Intersection testing in a ray tracing system using convex polygon edge signed parameters

Abstract

A method and an intersection testing module in a ray tracing system for performing intersection testing for a ray with respect to a plurality of convex polygons, each of which is defined by an ordered set of vertices. The vertices of the convex polygons are projected onto a pair of axes orthogonal to the ray direction. For each edge of a convex polygon defined by two of the projected vertices, a signed parameter is determined, wherein the sign of the signed parameter is indicative of which side of the edge the ray passes on. If the ray is determined to intersect a point on the edge then the sign of the signed parameter is determined using a module which is configured to: take as inputs, indications which classify each of p, q, pand qcoordinates as negative, zero or positive, and output, for valid combinations of classifications of the p, q, pand qcoordinates, an indication of the sign of the signed parameter. It is then determined whether the ray intersects the convex polygon based on the signs of the signed parameters determined for the edges of the convex polygon.