1. A method of intersection testing for ray tracing, comprising: receiving, in an intersection testing resource, ray data defining a ray; receiving, in the intersection testing resource, geometric shape data including 3-D positional information for the shape represented by block floating point format data comprising a plurality of significands sharing a common exponent; testing the ray for intersection with the geometric shape based on the received ray data and the geometric shape data; and outputting an intersection result in response to the testing indicating a possible intersection of the ray with the geometric shape.