Importing an IGES file via the Okino IGES importer appears to have lots of square planes in it. Why?
You need to export your IGES file as a surfaced model (128/144/142 entities) with uv-space trim curves. If you import the model, press F2 on the keyboard and scroll backwards in the message window then you may find that your IGES file has no uv-space trim curves defined in it. Alternatively, import via the PTC Granite IGES importer.