Code for In Situ Exploration of Particle Simulations with CPU Ray Tracing
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README.md

OSPRay In Situ Particles Module

This is a module for the OSPRay ray tracer and library for simulations that implements the in situ particle rendering system described in the paper W. Usher, I. Wald, A. Knoll, M. Papka, V. Pascucci. "In Situ Exploration of Particle Simulations with CPU Ray Tracing", Supercomputing Frontiers and Innovations, 2016.

Building the In Situ Library

To integrate the code in your simulation and build the rendering client in OSPRay you first need to build the in situ data management library under libIS/. This will build the simulation side library lib_is_sim and the client side library lib_is_render which you can use to integrate into your simulation and make a rendering client respectively. Examples are provided in libIS/test_sim.cpp and libIS/test_render.cpp.

Building the In Situ Rendering Client

We also provide an in situ particle rendering client built using lib_is_render which connects to simulations using lib_is_sim and renders the particle data using P-k-d trees. The P-k-d code has some modifications to extend it to a data-distributed setting along with a renderer based on OSPRay's existing data-distributed volume renering. This code is built as a regular OSPRay module, to test it you can run the test sim and connect using the module. OSPRay must also be built with app scripting enabled to use the in situ particles code in the existing glut viewer.

The client requires v1.1.2 of OSPRay due to some recent reworking of the way devices are handled changing the MPI device and distributed rendering code in OSPRay some.

Running

Once the module is built you can run the test simulation and connect to it in the GLUT viewer. Once running the simulation library will listen on port 29374, which you can then connect to and query using functions exposed to the viewer scripting. First launch the GLUT viewer and load the in situ particles module and use its renderer. In this case we run two worker processes and split the world in a 2x1x1 grid with the OSPRAY_DATA_PARALLEL environment variable, so each worker will get half the world's data to render. Note that you should not specify the isp renderer on the command line as it doesn't support scenes without in situ particle data, so after creating the geometry you can make and set the renderer.

OSPRAY_DATA_PARALLEL=2x1x1 mpirun -np 3 ./ospGlutViewer \
  --module in_situ_particles --osp:mpi

To poll a timestep once from the simulation enter the following in the viewer's scripting console:

var isp_renderer = Renderer("isp");
var bounds = box3f();
var iss = ispPollOnce(isp_renderer, "localhost", 29374, 0.015, bounds);
m.addGeometry(iss);

isp_renderer.set("camera", c);
isp_renderer.set("model", m);
// Note: This MUST be run as a single line so the previous renderer
// which doesn't support the ISP geometry doesn't see a partial/invalid
// world state.
isp_renderer.commit(); m.commit(); setRenderer(isp_renderer);

setWorldBounds(bounds);
print(bounds);
refresh();

The function ispPollOnce requests a single timestep from the simulation. Another function ispPollSim is also available which will repeatedly get timesteps from the simulation and call a user provided callback. Note that this requires a missing manual script locking feature in OSPRay which I implemented on a fork for this project, the feature still works but cannot be used from a script. This is shown in insituspheres.chai, which you can pass as a start script to the GLUT viewer instead of typing the previous commands interactively:

OSPRAY_DATA_PARALLEL=2x1x1 mpirun -np 3 ./ospGlutViewer \
  --module in_situ_particles --osp:mpi --script insituparticles.chai