Alien Roller Coaster

I continue to explore tubular organic shapes with freely moving balls inside. This time I used a CAD program (Cheetah3D) to create a closed spline shape and then swept it with a circle. This way I created an organic shape with a constant diameter. I then opened this shape in ZBrush and used it as the basis for the design. Essentially this swept spline becomes the inside of the tube in the final design. Because it was created with a constant diameter circle, the balls will roll freely inside. Se