AFAIK, LightWorks in ArchiCAD only supports using an alpha channel for a bump map (or displacement)...?
You're needing a map to define reflectance, which you can do in Artlantis 3 which supports grayscale maps for: reflection, shininess, bump, normal and transparency. (Other advanced rendering engines support these things and more, of course.)
Cheers,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sonoma 14.7.1, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB