Antipodal points are two points on the opposite sides of a shape. Points are antipodal, if two lines drawn parallel to each other, each going through one point, enclose the entire shape. In 3D spaces parallel planes are used instead of lines.

With circles and spheres, any two exactly opposite points are antipodal. However, corner points of polygons may have one, multiple, or no antipodal partners depending on the polygon shape and the rules set out above. Note that only the corner points, not the edges of a polygon are taken into account.