IFC relationships has anyone had any joy?


#1

I have created a simple model with walls and windows and assigned them to IfcWall and IfcWindow respectively. The IFC file which I get on Export, doesn’t have any relationship between the IFCWALL and the IFCWINDOW, i.e, the wall should have an association to an opening void and a relationship established that a window fills the void. The things(properties) I wanna see in my IFC file, that are not currently present, are IFCMAPPEDITEM, IFCMAPPEDREPRESENTATION, IFCRELVOIDSELEMENT, IFCRELFILLSELEMENT, IFCWINDOWSTYLE etc.

So, when I view my IFC file in a tree view, there should be a hierarchy where the IfcWall has IfcWindow as a sub-node (like a parent-child relationship).

Also, to make the IFC file shorter, multiple walls should be consistent and be ordered as a group of the same product and the IfcWindowStyle should be associated to windows with common definitions.

I am using the default IFC2X3.xsd as my classification.

Has someone cracked a way to achieve this with Sketchup Export? Thanks.


#2

With native export, there are still some flaws:


#3

Thanks Mike, I have bene bashing my head against the wall, I figured I was doing someting wrong. I will check out the link an dgive it a try. B)


#4

Hey Mike the IFC export from this plugin didn’t give us the desired result and the required properties are still missing, are you getting a similar result? It appears to be a clear oversight in the export or am I missing something?
However, values in Name, Description and ObjectType, get correctly written to the IfcWindow in the ifc file. Why can’t I write to the OverallHeight and the OverallWidth?


#5

Are you checking with another IFC viewer like Solibri?

If you use the plugin, you don’t have to input the measurements manually, btw.

Then, you can see the difference between the export from SketchUp:

and via the plugin:

The import of IFC in SketchUp seems to have issues as well…


#6

“Normally” the OverallHeight and OverallWidth parameter is filled by the CAD software itself based on the geometry.

If you use the IFC Manager extension, this value is exported as indicated by @MikeWayzovski.
With this extension a correct IFC (2x3) export can be generated.
This extension follows the IFC scheme in accordance with buildingSMART.

The standard IFC import and export function of SketchUp Pro does not yet work correctly in accordance with the buildingSMART IFC requirements. It is very important that SketchUp improves the native IFC import and export in upcoming versions or updates.


#7

Hi Andrew!
In the IFC-manager extension I have tried to fix as many of the problems in the native export as possible.
You should be able to manually fill the fields shown in the dynamic component options window, but only manual for now.
I have not yet found a way to automatically fill them (for ‘normal’ SketchUp components) without a lot of (error-prone) guess-work. The only geometric things you can be sure of are the bounding box and volume, as far as I know.
A lot more can be achieved using dynamic components, but even then relations (apart from the component hiërarchy used for the project structure) are very difficult. You could create a relation based on a ifcwindow glued on a face inside a ifcwall. But how do you detect a hole in the wall, and make sure that this hole is the right one for the window closest to it? I think the best way to solve this is by specific drawing tools like an improved version of my ‘bim-tools’ or your own! :smiley: Maybe we should talk about some common ‘rules’ for detecting these relations!
Import indeed has it’s own problems, as mentioned by Mike, so testing the export using a round-trip back into SketchUp is not the best test of the created IFC.
Mapped items by the way are easy, and are on my to-do list :wink:
Cheers!
Jan Brouwer


#8

Hi Mike thanks for the response mate, we have been using Rhino to cross-check imports yet the window size is the issue every way we turn, it is not being written to the IFC file itself so no program can import it unfortunately.

IFCWINDOW(‘0NUEEOoBn78h1$J42iIpUZ’, #2, ‘’, ‘Description of Object’, $, #48, #53, $, $, $);


#9

Thanks Brewsky, I will flick you an email. B)


#10

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