How to make a fractal-top prism

[FudgeFlakeNut]

   

How would one make a prism with the top and bottom faces a 2D fractal such as the Dragon, Sierpinski Triangle or Terdragon? I am making something that uses a combination of prisms in those shapes.

[Garth Thornton]

It depends on the fractal. For a shape with no filled interior, such as the Sierpinski triangle, you can do it in XD with extrusion.
Starting with the Sierpinski, add a holon, set all scales to 100, click the Free Holon and Hide Parent Shape buttons, and use the Extrudez metamorph in Local, adjusting Amount for the height.
If you have a fractal shape that already fills in the spaces solidly, that should work too, though it could be slow as it will get a solid prism, not a hollow one.
If the shape is empty in the interior, you can extrude the outline but I don't know any direct way to get flat top and bottom. If you instead add one or more prisms to be iterated you may be able to fill the shape but not with constant height.

[Garth Thornton]

XD currently allows Extrudez to make a triangular prism. I'm experimenting with future options. The limitation is that the method of closing the top converges towards the center, which is only clean for concave shapes. Otherwise you get extra flat areas outside the shape. Here is an example viewed from underneath.