ParaView/Users Guide/CAVE Display

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( NOTE: This page is currently undergoing changes.)

Introduction

  • ParaView has basic support for visualization in CAVE-like/VR or Virtual Environments (VE).
  • Like typical computing systems, VE's consists of peripheral displays (output) and input devices. However, unlike regular systems, VE's keep track of the physical location of their IO devices with respect to an assumed base coordinates in the physical room (room coordinates).
  • Typically VE's consists of multiple stereoscopic displays that are configured based on the room coordinates. These base coordinates also typically serve as the reference coordinate for tracked inputs commonly found in VE's.
  • VR support in ParaView includes the ability to
  1. Configure displays (CAVE/Tiled Walls etc) and
  2. The ability to configure inputs using VRPN/VRUI.
  • ParaView can operate in a Client / Server fashion. The VR/CAVE module leverage this by assigning different processes on the server to manage different displays. Displays are thus configured on the server side by passing a *.pvx configuration XML file during start-up.
  • The client acts as a central point of control. It can initiate the scene (visualization pipeline) and also relay tracked interactions to each server process managing the displays. The VR plugin on the client side enables this. Device and interaction style configurations are brought in through the ParaView state file (This will also have a GUI component in the near future).

Architecture and Design

(content coming up) VRArch.png

Process to Build, Configure and Run ParaView in VE

Enabling ParaView for VR is a five stage process.

  1. Building ParaView with the required parameters.
  2. Preparing the display configuration file.
  3. Preparing the input configuration file.
  4. Starting the server (with display config.pvx)
  5. Starting the client (with input config.pvsm)

Building

Follow regular build instructions from http://paraview.org/Wiki/ParaView:Build_And_Install. In addition following steps needs to be performed

  • Make sure Qt and MPI are installed cause they are required for building. If using VRPN make sure it is build and installed as well.
  • When configuring cmake enable BUILD_SHARED_LIB, PARAVIEW_BUILD_QT_GUI, PARAVIEW_USE_MPI and PARAVIEW_BUILD_PLUGIN_VRPlugin .
  • On Apple and Linux platforms the Plugin uses VRUI device daemon client as its default and on Windows VRPN is the default.
  • If you want to enable the other simply enable PARAVIEW_USE_VRPN or PARAVIEW_USE_VRUI .
  • If VRPN is not found in the default paths then VRPN_INCLUDE_DIR and VRPN_LIBRARY may also need be set.

Configuring Displays

The PV server is responsible for configuring displays. The display configuration is stored on a *.pvx file.

Structure of PVX Config File

<?xml version="1.0" ?>
<pvx>
  <Process Type="server|dataserver|renderserver">
    <!-- 
      The only supported Type values are "server", "dataserver" or "renderserver".
      This controls which executable this configuration is applicable to.
      There can be multiple <Process /> elements in the same pvx file.
      ------------------------------------------------------
      |  Executable     | Applicable Process Type          |
      |  pvserver       | server, dataserver, renderserver |
      |  pvrenderserver | server, renderserver             |
      |  pvdataserver   | server, dataserver               |
      ------------------------------------------------------
     -->
    <Machine name="hostname"
             Environment="DISPLAY=m1:0"
             LowerLeft="-1.0 -1.0 -1.0"
             LowerRight="1.0 -1.0 -1.0"
             UpperRight="1.0  1.0 -1.0">
      <!--
         There can be multiple <Machine> elements in a <Process> element, 
         each one identifying the configuration for a process. 
         All attributes are optional.
         name="hostname"
         Environment: the environment for the process.
         LowerLeft|LowerRight|UpperRight 
       -->
    </Machine>
  </Process>
</pvx>

