COVISE and OpenCOVER support

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Contents

Lab hardware

We are using Suse Linux 10.0 on most of our lab machines. The names of the lab machines you have an account on are:

  • coutsound.ucsd.edu: AMD Opteron based file server and computer connected to dual-head setup next to projectors. Use this machine to compile and to change your password. Let me know when you change your password so that I can update it on the rest of the lab machines.
  • visualtest01.ucsd.edu: AMD Opteron based, drives lower half of c-wall
  • visualtest02.ucsd.edu: AMD Opteron based, drives upper half of c-wall
  • flint.ucsd.edu: Intel Pentium D based Dell in terminal room
  • chert.ucsd.edu: Intel Pentium D based Dell in terminal room
  • basalt.ucsd.edu: Intel Pentium D based Dell in terminal room
  • rubble.ucsd.edu: Intel Pentium D based Dell in terminal room
  • slate.ucsd.edu: Intel Pentium D based Dell in terminal room

Due to the different computer hardware we use in the terminal room and the cave room, you should always compile your plugins on coutsound. All these machines can be accessed from the public internet. You can log in with your username by using ssh. Example for user 'jschulze' logging into 'flint': ssh jschulze@flint.ucsd.edu

Account information

In order to cross login between lab machines without a password you will need to create a DSA key pair. To generate this you run the command 'ssh-keygen -t dsa' on any lab machine and use the default file names, and do not enter a pass phrase. This should generate two files in your ~/.ssh/ directory: id_dsa and id_dsa.pub. The last step is to copy the file id_dsa.pub to new file authorized_keys, or append the contents of id_dsa.pub to authorized_keys if it already exists.

General information about Covise modules

The entire Covise installation, including all plugins, is located at ~jschulze/covise/. Each user should have a link in their home directory named 'covise' which points to this directory. There should also be a link 'plugins' which points to the plugins directory. You should put all the plugins you write in this course into the directory: plugins/cse291/.

Other directories you might need throughout the project are:

  • covise/src/renderer/OpenCOVER/kernel/: core OpenCOVER functionality, especially coVRModuleSupport.cpp
  • covise/src/kernel/OpenVRUI/: OpenCOVER's user interface elements. useful documentation in doc/html subdirectory; browse by running Firefox on index.html
  • covise/src/renderer/OpenCOVER/osgcaveui/: special CaveUI functions, not required in class but useful

You compile your plugin with the 'make' command. This creates a library file in covise/amd64/lib/OpenCOVER/plugins/. Covise uses qmake, so the make file is being generated by the .pro file. The name of the plugin is determined by the project name in the .pro file in your plugin directory (first line, keyword TARGET). I defaulted TARGET to be p1<username> for project #1. It is important that the TARGET name be unique, or else you will overwrite somebody else's plugin. You can change the name of your source files or add additional source files (.cpp,.h) by listing them after the SOURCES tag in the .pro file.

You run OpenCOVER by typing 'opencover' anywhere at the command line. You quit opencover by hitting the 'q' key on the keyboard or ctrl-c in the shell window you started it from.

Good examples for plugins are plugins/Volume and plugins/PDBPlugin. Look at the code in these plugins to find out how to add menu items and how to do interaction. Note that there are two ways to do interaction: with pure OpenCOVER routines, or with OSGCaveUI. In this course we will try to use only OpenCOVER's own routines. Plugins do not get loaded by opencover before they are configured in the configuration file.

