Simplify Colors / (Surface) Style(s)

The current definition of colors within IFC is rather complex.

There are different ways to define colors, i.e. through materials, through properties (very old), through specific entities (like sub-entities of IfcTessellatedFaceSet) and through inverse relations from any geometrical instance towards its styling.

Concerning the styling the structure of how to define the style is complex and could maybe be simplified. Also it is not totally clear if the style overrides a previously defined style what style is leading (this can for example happen in case of mapped items).

This is also a good moment to rethink the way to define colors. This is more a question to ISG members, but would it be possible / relevant to support ambient, diffuse, emissive, specular colors and RGBA / ARGB / RGBW / WRGB values as normally present in OpenGL / DirectX / VULKAN solutions?

The issue does not identify files, schemas, tests, or an implementation entry point. Start by locating the IFC definitions for materials, styling entities, mapped items, and related inverse relations, then establish the intended color model, supported channels, and style precedence with the ISG before implementation; done means an agreed, consistent simplified specification.

Written by the indexing model from the issue text.