1. A method, executable in a computer graphics system comprising a computer and a display element, the display element being operable to display a human-perceptible image in response to a display-controlling electrical output from the computer, the computer being operable to generate the display-controlling electrical output based on calculations of pixel values for pixels in the image, respective pixel values being representative of at least one point in a scene as recorded on an image plane of a simulated camera, the computer being operable to generate pixel values for an image using a ray-tracing methodology, the ray-tracing methodology comprising the simulating of at least one ray shot from the pixel into a scene, or from the scene to a pixel, along a selected direction, the ray-tracing methodology further comprising the calculating of the intersections of rays and surfaces of objects in the scene and the simulating of trajectories of rays illuminating objects in the scene, the method comprising: employing shallow bounding volume hierarchies (BVH) to enable rapid tracing of incoherent rays using streaming SIMD (Single Instruction, Multiple Data) instructions; and accelerating ray tracing by using acceleration data structures with high arity to enable processing of nodes using streaming SIMD instructions with reduced memory requirements, wherein high arity data structures are generated by merging levels of the bounding volume hierarchies; the merging of levels comprising tree construction by flattening a binary tree, wherein flattening a binary tree comprises collapsing a binary tree by keeping each k-th level of a given tree, and discarding intermediate levels; wherein the SIMD instructions are used in construction of bounding volume hierarchies, tree traversal and leaf intersection; wherein the use of streaming SIMD instructions is enabled by increasing the arity of acceleration structures; and further comprising: utilizing caching to accelerate processing of shadow rays in a global illumination process without increasing memory requirements; utilizing per-ray ordered, sorted traversal; and applying streaming SIMD instruction processing to leaf intersection, using a cache storing image-related triangles in SIMD-compatible form.