1. A method for interfacing with computer executable shader code, comprising: accepting, through a ray emit call, definition data for a parent ray and an association of the parent ray to a pixel of a 2-D image to be rendered from a 3-D scene composed of objects; selecting a shader selected based on an intersection testing result for the parent ray; accepting one or more child rays from the selected shader through the ray emit call during execution; continuing the pixel association with each of the child rays; selecting one or more shaders based on intersection testing results obtained for at least some of the child rays; and accepting contribution(s) directly into a buffer for the pixel, through a contribute call, from one or more of the shaders selected for the child rays during execution.