[BEM, Topologic] BIM Energy Modeling
Starting a new dedicated topic following our discussions :
quotes from Safely split an IFC
@Cyril I just realised you mentioned energy model. I have a very hastily written half-baked completely incomplete Blender->gbXML exporter code here. Maybe it is useful to you. Maybe you can help write a fully featured one? You no doubt have much more experience in energy models and I have zero experience :)
Once we have a reliable gbXML workflow (by the way, gbXML spaces have an attribute that relate back to IFC spaces), that would be a huge benefit as people can then use Blender as an authoring tool for energy models.
@Moult I think I could use your gbXML exporter quite easily in FreeCAD... Would you be interested in trying to make it Blender-independent? I'm thinking in FreeCAD it could be fed with a list of Arch Space objects. There is quite a lot that is geometry-dependant, but maybe we could isolate that as much as possible into separate methods, then in FreeCAD I can derive a new class from yours and reimplement the geometry-related functions
@yorik Sure thing :) I haven't touched the code in a while and it currently is quite low on the to-do list, but gbXML expects a closed mesh polygon to represent a space (and from memory, only supports that, not like IFC which has 200 options :) ). Each face of the polygon represents a "surface". This is very simple in Blender and is isolated to the
create_spacefunction. As spaces are almost always very simple boxes / box-like closed shapes, this should also be very simple in FreeCAD :) Feel free to use it and please let us know when you do :)
Note on gbXML vs IFC (IfcRelSpaceBoundary)
IfcRelSpaceBoundaries have some advantages over gbXML. See also specialized IfcRelSpaceBoundary2ndLevel. gbXML is kind of the old way supported by almost any energy analysis software. Geometric generation process is almost the same for gbXML and IfcRelSpaceBoundaries. Adapt to local standard is hard with gbXML as it contains limited building information.
Current personnal progress
I am currently working on the other part of the process which is :
- Read an Ifc which contains IfcRelSpaceBoundary exported from any software (eg. Revit, ArchiCAD currently)
- Adapt or generate geometries for local standards. (which could become IfcRelSpaceBoundary level n in future according to discussions on building smart forum)
- Output information in simple and consistent manner for use in the energy analysis software
I'll give more detail soon.
I will be happy to work on gbXML/IfcRelSpaceBoundary generation as a team because I am not a geometry or algorithm master so I will need some help to avoid spending decades on this or get awful performances.
- I know that there is already energy analysis tools in Blender but I don't know how it works and if it is able to generate gbXML already. Cf. An Arch project showcase on FreeCAD forum
- I know that LadyBug Tools already have tools related to gbXML and energy analysis. Investigate a little here is required to avoid reinventing wheel.
- There is many scientific publication related to IfcRelSpaceBoundaries generation. I will post links on wiki for the ones publicly readable on web.