Rendering Algorithms

A new hierarchical grid acceleration algorithm was introduced that allows much better control than the old static grid accelerator in mental ray 2.1.
Multipass rendering and merging is now supported. Render passes are independent renders of portions of the same scene, each generating a subsample-based layer file. Layer files can be merged back when rendering the last pass, or all layers can be merged as a separate process. Merging can be done in custom merging functions. Multipass rendering was introduced in mental ray 3.1.1, and was significantly enhanced (using an incompatible syntax extension) in mental ray 3.1.2.
The -nomaster command-line option and the mi_job_set_slaves_only function call allow excluding the master from all tasks that can be handled on slaves, such as rendering and tessellating.
The bsp shadow on option enables the new shadow BSP tree, which holds all shadow objects. The main BSP tree then only holds trace objects. This is useful if the scene contains simplified shadow stand-in geometry and has very low shadow ray coherence, for example if a light dome computed from a chrome dome photograph is used.
The new multipass rendering facilities allow rendering a scene in passes, and combining the results on a subpixel level.
Objects may specify min and max sampling parameters that constrain the sampling range in the options. For eye rays that do not see any objects, the samples statement in the options block allows an optional default constraint.