Important Directories

Covise configuration files

The configuration files are in the directory $HOME/covise/config/. In class, the only files you need to look at are:

  • config.ucsd.xml: general configuration information for all lab machines, except the c-wall machines
  • config.calitcwall.xml: C-wall specific configuration information (visualtest02.ucsd.edu)
  • config.calitvarrier.xml: Varrier specific configuration information (varrier.ucsd.edu)

The configuration files are XML files which can be edited with any ASCII text editor (vi, emacs, nedit, gedit, ...). There are sections specific for certain machines. To load your plugin (e.g., p1jschulze) on one or more machines (e.g., chert and basalt), you need to add or modify a section to contain: 

 <LOCAL host="chert,basalt">
   <COVERConfig>
     <Module value="p1jschulze" name="p1jschulze"/>
   </COVERConfig>
 </LOCAL>

Screen configuration:

OpenCOVER requires the following global tags to be configured for a proper display configuration: PipeConfig, WindowConfig, and ChannelConfig. Another required tag, ScreenConfig, needs to be set on a node by node basis, because it differs for every screen. In the following example, a cluster with one graphics card (pipe) per rendering node, one large desktop in Twinview mode (window) of size 3840x1200 pixels, and two separate rendering windows (channels), each 1920x1200 pixels, are being configured. 

 <PipeConfig>
   <Pipe display=":0.0" name="0" screen="0" pipe="0" /> 
 </PipeConfig>
 <WindowConfig>
   <Window width="3840" comment="MAIN" window="0" pipeIndex="0" height="1200" left="0" bottom="0" name="0" decoration="false" /> 
 </WindowConfig>
 <ChannelConfig>
   <Channel windowIndex="0" stereoMode="LEFT" channel="0" left="0" width="1920" bottom="0" height="1200" comment="C_A" name="0" /> 
   <Channel windowIndex="0" stereoMode="LEFT" channel="1" left="1920" width="1920" bottom="0" height="1200" comment="C_B" name="1" /> 
 </ChannelConfig>

The display parameters for the tiles are set on a per node basis with the ScreenConfig tag. The following example configures two tiles for node 'tile-0-0'. On each tile, the visible screen dimensions are 520x325 millimeters. The centers of the monitors are offset from the world coordinate system horizontaly by -1100 and -570 millimeters, respectively, and -360 millimeters vertically. A proper configuration file will list a section like the one below for every rendering node. 

 <LOCAL host="tile-0-0.local">
   <COVER>
     <ScreenConfig>
       <Screen width="520" h="0.0" height="325" p="0.0" originX="-1100" comment="S_A" originY="0" r="0.0" name="0" originZ="-360" screen="0" /> 
       <Screen width="520" h="0.0" height="325" p="0.0" originX="-570"  comment="S_B" originY="0" r="0.0" name="1" originZ="-360" screen="1" /> 
     </ScreenConfig>
   </COVER>
 </LOCAL>

The head node needs to be configured in the same way. If you are navigating with a mouse on the head node, you probably want to configure a larger screen size for the head node, so that it covers a larger area of the tiled screen. You can do this by adjusting the width and height values, but you want to make sure that the aspect ratio of the new values corresponds to the one of the OpenCOVER window.

Change Default VRUI Menu Position/Size

Let WindowTitle be the title of the window (the text in its title bar). Then add the following section to the config file: 

  <COVER>
    <VRUI>
      <WindowTitle>
        <Menu>
          <Position x="0" y="0" z="0" />
          <Size value="1.0" />
        </Menu>
      </WindowTitle>
    </VRUI>
  </COVER>

Debugging OpenCover Plugins

OpenCover code can be debugged with gdb. If it throws a 'Segmentation Fault' make sure the core is getting dumped with 'unlimit coredumpsize'. Then you should find a file named 'core' or 'core.<pid>' in the directory you are running opencover from. Let's assume your latest core file is called core.4567 then you can run gdb with:

  • gdb ~/covise/amd64/bin/Renderer/OpenCOVER core.4567

RETURN through the startup screens until you get a command prompt. The two most important commands are:

  • bt: to display the stack trace. The topmost call is the one which caused the segmentation fault.
  • quit: to quit gdb

Documentation for gdb is at: http://sourceware.org/gdb/documentation/

Intersection testing

If you have wondered how you can find out if the wand pointer intersects your objects, here is a template routine for it. You need to pass it the beginning and end of a line you're intersecting with, in world coordinates. The line will be starting from the hand position and extend along the Y axis. 

