When the vertex coordinates are too large, there will be accuracy problems

[laizilianglaiziliang]

When the vertex coordinates are too large, there will be accuracy problems.
You can see a picture that the stairs are broken due to insufficient accuracy when using IfcSplitAndMerge, while the other image is good when using other software.

[ifcquery]

That can be solved with a transform matrix. High coordinate values go into the matrix. Coordinates are multiplied with inverse matrix, so that they have small values.
Can you share the IFC file for testing? One or two parts are enough. You can select& write file with IfcSplitAndMerge

[laizilianglaiziliang]

thx your answer. ql78.zip contains my IFC file,you download and upzip it.
ql78.zip

[ifcquery]

It seems to work in the latest version:

[laizilianglaiziliang]

Great. Want to know more about whether the simpleviewerexampleqt project can also be displayed normally?

[ifcquery]

This is a different project. simpleviewerexampleqt is https://github.com/ifcquery/ifcplusplus (open source)

IfcSplitAndMerge is https://github.com/ifcquery/ifcsplitandmerge (not open source)

They have completely different code.