1. A method, comprising: creating a spatial index having nodes representing bounding volumes in a three dimensional scene, comprising: a) drawing an initial splitting plane within a bounding volume at a first point along a reference axis; b) determining a number of primitives intersected by the initial splitting plane; and c) jittering the splitting plane along the reference axis and by operation of one or more computer processors to determine a location for the splitting plane where fewer primitives are intersected; wherein jittering the splitting plane comprises: selecting a second point a first distance from the first point along the reference axis, wherein the second point is oriented in a first direction along the reference axis with respect to the first point, and wherein selecting the second point comprises: determining if a group of vertices are close to the first point in the first direction; and if so, selecting the second point to be a distance from the first point beyond the group of vertices in the first direction; drawing a second splitting plane within the bounding volume at the second point; and determining a number of primitives intersected by the second splitting plane.