Relocating / positioning an IFC file in Bonsai 0.8.1

E by ejs on 3 Mar 2025, edited 4 Mar 2025 #

Hi folks,

Prior to Bonsai 0.8, repositioning an IFC file was quite easy. Now, I miss something trivial.

I have some IFC models in IFC2x3, produced mainly in Revit, and I need to align them with the IFC4 file from Civil3D, which exposes the right coordinates. I have the transposition numbers from Trimble Connect, but I can't find the proper way to apply them. The only place I can alter values is the 'True North' Section. Entering values into the 'Georeferencing Calculator' will set both the 'Local' and 'Map' points to the same values. I think, I need my 'Local coordinates' of the IFC file to be set to the 'Project Origin' coordinates, which should be equal to setting


IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,0.01,#18,#19);

#10= IFCCARTESIANPOINT((0.,0.,0.));

#14= IFCDIRECTION((1.,0.,0.));

#16= IFCDIRECTION((0.,0.,1.));

#18= IFCAXIS2PLACEMENT3D(#10,#16,#14);

to the required coordinates, eg. #10= IFCCARTESIANPOINT((6063318057.0, 584013164.0, 101200.0)); . But maybe I'm digging in the wrong place?

Re-exporting the IFC files is not an option.

S by steverugi on 3 Mar 2025 #

@ejs please see if also this thread might be of help

E by ejs on 3 Mar 2025, edited 4 Mar 2025 #

@Massimo said:

@ejs have you read this?

https://docs.bonsaibim.org/guides/authoring/georeferencing.html

Sure. And no meaningful results for two hours. I'm trying to keep on IFC2x3 right now, but even when converted to IFC4 its not working as I expect.

For now, I've separated origin point for IFCSITE and IFCBUILDING into a separate point, and left origin points for the other elements in the 0,0,0 or the original positions.

~~Testing time now. Need to introduce TrueNorth Rotation :)~~

And that actually worked. The third parameter in IFCAXIS2PLACEMENT3D() is the unit vectors projections to X and Y axes, and may be defined by IFCDIRECTION(). So, add the required base point and rotation to the end of IFC file, find the IFCSITE definition and hack its reference point.

M by Moult on 4 Mar 2025 # +1 votes

I highly, highly recommend not manually editing the IFC SPF file to change coordinates. Instead, use the SetFalseOrigin recipe in the IfcPatch panel: https://docs.ifcopenshell.org/autoapi/ifcpatch/recipes/SetFalseOrigin/index.html