As a Roblox developer, it is currently impossible to have multiple Roblox materials on a single union. Support for multiple colors on a single union has been a thing for awhile, but we are still limited to one material per union.
Say for instance, you want to have a red brick wall that has a gray cobblestone wall on the inside
(Done here using visual trickery):
This issue has particularly irked me with my attempts to port maps from the Source engine into Roblox. Geometry in the Source engine tends to use multiple different surface materials on a single solid, and this has resulted in mixups between what material the surface is supposed to look like, and what it actually looks like:
Thus, I’d like to propose support for multiple materials on a single part in CSG.
This would require the implementaton of the following property for legacy support:
Property bool PartOperation.UsePartMaterial
It would act as a parallel to UsePartColor, but with the materials of the part instead of the colors.
This change would improve the visual fidelity of CSG, and reduce the number of parts needed to have surfaces with seemingly multiple materials.
While I like this idea in general, is it even possible with Roblox’s engine to actually allow this to happen? Wasn’t there some physical limitations to union operations, or am I being daft.
If you’re considering things like how the materials play into the physical properties of the object, then yeah there might be a weird edge case there. Ideally this would just be a visual thing though.
This might reduce efficiency / performance but the fact that it is a bool property should make it fine, as long as they implement it only when that property is ticked, and not do some weird stuff like they did with outlines where it still results in like a massive performance decrease even when it’s off.
If they really care about the physical properties, they can probably estimate the mass of the object by calculating how much of the total surface area each material takes up, then they average out the physical properties by the volume of the object and the percentages that each material takes up.
