This feature pre-calculates the shadows and lighting from a user defined Maya feature called "final gather". This pre-calculation takes place on multiple render servers across a selected frame range (for example, every tenth frame of the sequence), and is merged into a single fg_map. After this pre-calculation is complete, the main render job is started, and each render server will load this fg_map to render the final image more efficiently, without having to re-calculate the final gather points.

This feature is designed to work only for scenes that have static lighting and geometry. The only object in the scene that is animated is the camera. If lights, geometry, or any other scenes objects that affect the rendered lighting move, this feature should NOT be used.

Known Issues:

Currently this feature is designed to pre-calculate the final gather points based on the DEFAULT scene layer. What this means is that final gather map is calculated based on the objects and lights as they are at the moment the scene file is opened, as opposed to the state of the shot on a particular render layer.

So, for example, if this feature is used to calculate the final gather lights and shadows from the default objects and lights, and then it continues to render multiple render-layers where various objects are invisible, the shadows will be on the surfaces adjacent to the objects that were previously visible when the final gather maps were generated.

In the future, this feature may be upgraded to generate UNIQUE final gather maps on a per render layer basis.

So, for the time being, users who want to take advantage of this feature should know that the final gather maps are generated based on the default state (for example: visibility, etc) of all objects, geometry and lights, regardless of which ever render layers are to be subsequently rendered.