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Mesh color to IFC export in Blender
Maybe I'm posting this miles away from where I should, but I was lured here by blenderbim.org/community so here goes.
Using the Blender BIM add-on, is there a way to include vertex color in an IFC export? As a construction surveyor, I produce point clouds by laser scanning and drone photogrametry. These can be converted to meshes, imported in Blender and then exported to IFC. Retaining mesh color would greatly help interpreting these files.
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@Joel colours assigned to faces are certainly retained in the BlenderBIM Add-on. However IFC does not yet support vertex colours in its current form - a future proposed extension for point clouds will allow for this, but right now, you're out of luck. However, in the past, people have written scripts to convert points to planes or cubes which then have the appropriate colour, but those are usually OK for a small surveying sample, not something as dense as a point cloud.
For the moment, I'd recommend keeping point cloud data and IFC data separate. Hope it helps.
Hm. Yeah, I suspected there would be problem retaining colors in the IFC export. It is almost as if the designers of IFC back in the 1990s didn't have massive surveying data in the form of point clouds or meshes in mind ... ;)
Converting a point cloud to a mesh is relatively simple. To keep file sizes reasonable, large clouds over entire buildings must be made into really simplified meshes. But those can still have their uses. It would be even better if the color of the mesh were retained in the IFC. Could the mesh be broken down so each individual face becomes an IFC object? Hm.
Well I guess the idea was that IFC is a "BIM" format-supposed to store rather primitive geometrically defined "intelligent" building elements, rather than "dumb" point clouds, but admittedly having the original surveyors data for example as a ifcBuilding representation could have its value.
@Joel point clouds are supported, and there is an extension that allows full colour and I suspect other data to be associated, as well as to associate point cloud subsets as geometry to BIM elements. However, this is just a proposed extension, and IFC has really been held back by the glacial speed of implementers... so, yeah. Ping @aothms who is the expert on this who wrote academic papers on the topic, who might be able to advise you better on what's possible here and now.
For meshes with vertex colours they added the triangulated faceset and color map https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/schema/ifcpresentationappearanceresource/lexical/ifcindexedcolourmap.htm but I don't think it's really implemented in software either.
Re point cloud extensions, I still think it makes sense but it depends on your use case. If you need long term archiving with rapid access and deep semantic links it makes a lot of sense to store everything in an efficient indexed container with programmatic access. If you need to use conventional software you're probably better off keeping the files separate in their normal formats.