A method of generating an image. The method includes simulating a presence of at least one light source within a virtualized three dimensional space. Within the virtualized three dimensional space, a light sensing plane is defined. The light sensing plane includes a matrix of a number of pixels to be displayed on a display screen. The method further includes using a light transport procedure, computing a gradient value for each pixel of the matrix to produce a number of gradient values. The gradient computation involves selecting a plurality of light path pairs that contribute to a pixel wherein the selection is biased towards selection of more light paths that pass through pixels having larger gradient values. The plurality of gradient values are converted to a plurality of light intensity values which represent the image.