this doesn’t work for me if the input is a lerp between 2 values, I want to go from 27000k to 1850k, this must be a bug surely?

I used the BlackBody node just recently on a 4.9 project without any problem, do you mind posting a screenshot of your graph so I can try it on my end? I’ll let you know if it works for me.

can’t right now, but since I posted this I noticed it was only failing because of the lerp alpha I was using, which was the dot product between a vector and pixel normal, clamped between 0 and 1, this failed whether it was built using nodes or “clamp(dot(PixNorm, LightVec), 0, 1)” in a custom node

it doesn’t give an error, just renders the preview with the checkerboard surface as if it’s failing to compile

I think it might be the same problem as this?

yes could be