The deal is simple: i need a hole in the model. I mask two sides of an object, hide and delete hidden, at this point the model is still the same (if i export it and import in my 3D software, it’s pixel to pixel correct, except the hole obviously), as soon as i use CurveBridge tool and close the gap with the new geometry, after exporting the model to .obj and importing it in my 3D software, the model becomes 4-5 times bigger the original and the origin point is moved all of the sudden. How can i fix that?
Hi @madmorze!
Please open the Tool> Export menu at the time of the Curve Bridge mesh creation. Watch the Scale slider there when you complete the bridge. Does the value change? If so, from what to what?
Any value shift there could potentially change the export scale of your mesh. In that case you could theoretically restore it by noting the exact value in the slider before the shift and restoring that exact value after.
I’m interested to know what you find.
Thank you! 
Oh thank you, that should probably fix it for me. As soon as i use CurveBridge tool, it automaticly sets a scale to 1 and everything else to 0. So if i bring back the original values, it should work fine!
Yesterday i went even further and tried other formats thinking that the export process is an issue here and found out that .fbx for example does the reverse with my model: it scales it down 4-5 times from the original
I quick update:
Although manually entering the export data back help’s a bit, it still doesn’t export the model in a pixel correct manner. I assume this is because somewhere down the line there are more than 5 numbers after the decimal and so the final model comes out just a bit differently from the original.
At this point i’m gonna assume that there’s nothing we cand do about it until some sort of an update in the future.
The issue with Curve Bridge looks like a bug to me. I’ve forwarded this to the Development team for attention.
In your other situations I might suspect a problem with your import procedure. ZBrush’s effective worldspace is finite. Meshes that are drastically oversized or off-center are going to experience problems in the program.
For this reason when you manually import a mesh with the import function AND there are zero values in the Tool> Export menu it unifies the mesh (scaled to XYZ of approximately 2 and centered in the worldspace.) It records the values needed to restore the mesh at export to the exact same original size and offset in that menu. Any change to these values may result in a scale shift when working between programs.
But those values are specific to that Tool and no other. Where problems arise is when a user imports a mesh while a tool that already has non-zero values in that menu is active. In this case the incoming mesh will inherit those values, even though they are not meant for that tool. The values required to restore one mesh to its original size do not apply to a different mesh. So what can happen is that a mesh may end up looking about the same size and centered in ZBrush even though it is being scaled differently at each export.
It’s for this reason we recommend switching to the default polymesh 3d star primitive mesh in the Tool palette to use as an import target before importing any mesh. This is solely because that tool has zero-ed out values in that menu and you can be assured of a clean slate.