For consistency, every section should have a "weight" parameter.

While working on the UI for 3ds max, I realize how inconsistent it feels that everything has a weight, _except_ emission and thin film.

I think _everything should have a weight_, even though this is just a multiplier in the case of emission and thin film, the UI consistency and the ease of explaining the functionality wins out, IMHO.

Also, since both thin-film thickness and emission luminance quite often have values outside the easily texturable 0-1 range, it is _extremely convenient_ to be able to set e.g. a high luminance value, but then modulate the intensity of the light by a 0-1 weight map, or to set a given thin-film thickness, and modulate the coverage of the thin film with a 0-1 weight map.

The only reason not to have them is parameter count frugality, but if most real-world use cases has users plugging in multiplier nodes in front of these all the time, I feel that feature should be built in.

Review the OpenPBR specification and reference implementation, focusing on how emission and thin-film parameters are currently defined and exposed. Determine the implications of adding weight parameters to both sections; done means the specification and implementation consistently support those weights and their intended modulation behavior.

Written by the indexing model from the issue text.