Scene model data, including a scene geometry model and a plurality of pixel data describing objects arranged in a scene, is received. A primary pixel color and a primary ray are generated based on a selected first pixel data. If the primary ray intersects an object in the scene, an intersection point is determined. A surface normal is determined based on the object intersected and the intersection point. The primary pixel color is modified based on a primary hit color, determined based on the intersection point. A plurality of ambient occlusion (AO) rays each having a direction, D, are generated based on the intersection point, P and the surface normal. Each AO ray direction is reversed and the AO ray origin is set to a point outside the scene. An AO ray that does not intersect an object before reaching the intersection point is included in ambient occlusion calculations. The primary pixel color is shaded based on the ambient occlusion and the primary hit color and an image is generated based on the primary pixel color for the pixel data.