1. A method, executable in a computer processor element, the processor element being operable to generate pixel values for an image using a ray-tracing methodology comprising calculating intersections of rays and surfaces of objects in the image, the method comprising: (A) computing, in the processor element, a minimal axis-aligned bounding box of an intersection of a given axis-aligned bounding box B and a triangle under linear motion, the motion of the triangle having associated motion vectors 
 {right arrow over ( V i s V i e )}, by: (1) using the processor element, initializing a bounding box B I as empty; and (2) using the processor element, executing an intersection process that intersects edges of the triangle at times t s and t e and the triangle's motion vectors 
 {right arrow over ( V i s V i e )} with slabs S x , S y , and S z whose intersection is the given axis-aligned bounding box B, and extending bounding box B I by intersection points resulting from the intersection process until the minimal axis-aligned bounding box is computed, wherein t s is a start time and t e is an end time, and wherein V i s is a vertex of the triangle at time t s and V i e is a vertex of the triangle at time t e ; and (B) traversing, in the processor element, a ray tracing acceleration hierarchy for a given set of rays, the traversing comprising computing decisions for a representative form of the rays, without requiring a traversing of all rays in turn.