message: Document the regions and ghostregions of mpi distrib device model
diff: @@ -171,3 +171,39 @@ the application can create a communicator with one rank per-node to then
  run OSPRay on one process per-node. The remaining ranks on each node
  can then aggregate their data to the OSPRay process for rendering.
  +There are also two optional parameters available on the OSPModel created
  +using the distributed device, which can be set to tell OSPRay about your
  +application's data distribution.
  +
  + ---------- ----------------- ----------------------------------------------
  + Type Name Description
  + ---------- ----------------- ----------------------------------------------
  + `box3f[]` regions [data] array of boxes which bound the data owned by
  + the current rank, used for sort-last compositing.
  + The global set of regions specified by all ranks
  + must be disjoint for correct compositing.
  +
  + `box3f[]` ghostRegions Optional [data] array of boxes which bound the ghost data on
  + each rank. Using these shared data between nodes
  + can be used for computing secondary ray effects
  + such as ambient occlusion. If specifying ghostRegions,
  + there should be one ghostRegion for each region.
  + ------ ------------ -------------------------------------------------------
  + : Parameters for the distributed OSPModel
  +
  +See the distributed device examples in the MPI module for examples.
  +
  +The renderer supported when using the distributed device is the `mpi_raycast` renderer.
  +This renderer is an experimental renderer and currently only supports ambient occlusion
  +(on the local data only). To compute correct ambient occlusion across the distributed
  +data the application is responsible for replicating ghost data and specifying the
  +ghostRegions and regions as described above.
  +
  + ---------- ----------------- -------- -------------------------------------
  + Type Name Default Description
  + ---------- ----------------- -------- -------------------------------------
  + int aoSamples 0 number of rays per sample to compute
  + ambient occlusion
  + ------ ------------ -------------------------------------------------------
  + : Parameters for the distributed OSPModel
  +
  