The basic unit of this model is an octahedron made from a single sheet of "silver rectangle" shape that I created five years ago. In 2017 I had the idea to use the octahedron model to achieve this fractal after being inspired by a photograph of a similar model by Dave Mitchell I saw on the internet.
Strictly speaking, the Sierpinski 3D fractal is not a modular origami model, because the octahedra are not joined together but simply sit on top of each other. The octahedra are then arranged and placed side by side in a pyramidal shape (Tetrahedron), halving the format of the starting sheet gradually and then the edge of the octahedron. The result is a nice fractal of Sierpinski 3D. Depending on the number of octahedra of different dimensions used, the name is identified with level 1, level 2, level 3, etc.