message: Add some comments, use the clipbox param to clip
  though the example doesn't create any spheres crossing the boundary that
  need to be clipped anyways.
diff: #define RUN_LOCAL 0
  -namespace ospRandSphereTest {
  +/* This app demonstrates how to write a distributed scivis style
  + * renderer using the distributed MPI device. Note that because
  + * OSPRay uses sort-last compositing it is up to the user to ensure
  + * that the data distribution across the nodes is suitable. Specifically,
  + * each nodes data must be convex, and disjoint. This renderer only
  + * supports a single volume per node but within the volume could be
  + * arbitrary geometry.
  + *
  + * In the case that you have geometry crossing the boundary of nodes
  + * and are replicating it on both nodes to render (ghost zones, etc.)
  + * you can specify the clipBox for the renderer to clip rays against
  + * its data region, keeping the regions disjoint. For example, if a
  + * sphere center is on the border between two nodes, each would
  + * render half the sphere and the halves would be composited to produce
  + * the final whole-sphere in the image.
  + */
  +
  +namespace ospRandSciVisTest {
  using namespace ospcommon;
  @@ -101,7 +118,9 @@ namespace ospRandSphereTest {
  // Generate spheres within this nodes volume, to keep the data disjoint.
  // We also leave some buffer space on the boundaries to avoid clipping
  // artifacts or needing duplication across nodes in the case a sphere
  - // crosses a boundary.
  + // crosses a boundary. Note: Since we don't communicated ghost regions
  + // among the nodes, we make sure not to generate any spheres which would
  + // be clipped.
  std::uniform_real_distribution<float> dist_x(bbox.lower.x + sphereRadius,
  bbox.upper.x - sphereRadius);
  std::uniform_real_distribution<float> dist_y(bbox.lower.y + sphereRadius,
  @@ -274,6 +293,8 @@ namespace ospRandSphereTest {
  renderer.set("model", model);
  renderer.set("camera", camera);
  renderer.set("bgColor", vec3f(0.01f, 0.01f, 0.01f));
  + renderer.set("clipBox.lower", volume.second.lower);
  + renderer.set("clipBox.upper", volume.second.upper);
  renderer.commit();
  ospray::cpp::FrameBuffer fb(fbSize,OSP_FB_SRGBA,OSP_FB_COLOR|OSP_FB_ACCUM);
  @@ -329,5 +350,5 @@ namespace ospRandSphereTest {
  return 0;
  }
  -} // ::ospRandSphereTest
  +}
  