I have no idea (it wasn't exactly the same project, LuxCore vs Lux), and PBRT, on which Lux was based, later moved to full spectral rendering. I guess they fee

I have no idea (it wasn't exactly the same project, LuxCore vs Lux), and PBRT, on which Lux was based, later moved to full spectral rendering. I guess they feel they'd rather reduce register pressure a bit than support it.