#include <osgUtil/IntersectVisitor>

class IsectInfo     // this is an optional class to illustrate the return values of the accept() function
{
  public:
      bool       found;              ///< false: no intersection found
      osg::Vec3  point;              ///< intersection point
      osg::Vec3  normal;             ///< intersection normal
      osg::Geode *geode;             ///< intersected Geode
};

void getObjectIntersection(osg::Node *root, osg::Vec3& wPointerStart, osg::Vec3& wPointerEnd, IsectInfo& isect)
{
    // Compute intersections of viewing ray with objects:
    osgUtil::IntersectVisitor iv;
    osg::ref_ptr<osg::LineSegment> testSegment = new osg::LineSegment();
    testSegment->set(wPointerStart, wPointerEnd);
    iv.addLineSegment(testSegment.get());
    iv.setTraversalMask(2);

    // Traverse the whole scenegraph.
    // Non-Interactive objects must have been marked with setNodeMask(~2):     root->accept(iv);
    isect.found = false;
    if (iv.hits())
    {
        osgUtil::IntersectVisitor::HitList& hitList = iv.getHitList(testSegment.get());
        if(!hitList.empty())
        {
            isect.point     = hitList.front().getWorldIntersectPoint();
            isect.normal    = hitList.front().getWorldIntersectNormal();
            isect.geode     = hitList.front()._geode.get();
            isect.found     = true;
        }
    }
}

Tracker Data

Here is a piece of code to get the pointer (=wand) position (pos1) and a point 1000 millimeters from it (pos2) along the pointer line: 

   osg::Vec3 pointerPos1Wld = cover->getPointerMat().getTrans();
   osg::Vec3 pointerPos2Wld = osg::Vec3(0.0, 1000.0, 0.0);
   pointerPos2Wld = pointerPos2Wld * cover->getPointerMat();

This is the way to get the head position: 

   Vec3 viewerPosWld = cover->getViewerMat().getTrans();

Interaction handling

To register an interaction so that only your plugin uses the mouse pointer while a button on the wand is pressed, you want to use the TrackerButtonInteraction class. For sample usage see plugins/Volume. Here are the main calls you will need. Most of these functions go in the preFrame routine, unless otherwise noted:

  • Make sure you include at the top of your code: 
     
      #include <OpenVRUI/coTrackerButtonInteraction.h>
  • In the constructor you want to create your interaction for button A, which is the left wand button: 
          interaction = new coTrackerButtonInteraction(coInteraction::ButtonA,"MoveObject",coInteraction::Menu);
  • In the destructor you want to call: 
          delete interaction;
  • To register your interaction and thus disable button A interaction in all other plugins call the following function. Make sure that to call this function before other modules can register the interaction. In particular, this might mean that you need to register the interaction before a mouse button is pressed, for instance by registering it when intersecting with the object to interact with. 
          if(!interaction->registered)
      {
         coInteractionManager::the()->registerInteraction(interaction);
      }
  • To do something just once, after the interaction has just started: 
          if(interaction->wasStarted())
      {
      }
  • To do something every frame while the interaction is running: 
         if(interaction->isRunning())
     {
     }
  • To do something once at the end of the interaction: 
         if(interaction->wasStopped())
     {
     }
  • To unregister the interaction and free button A for other plugins: 
          if(interaction->registered && (interaction->getState()!=coInteraction::Active))
      {
         coInteractionManager::the()->unregisterInteraction(interaction);
      }

OSG Text

Make sure you #include <osgText/Text>. There is a good example for how osgText can be used in ~/covise/src/renderer/OpenCOVER/osgcaveui/Card.cpp. _highlight is the osg::Geode the text gets created for, createLabel() returns the Drawable with the text, _labelText is the text string, and osgText::readFontFile() reads the font.

