search

buildingSMART / IFC4.3.x-development

Repository to collect updates to the IFC4.3 Specification
Other
158 stars 81 forks source link

How to represent multiple materials in a layer? #469

Open Moult opened 2 years ago

Moult commented 2 years ago

I'm setting up project libraries and wondering how are multiple materials in a layer represented? E.g. in a wall commonly insulation and framing will occur in the same layer.

aothms commented 2 years ago

I think inother issue we also discussed this. This is one of my reasons to propose to deprecate MLS altogether.

My proposal. Nesting (ordered decomp) means layers. Aggregation (unordered decomp) means parts. That way you could easily come up with a composite decomposition structure:

  1. Layer0: Brick
  2. Layer1:
    • Part0: Insulation
    • Part1: Frame
  3. Layer2: Brick
Moult commented 2 years ago

The issue is that for the most part MLS matches how architects and wall manufacturers design and specify things. They don't bother with the details of every single stud or junction, just a general "here's the layers". If aggregation means that each wall object would be multiplied by N objects for N layers, I don't think that's a good fit for the designer's mindset.

aothms commented 2 years ago

Well, yes, but it should be seen in conjunction with more intelligent behaviour on type objects, so that aggregates types can be instantiated.

Some BIM exporters already default to exporting layers as decompositions and most viewers consider the aggregated object as the first point of contact with the end-user. So I don't think there is a real difference.