Configurable Materials

[Qwlouse]

Currently material information is tied to the object and stored as an .mtl file along the .obj file for the visual geometry. This is not ideal for two reasons:

• .mtl is very limited and cannot store PBR based attributes such as metalness
• there is currently no way to change/randomize the material of objects

We should add:

• A way to store and import materials separately from objects. Maybe the asset source could create Materials the same way it creates objects.
• A way to configure a few basic material properties, at least including color, roughness, specularity, and metalness.
• A way to change textures. Possibly as part of materials?
• export material information as ground truth information
• Possibly assign physical properties to materials such as friction, density and bounciness.

[Qwlouse]

There is some support for this since #51 and #54. Kubric now has a concept of materials that can be added to certain objects. But the supported materials are very limited, and there is no automated support at the asset source level.