How to Create a Rectangle with a Texture

The following code sample from osgcaveui/Card.cpp demonstrates how to create a rectangular geometry with a texture. 

Geometry* Card::createIcon()
{
  Geometry* geom = new Geometry();

  Vec3Array* vertices = new Vec3Array(4);
  float marginX = (DEFAULT_CARD_WIDTH  - ICON_SIZE * DEFAULT_CARD_WIDTH) / 2.0;
  float marginY = marginX;
                                                  // bottom left
  (*vertices)[0].set(-DEFAULT_CARD_WIDTH / 2.0 + marginX, DEFAULT_CARD_HEIGHT /
2.0 - marginY - ICON_SIZE * DEFAULT_CARD_WIDTH, EPSILON_Z);
                                                  // bottom right
  (*vertices)[1].set( DEFAULT_CARD_WIDTH / 2.0 - marginX, DEFAULT_CARD_HEIGHT /
2.0 - marginY - ICON_SIZE * DEFAULT_CARD_WIDTH, EPSILON_Z);
                                                  // top right
  (*vertices)[2].set( DEFAULT_CARD_WIDTH / 2.0 - marginX, DEFAULT_CARD_HEIGHT /
2.0 - marginY, EPSILON_Z);
                                                  // top left
  (*vertices)[3].set(-DEFAULT_CARD_WIDTH / 2.0 + marginX, DEFAULT_CARD_HEIGHT /
2.0 - marginY, EPSILON_Z);
  geom->setVertexArray(vertices);

  Vec2Array* texcoords = new Vec2Array(4);
  (*texcoords)[0].set(0.0, 0.0);
  (*texcoords)[1].set(1.0, 0.0);
  (*texcoords)[2].set(1.0, 1.0);
  (*texcoords)[3].set(0.0, 1.0);
  geom->setTexCoordArray(0,texcoords);

  Vec3Array* normals = new Vec3Array(1);
  (*normals)[0].set(0.0f, 0.0f, 1.0f);
  geom->setNormalArray(normals);
  geom->setNormalBinding(Geometry::BIND_OVERALL);

  Vec4Array* colors = new Vec4Array(1);
  (*colors)[0].set(1.0, 1.0, 1.0, 1.0);
  geom->setColorArray(colors);
  geom->setColorBinding(Geometry::BIND_OVERALL);

  geom->addPrimitiveSet(new DrawArrays(PrimitiveSet::QUADS, 0, 4));

  // Texture:
  StateSet* stateset = geom->getOrCreateStateSet();
  stateset->setMode(GL_LIGHTING, StateAttribute::OFF);
  stateset->setRenderingHint(StateSet::TRANSPARENT_BIN);
  stateset->setTextureAttributeAndModes(0, _icon, StateAttribute::ON);

  return geom;
}

Load and display an image from disk

Here is sample code to create a geode (imageGeode) with an image which gets loaded from disk. OpenGL's size limitation for textures applies (usually 4096x4096 pixels). The image might have to have powers of two edges, but that limitation should not hold anymore on newer graphics cards. 

/** Loads image file into geode; returns NULL if image file cannot be loaded */
Geode* createImageGeode(const char* filename)
{
  // Create OSG image:
  Image* image = new Image();
  image = osgDB::readImageFile(filename);

  // Create OSG texture:
  if (image)
  {
    imageTexture = new Texture2D();
    imageTexture->setImage(image);
  }
  else 
  {
    std::cerr << "Cannot load image file " << filename << std::endl;
    delete image;
    return NULL;
  }

  // Create OSG geode:
  imageGeode = new Geode();
  imageGeode->addDrawable(createImageGeometry());
  return imageGeode;
}

/** Used by createImageGeode() */
Geometry* createImageGeometry()
{
  const float WIDTH  = 3.0f;
  const float HEIGHT = 2.0f;
  Geometry* geom = new Geometry();

  // Create vertices:
  Vec3Array* vertices = new Vec3Array(4);
  (*vertices)[0].set(-WIDTH / 2.0, HEIGHT / 2.0, 0); // bottom left
  (*vertices)[1].set( WIDTH / 2.0, HEIGHT / 2.0, 0); // bottom right
  (*vertices)[2].set( WIDTH / 2.0, HEIGHT / 2.0, 0); // top right
  (*vertices)[3].set(-WIDTH / 2.0, HEIGHT / 2.0, 0); // top left
  geom->setVertexArray(vertices);

  // Create texture coordinates for image texture:
  Vec2Array* texcoords = new Vec2Array(4);
  (*texcoords)[0].set(0.0, 0.0);
  (*texcoords)[1].set(1.0, 0.0);
  (*texcoords)[2].set(1.0, 1.0);
  (*texcoords)[3].set(0.0, 1.0);
  geom->setTexCoordArray(0,texcoords);

  // Create normals:
  Vec3Array* normals = new Vec3Array(1);
  (*normals)[0].set(0.0f, 0.0f, 1.0f);
  geom->setNormalArray(normals);
  geom->setNormalBinding(Geometry::BIND_OVERALL);

  // Create colors:
  Vec4Array* colors = new Vec4Array(1);
  (*colors)[0].set(1.0, 1.0, 1.0, 1.0);
  geom->setColorArray(colors);
  geom->setColorBinding(Geometry::BIND_OVERALL);

  geom->addPrimitiveSet(new DrawArrays(PrimitiveSet::QUADS, 0, 4));

  // Set texture parameters:
  StateSet* stateset = geom->getOrCreateStateSet();
  stateset->setMode(GL_LIGHTING, StateAttribute::OFF);  // make texture visible independent of lighting
  stateset->setRenderingHint(StateSet::TRANSPARENT_BIN);  // only required for translucent images
  stateset->setTextureAttributeAndModes(0, imageTexture, StateAttribute::ON);

  return geom;
}

Wall Clock Time

If you are going to animate anything, keep in mind that the rendering system runs anywhere between 1 and 100 frames per second, so you can't rely on the time between frames being anything you assume. Instead, you will want to know exactly how much time has passed since you last rendered something, i.e., you last preFrame() call. You should use cover->frameTime(), or better cover->frameDuration(); these return a double value with the number of seconds (at an accuracy of milli- or even microseconds) passed since the start of the program, or since the last preFrame(), respectively.

Backtrack all nodes up to top of scene graph

osg::NodePath path = getNodePath();
ref_ptr<osg::StateSet> state = new osg::StateSet;
for (osg::NodePath::iterator it = path.begin(); it != path.end(); ++it)
{
  if ((*it)->getStateSet())
  {
    state->merge((*it)->getStateSet());
  }
}


Taking a screenshot from the command line

  • run application on visualtest02 and bring up desired image, freeze head tracking
  • log on to coutsound
  • Make sure screenshot is taken of visualtest02: setenv DISPLAY :0.0
  • Take screenshot: xwd -root -out <screenshot_filename.xwd>
  • Convert image file to TIFF: convert <screenshot_filename.xwd> <screenshot_filename.tif>

Taking a Screenshot from within OpenCOVER

osg::camera allows you to take a screenshot at higher than physical display resolution. Here is an example from the email thread at http://openscenegraph.org/archiver/osg-users/2007-April/0054.html using wxWindows. 

