but a lower symmetry [2,2,2], order 16, possibly doubled to 32 if the two rectangles are identical. Coordinates The coordinates of a p-q duopyramid (on a unit 3-sphere) can be given as: All pairs of vertices are connected by edges. Perspective projections Orthogonal projections The 2n vertices of a n-n duopyramid'' can be orthogonally projected into two regular n-gons with edges between all vertices of each n-gon. The regular 16-cell can be seen as a 4-4 duopyramid, being dual to the 4-4 duoprism, which is the tesseract. As a 4-4 duopyramid, the 16-cell's symmetry is [4,2,4], order 64, and doubled to , order 128 with the 2 central squares interchangeable. The regular 16-cell has a higher symmetry [3,3,4], order 384. Example 6-4 duopyramid References 4-polytopes