The blenderVR XML configuration file is loaded by the console (see Console vs virtual environment) to get the architecture related information to run blenderVR and send it to each rendering node (“virtual environment” part).

This file must contain at least four sections, plus the plugins section. It also includes a blenderVR section which only option is the network port used for the synchronization between the rendering nodes.

Some elements can be specific to one node, other shared. For instance, the blenderplayer executable can be the same for all rendering nodes or different on some nodes. In such case, there will be a section called system that can be inherited by each computer sub-section:

<computers>
  <system>
    <blenderplayer executable='/usr/local/blender/2.69/bin/blenderplayer' />
  </system>
  <computer name='front computer' hostname='front.fqdn'>
    <system>
      <blenderplayer executable='/usr/bin/blenderplayer' />
    </system>
  </computer>
  <computer name='left computer' hostname='left.fqdn' />
  <computer name='right computer' hostname='right.fqdn' />
</computers>

In this example, left computer and right computer nodes will use /usr/local/blender/2.69/bin/blenderplayer whereas front computer node will use /usr/bin/blenderplayer.

The system section is called rendundant as many entries will use the same information

In the XML file, you can use back-quote to execute code. First, the XML parser will try to execute this code as python code in blenderVR environment system (with all variables and import present in the blenderVR XML parser). If it fails, then, it tries as bash code and take the stdout result. If none is valid it raises an error.

For instance,

<environment>HOME=`os.environ['HOME']`</environment>

will define an environment variable (passed to the daemon or blenderplayer) called HOME that contains the current value of HOME operating system environment variable (with os.environ python code).

You can even use inherited values from redundant section:

<login remote_command="ssh `self._attributs_inheritance['hostname']`">

used inside the system redundant section will specify that remote_command will include the hostname as given in the computer entry.

If uncertain, we suggest you to simply print the self._attributs_inheritance python dictionary:

<login remote_command="`print(self._attributs_inheritance)`">

that will raise an exception (which is the point, since your purpose here is to create your configuration file, not to run blenderVR)

This section only concerns the console. It contains all screen sets definitions.

<starter>
  <config name='console'>console</config>
  <config name='virtual environment'>console, front screen, left screen, right screen</config>
  ...
</starter>

You can also add a hostname attribute in case of socket.gethostname() python function returns wrong hostname. This hostname is used by all “virtual environment” nodes to contact the console for network connection control.

Each config sub-section must list all screens, separated by commas, used by this screen set.

On some devices, the paths are not homogenous: the root path (repository) of .blend files on the console is not the same than on the master and/or on the slaves.

To fix that, blenderVR uses the notion of Anchor: it is a node specific absolute path on all nodes that prefixes each relative path for blender and processor files.

It is a kind of least common multiple path. For instance, with two computers:
console blender files repository: /home/me/blender_files
master node blender files repository: /remote_home/me/blender_files
This least common path is /home on the console and /remote_home on the master node (me/blender_files are common on both systems).

In such case, the starter section (console specific section) will start by:

<starter anchor='/home'>

Whereas system section for the master node will start by:

<system anchor='/remote_home'>

Each user must be listed here. Several users will e.g. enable you to attach a head tracker to adapt stereoscopic rendering to different points of view inside the virtual environment.

The behavior redundant section can define the default_position (0.0, 0.0, 0.0 by default) or the eye_separation (6 centimeters by default) of the user.

<!-- users section with default values -->
<users>
  <behavior eye_separation='0.06'>
    <default_position>0.0, 0.0, 0.0</default_position>
  </behavior>
  <user name="user A" />
</users>

We must describe how each rendering node (computer) works: each computer can have a specific configuration to run blenderplayer (paths, environment variables …). However, most of the time, all computers are equivalent. Redundant section is useful!

Computer itself must have a name and a hostname. The name will be used by the screen.

<computers>
  <system>
    ... <!-- computers global information -->
  </system>
  <computer name='front computer' hostname='front.fqdn'>
    <system>
      ... <!-- front computer specific information -->
    </system>
  </computer>
  <computer name='left computer' hostname='left.fqdn' />
</computers>

The system redundant section defines many things:

<system root='C:\\program\\blenderVR' anchor='U:\\blender_files'>
  <login remote_command="ssh `self._attributs_inheritance['hostname']`"/>
  <daemon>
    <environment>SystemRoot=C:\\Windows</environment>
  </daemon>
  <blenderplayer executable='C:\\blenderCave\\blender\\v2.70a\\blenderplayer.exe'>
    <environment>PYTHONPATH=C:\\Python33\\Lib;</environment>
  </blenderplayer>
</system>

The root parameter specifies the root path of blenderVR (where resides the blenderVR python script, the modules folder, etc.). By default, it is set to blenderVR root path on the console computer. However, due to not homogenous paths between nodes, you may have to define it for each system.

See Anchor to know the purpose of anchor parameter.

This section explains how to connect console and hosts computers.

<login remote_command="ssh me@host" python="/usr/bin/python3"/>

or

<login remote_command="psexec -d \\host" python="C:\\python33\\python.exe"/>

remote_command specifies the command, from the computer running the console to connect to the remote host.
python contains the path and the name of the python3 executable.

Generally, we use redundant system section with code execution to create this section (see example of the redundant section upper).

The daemon sub-section explains how to run the daemon (now that we know how to connect to the remote computer).

<daemon transmit='True'>
  <environment>SystemRoot=C:\\Windows</environment>
</daemon>

transmit parameter specifies if the daemon must transmit the environment variables to blenderplayer while it runs it.
environment sub-section adds some specific environment variable to the daemon.

This section defines how to run blenderplayer.

<blenderplayer executable='C:\\blenderVR\\blender\\v2.69\\blenderplayer.exe'>
  <environment>PYTHONPATH=C:\\Python33\\Lib;C:\\Python33\\DLLs;C:\\Python33\\Lib\\site-packages</environment>
</blenderplayer>

The executable parameter contains the path and the binary name of patched version of blenderplayer.
The environment sub-sections allows you to add specific environment variables for blenderplayer. You can add PYTHONPATH environment to specify paths for optional modules (such as for VRPN).

The screen is the unit of rendering: there is bijection between screen and instance of blenderplayer. Each screen has a name and a computer (actually the name of the computer section, above).

<screens>
  <display>
    ... <!-- screens global informations -->
  </display>
  <screen name='front screen' computer='front computer'>
    <display>
      ... <!-- front screen specific informations -->
    </display>
    <wall>
      ...
    </wall>
  </screen>
  <screen name='left screen' computer='left computer'>
</screens>

The display redundant section defines several things:

• options passed as argument to blenderplayer (for instance, -f -s hwpageflip to request a stereoscopic full screen blenderplayer window).
• environment to pass specific environment variables to blenderplayer.
• graphic_buffer to associate:
  • buffer (alone = no stereo, left graphic buffer or right graphic buffer,
  • user (as given inside users section),
  • eye of the user (left, middle or right).
• viewport to reduce the screen (usefull if you have occlusion).

<display options='-w 400 400'>
  <viewport>420, 0, 1500, 1080</viewport>
  <environment>DISPLAY=:0.0</environment>
  <graphic_buffer buffer='alone' user='user A' eye='middle'/>
</display>

Each screen must have one sub-section wall or hmd.

Wall or HMD differs in the way they manage the projection. Wall screens are fixed in the real world but HMD screen are attached to head of the user, moving along.

Both require a screen definition: three corners (top right, top left and bottom right):

<wall or hmd>
  <corner name="topRightCorner">1.0, 1.0, -1.0</corner>
  <corner name="topLeftCorner">-1.0, 1.0, -1.0</corner>
  <corner name="bottomRightCorner">1.0, -1.0, -1.0</corner>
</wall or /hmd>

For Wall, the screens are defined in vehicle reference frame. For HMD, the screens are defined in the reference frame of head tracker.

