Feature suggestion: Support multiple meshes per element

[xeolabs]

Would it be possible to allow an element to use multiple meshes, as a feature in a future schema version? This would enhance geometry reuse in combination with #38, allowing primitive shapes to be reused as parts of different elements.

[paireks]

I haven't found a reason before to support multiple meshes, cause even if element is constructed with multiple meshes, I could always join them first. But please let me know it there are some scenarios where you still need separated meshes for single element. Such modification would probably break existing user space, therefore probably it could be considered only for 2.0.0 version or later.

[xeolabs]

I haven't found a reason before to support multiple meshes, cause even if element is constructed with multiple meshes, I could always join them first. But please let me know it there are some scenarios where you still need separated meshes for single element. Such modification would probably break existing user space, therefore probably it could be considered only for 2.0.0 version or later.

Cool - only reason would be a work with authoring software that composes an element from multiple 3D primitives, where some or all of those meshes are shared among other elements. It would avoid needing to join primitives together and create more meshes, for the case when two or more elements share a different subset of the primitives. Also for memory efficiency.

For example, consider some authoring software that has a box, sphere and cone mesh. One element uses the box, and a second element uses the box, sphere and cone. If an element can have multiple meshes, then these two can just share the unmodified meshes in the .bim output. If we're restricted to one mesh per element, then the second element needs to make a mesh in the .bim that is the combined box, sphere and cone.