Double Sided per Material

[DoobesURU]

This is my WIP solution to issue #255 . The goal is to give the Age builder the option to set double-sided by material instead of by entire objects.

To do:

• Fix toolbar buttons so they can work with the new Plasma material panel option, which isn't working yet, probably due to multiple materials being on objects and multiple users of materials.
• Fix an issue where the exporter runs into lighting_mod.unleashed .
• Possible conversion option to bring mesh double sided over to new material double sided, whether automatically or manually via button.

Again, this is my (admittedly clumsy) attempt to fix this issue as I believe it aligns more with how Cyan's plugin did things based on observations. It would keep extra materials from being needlessly set to TWOSIDE and possibly be a slight improvement in performance.

[Hoikas]

Blender uses bpy.ops.material for material operators instead of bpy.ops.mat.

[Hoikas]

Unfortunately, MATERIAL isn't a valid object type. It might be easier for us to chain the material slots, so something like...

        mat_list = [slot.material for slot in itertools.chain.from_iterable((i.material_slots for i in context.selected_objects)) if slot and slot.material]

(Warning: untested)

[Hoikas]

Cope with some rename changes.

[Jrius]

Sorry for being late to the party, but maybe this could tie into material.game_settings.use_backface_culling ? (Either keep both in sync, or rely on it instead of a new property.)
Note that theoretically, material.game_settings.use_backface_culling is specific to the Blender Game renderer (and the relevant UI toggle is hidden if you select another renderer). The reason I'm mentioning it is that it DOES make the material two-sided in the textured view for the Blender Internal/Korman renderers.

[Hoikas]

That sounds like a good idea, but isn't BGE gone in Blender 2.80 and above?

[Deledrius]

That sounds like a good idea, but isn't BGE gone in Blender 2.80 and above?

One way or another, that's irrelevant for Korman, I assume.

[Jrius]

Blender 2.80 moved the use_backface_culling property directly into the material class, but it still works the same.

[Hoikas]

Will 2.80 migrate the old BGE property into the materials for us? I'd like to future proof this as much as possible now so that there are no surprises an unknown amount of time in the future.

[Jrius]

Unfortunately it's not migrated. Good catch.
Furthermore, all materials created in 2.80 are now two-sided by default (probably because unlike Eevee, Cycles is unable to do backface culling), which means pretty much everyone will forget to reenable that checkbox at some point when creating stuff in 2.80, which is bad practice.
So I guess it's better to have our own dedicated property, which will correctly migrate when upgrading and have a sane default value for new materials. If we can still sync use_backface_culling to our property for better viewport display, all the better, but it's not a huge priority.

...With that said, Blender 2.80 wipes clean materials from 2.79 anyway (save for custom props). So upgrading older files will require a custom operator/utility to convert existing materials to the equivalent Korman will use in 2.80.