see anything in the GPU limitation documentation about this node but I can tell if I switch between CPU and GPU that something stops working while using the GPU.

Can anyone confirm that this is not supported under GPU, identify the issue with my set-up, or provide an alternative method that will work with GPU?

Thanks in advance!!!

-Neopork

twitter.com/@Neopork85

graph.pngpic.jpg

[Stephen.Blair]

SurfaceLuminance is converted to a Utility shader (in Lambert mode) connected to an rgba_to_float node (in Luminance mode).

The Luminance mode seems broken on the Arnold GPU, it's returning black.