A method for forming a retroreflective prism in a substrate includes inserting and retracting a single point diamond tool through a surface of the substrate while moving the single point diamond tool, the substrate, or both the single point diamond tool and the substrate in a direction of travel along at least one axis to generate a facet in the substrate having a facet face parallel to the direction of travel of at least one of the single diamond point tool or the substrate. The facet face has an angle defined by a chiseling edge of the single point diamond tool. The inserting and retracting is repeated at a plurality of locations on the substrate to form an array of retroreflective microstructures on the surface of the substrate. At least one of the array of retroreflective microstructures is a retroreflective prism having a polygonal projected aperture.