1. A method comprising: receiving a plurality of objects from a 3-D virtual scene, wherein the plurality of objects is arranged in a hierarchy; generating a plurality of identifiers for the plurality of objects, wherein the plurality of identifiers comprises a first identifier for a first object in the plurality of objects, wherein the identifier is generated based on a position of the first object in the hierarchy; performing a rendering operation on the plurality of objects to generate a deep image, wherein the deep image comprises a plurality of samples that correspond to the first object; and propagating the plurality of identifiers through the rendering operation such that each of the plurality of samples in the deep image that correspond to the first object are associated with the identifier.