This is a nautilus shell split in half.I have included two .stl's, one is 1 mm thick walls and the other is 1.5 mm thick walls.I liked the 1 mm thick version but it did not print well on my cupcake with an MK5, maybe those with newer printers can print it cleanly.The 1.5 mm thick version is shown in the top photo & last photo and printed much better on my setup.The 1.5 mm thick version will likely print better than the 1.0 mm if you have a cupcake with an MK4 printer.the .mac files create the geometry in ANSYS.the 1 mm .stl has the configuration of internal walls like nycdesigner printed as shown is the 2nd picture from the top.The 1.5 mm .stl has the configuration of the internal walls as shown in the picture shown 2nd from the bottom. The shift was made so that the walls would not be too close together in the smaller cells.