Example Config.pvx

  • The following example is for a six sided cave with origin at (0,0,0):
<?xml version="1.0" ?>
<pvx>
 <Process Type="client" />
 <Process Type="server">
  <Machine Name="Front"
           Environment="DISPLAY=:0"
           LowerLeft=" -1 -1 -1"
           LowerRight=" 1 -1 -1"
           UpperRight=" 1  1 -1" />
  <Machine Name="Right"
           Environment="DISPLAY=:0"
           LowerLeft="  1 -1 -1"
           LowerRight=" 1 -1  1"
           UpperRight=" 1  1  1" />
  <Machine Name="Left"
           Environment="DISPLAY=:0"
           LowerLeft=" -1 -1  1"
           LowerRight="-1 -1 -1"
           UpperRight="-1  1 -1"/>
  <Machine Name="Top"
           Environment="DISPLAY=:0"
           LowerLeft=" -1  1 -1"
           LowerRight=" 1  1 -1"
           UpperRight=" 1  1  1"/>
  <Machine Name="Bottom"
           Environment="DISPLAY=:0"
           LowerLeft=" -1 -1  1"
           LowerRight=" 1 -1  1"
           UpperRight=" 1 -1 -1"/>
  <Machine Name="Back"
           Environment="DISPLAY=:0"
           LowerLeft="  1 -1  1"
           LowerRight="-1 -1  1"
           UpperRight="-1  1  1"/>
  </Process>
</pvx>
  • A sample PVX is provided in ParaView/Documentation/cave.pvx. This can be used to play with different display configurations.

Notes on PVX file usage

  • PVX file should be specified as the last command line argument for any of the server processes.
  • The PVX file is typically specified for all the executables whose environment is being changed using the PVX file. In case of data-server/render-server configuration, if you are setting up the environment for the two processes groups, then the PVX file must be passed as a command line option to both the executables: pvdataserver and pvrenderserver.
  • When running in parallel the file is read on all nodes, hence it must be present on all nodes.

Configure Inputs

  • Configuring inputs is a two step process
  1. Define connections to one or more VRPN/VRUI servers.
  2. Mapping data coming in from the server to ParaView interactor styles.

Defining Connections

  • Connections are clients to VRPN servers and or VRUI device daemons.
  • Connection are defined using XML as follow.
 <VRConnectionManager>
    <VRUIConnection name="travel" address="localhost" port = "8555">
      <Button id="0" name="1"/>
      <Button id="1" name="2"/>
      <Button id="2" name="3"/>
      <Tracker id="0" name="head"/>
      <Tracker id="1" name="wand"/>
    </VRUIConnection>
    <VRPNConnection name="spaceNav" address="device0@localhost">
      <Analog id="0" name="channels"/>
    </VRPNConnection>
 </VRConnectionManager>
</pvx>
  • VRConnectionManager can define multiple connection. Each connection can of of type VRUIConnection or VRPNConnection.
  • Each connection has a name associated with it. Also data coming in from these connection can be given specific names.
  • In our example above a VRUI connection is defined and named travel. We also define a name to the tracking data on this connection calling it head. We can henceforth refer to this data using a dotted notation as follows
 travel.head
  • Like all data being read into the system can be assigned some virtual names which will be used down the line.
  • Following is a pictorial representation of the process.

ConnectionConfiguration (1).png

Interaction Styles

  • There are fixed number of hand-coded interaction styles.
  • Interactor styles are specified using the following XML format.

<style type=xml> </style> ParaviewVRPluginWorkflow.png

Linking devices to interaction styles

(content coming up) Device2InteractorStyleConfig.png

Start Server

  • On a terminal run the server (For example we want to run 6 processes each driving one display in the cave. Change the number of process according to the number of displays).
 # PV_ICET_WINDOW_BORDERS=1 mpiexec -np 6 ./pvserver  /path/to/ConfigFile.pvx

Note: PV_ICET_WINDOW_BORDERS=1 disables the full-screen mode and instead opens up a 400x400 window. Remove this environment variable to work in full-screen mode.

Start Client

  • Open another terminal to run the client. (note: this client connects to the server which open up 6 windows according to the config given in cave.pvx). Change the stereo-type according to preference (see # ./paraview --help).
 # ./paraview --stereo --stereo-type=Anaglyph --server=localhost
  • --server=localhost connects the client to the server.
  • Enable the VRPlugin on the client.
  • Load the state file (config.state) specifying VRPN or VRUI client connection and interaction styles.

Tips and Tricks