I am inputting multiple contours into a vtkAppendPolyData object, does it matter what order I add these contours? I want to create a convex hull. Say from left to right, I create a large circle, small circle, and large circle. I would like to form a convex hull that looks like a hourglass. I tried using vtkDelaunay3D to render it, but I ended up getting a hull that looks like a cylinder.

Any help would be appreciated. Thanks!

This is impossible because convex hull of an hourglass shape is a cylinder. You might be able to reconstruct hourglass shape from points using vrkDelaunay3D using non-zero alpha parameter or using other methods described in this post: