Advanced Micro Devices, Inc.
WATER TIGHT RAY TRIANGLE INTERSECTION WITHOUT RESORTING TO DOUBLE PRECISION

Abstract:

Described herein is a technique for performing ray-triangle intersection test in a manner that produces watertight results. The technique involves translating the coordinates of the triangle such that the origin is at the origin of the ray. The technique involves projecting the coordinate system into the viewspace of the ray. The technique then involves calculating barycentric coordinates and interpolating the barycentric coordinates to get a time of intersect. The signs of the barycentric coordinates indicate whether a hit occurs. The above calculations are performed with a non-directed floating point rounding mode to provide watertightness. A non-directed rounding mode is one in which the mantissa of a rounded number is rounded in a manner that is not dependent on the sign of the number.