Need advice to unwrap T-spline box from Inventor



I create T-spline box in Inventor, like below:

Then I try export stp file and obj file.

I import to 3ds max. this model look like stool.

I hope to make smooth surface with fabric material. currently they discontinue.

Need avice to unwrap better.

attached file: (115.5 KB)


my rule for UV is to do it on a low density mesh