Here’s a screenshot of the difference between an RC’s OBJ and FBX file when importing to Zbrush.
You can see that the imported OBJ file looks weird and probably has an issue on the orientation, but that’s actually the correct orientation. That’s what RC’s orientation is (X-axis) while Zbrush and most other 3D programs are using Y-axis by default. But the real problem is, why does the FBX file has a different orientation with an OBJ file?? Shouldn’t be the same? What’s the reasoning behind this?
Now, there’s an FBXExportImport plugin in Zbrush where you can supposedly “change” the up-axis of the model. Well, it doesn’t work. I’ve tried all the options and combinations, but same result. The plugin doesn’t help at all.