1. A method comprising: receiving a plurality of objects from a pre-rendering process of a 3-D virtual scene, wherein the plurality of objects is arranged in a scene-graph 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 scene-graph 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 and with a rendered color; exporting the scene-graph hierarchy from the pre-rendering process to a post-rendering process; receiving a selection of the first object from the scene-graph hierarchy in the post-rendering process; selecting the plurality of samples that correspond to the first object from the deep image by identifying samples in the deep image that are associated with the first identifier; and performing a post-render operation on the plurality of samples in the deep image that correspond to the first object.