This sample configuration file can be used for a cave with three vertical square (2 m x 2 m) screens (left, front and right) plus a console computer with a single windowed screen.

config.xml

<?xml version="1.0"?>
<blenderVR>
 
  <starter anchor='/tmp/console'>
      <config name='console'>console screen</config>
      <config name='virtual environment'>console screen, front screen, left screen, right screen</config>
  </starter>
 
  <users>
    <user name='user A' />
  </users>
 
  <!-- Here, we define the console parameters -->
  <computers>
    <computer name='console computer' hostname='console.fqdn'/>
  </computers>
  <screens>
    <screen name='console screen' computer='console computer'>
      <display options='-w 600 600'>
	<environment>DISPLAY=:0.0</environment>
	<graphic_buffer user='user A'/>
      </display>
      <wall>
	<corner name='topRightCorner'>1.0, 1.0, -1.0</corner>
	<corner name='topLeftCorner'>-1.0, 1.0, -1.0</corner>
	<corner name='bottomRightCorner'>1.0, -1.0, -1.0</corner>
      </wall>
    </screen>
  </screens>
 
  <computers>
    <system root='/usr/local/blender/vr/1.0' anchor='/tmp/node'>
      <login remote_command="ssh `self._attributs_inheritance['hostname']`" python='/usr/local/blender/2.69/dependencies/bin/python3.3'/>
      <daemon transmit='True'>
	<environment>PATH=/usr/bin:/bin</environment>
      </daemon>
      <blenderplayer executable='/usr/local/blender/2.69/bin/blenderplayer' />
    </system>
    <computer name='front computer' hostname='front.fqdn' />
    <computer name='right computer' hostname='right.fqdn' />
    <computer name='left computer' hostname='left.fqdn' />
  </computers>
  <screens>
    <display options='-f -s hwpageflip'>
      <environment>DISPLAY=:0.0</environment>
      <graphic_buffer buffer='left' user='user A' eye='left'/>
      <graphic_buffer buffer='right' user='user A' eye='right'/>
    </display>
    <screen name='front screen' computer='front computer'>
      <wall>
	<corner name='topRightCorner'>1.0, 1.0, -1.0</corner>
	<corner name='topLeftCorner'>-1.0, 1.0, -1.0</corner>
	<corner name='bottomRightCorner'>1.0, -1.0, -1.0</corner>
      </wall>
    </screen>
    <screen name='left screen' computer='left computer'>
      <wall>
	<corner name='topRightCorner'>-1.0, 1.0, -1.0</corner>
	<corner name='topLeftCorner'>-1.0, 1.0, 1.0</corner>
	<corner name='bottomRightCorner'>-1.0, -1.0, -1.0</corner>
      </wall>
    </screen>
    <screen name='right screen' computer='right computer'>
      <wall>
	<corner name='topRightCorner'>1.0, 1.0, 1.0</corner>
	<corner name='topLeftCorner'>1.0, 1.0, -1.0</corner>
	<corner name='bottomRightCorner'>1.0, -1.0, 1.0</corner>
      </wall>
    </screen>
  </screens>
 
  <plugins>
    <vrpn>
      <floor x='0.0'/>
      <tracker device='GTK' host='localhost'>
	<transformation>
	  <post_translation z='-1.6'/>
	  <post_rotation x='1.0' y='1.0' z='1.0' angle="`-2*math.pi/3`"/>
	  <pre_rotation x='1.0' y='1.0' z='1.0' angle="`2*math.pi/3`"/>
	</transformation>
	<sensor id='0' processor_method='user_position' users='user A'/>
	<sensor id='1' processor_method='tracker_1'/>
	<sensor id='2' processor_method='tracker_2'/>
	<sensor id='3' processor_method='tracker_3'/>
      </tracker>
      <analog device='GTK' host='localhost' processor_method='movements'/>
      <button device='GTK' host='localhost' processor_method='buttons'/>
    </vrpn>
  </plugins>
</blenderVR>