A graphics system configured to operate on a collection of vertices to determine mappings from an initial order to secondary and tertiary ordering. The initial order corresponds to the ordering of the vertices in an input buffer. The secondary (tertiary) ordering corresponds to the ordering of the vertices along a triangle major (minor) axis. The graphics system computes horizontal and vertical displacements along edges of the triangle in the initial ordering, and uses the signs of the horizontal displacements and vertical displacements to access a mapping table which determines the mappings. The mappings may be used to rasterize the triangle in terms of pixels (or samples).