//save the old viewport:
osg::ref_ptr<osg::Viewport> AlterViewport = sceneView->getViewport();
osg::ref_ptr<osg::Image> shot = new osg::Image();
//shot->setPixelFormat(GL_RGB);

int w = 0; int h = 0;
GetClientSize(&w, &h);
float ratio = (float)w/(float)h;
w = 2500;
h = (int)((float)w/ratio);
//shot->scaleImage(w, h, 24);
shot->allocateImage(w, h, 24, GL_RGB, GL_UNSIGNED_BYTE);
osg::Node* subgraph = TheDocument->RootGroup.get();

osg::ref_ptr<osg::Camera> camera = new
osg::Camera(*(sceneView->getCamera()) );

// set view
camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);

// set viewport
camera->setViewport(0,0,w,h);

// set the camera to render before the main camera.
camera->setRenderOrder(osg::Camera::PRE_RENDER);

// tell the camera to use OpenGL frame buffer object where supported.
camera->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT);

camera->attach(osg::Camera::COLOR_BUFFER, shot.get());

// add subgraph to render
camera->addChild(subgraph);
//Need to mage it part of the scene :
sceneView->setSceneData(camera);

//Make it frame:
Update();
Refresh();

wxImage img;
img.Create(w, h);
img.SetData(shot->data());
shot.release();

wxImage i2 = img.Mirror(false);
i2.SaveFile(filename);
sceneView->setSceneData(subgraph);
sceneView->setViewport(AlterViewport.get() );

Another approach for a screenshot is to create an object derived from osg::Geometry, for instance a rectangle, and put the following code in its drawImplementation(). 

/** Copy the currently displayed OpenGL image to a memory buffer and
  resize the image if necessary.
  @param w,h image size in pixels
  @param data _allocated_ memory space providing w*h*3 bytes of memory space
  @return memory space to which volume was rendered. This need not be the same
          as data, if internal space is used.
*/
void takeScreenshot(int w, int h, uchar* data)
{
  uchar* screenshot;
  GLint viewPort[4];                              // x, y, width, height of viewport
  int x, y;
  int srcIndex, dstIndex, srcX, srcY;
  int offX, offY;                                 // offsets in source image to maintain aspect ratio
  int srcWidth, srcHeight;                        // actually used area of source image

  // Save GL state:
  glPushAttrib(GL_ALL_ATTRIB_BITS);

  // Prepare reading:
  glGetIntegerv(GL_VIEWPORT, viewPort);
  screenshot = new uchar[viewPort[2] * viewPort[3] * 3];
  glDrawBuffer(GL_FRONT);                         // set draw buffer to front in order to read image data
  glPixelStorei(GL_PACK_ALIGNMENT, 1);            // Important command: default value is 4, so allocated memory wouldn't suffice

  // Read image data:
  glReadPixels(0, 0, viewPort[2], viewPort[3], GL_RGB, GL_UNSIGNED_BYTE, screenshot);

  // Restore GL state:
  glPopAttrib();

  // Maintain aspect ratio:
  if (viewPort[2]==w && viewPort[3]==h)
  {                                               // movie image same aspect ratio as OpenGL window?
    srcWidth  = viewPort[2];
    srcHeight = viewPort[3];
    offX = 0;
    offY = 0;
  }
  else if ((float)viewPort[2] / (float)viewPort[3] > (float)w / (float)h)
  {                                               // movie image more narrow than OpenGL window?
    srcHeight = viewPort[3];
    srcWidth = srcHeight * w / h;
    offX = (viewPort[2] - srcWidth) / 2;
    offY = 0;
  }
  else                                            // movie image wider than OpenGL window
  {
    srcWidth = viewPort[2];
    srcHeight = h * srcWidth / w;
    offX = 0;
    offY = (viewPort[3] - srcHeight) / 2;
  }

  // Now resample image data:
  for (y=0; y<h; ++y)
  {
    for (x=0; x<w; ++x)
    {
      dstIndex = 3 * (x + (h - y - 1) * w);
      srcX = offX + srcWidth  * x / w;
      srcY = offY + srcHeight * y / h;
      srcIndex = 3 * (srcX + srcY * viewPort[2]);
      memcpy(data + dstIndex, screenshot + srcIndex, 3);
    }
  }
  delete[] screenshot;
}

Return a ref_ptr from a function

Here is a safe way to return a ref_ptr type from a function. 

osg::ref_ptr<osg::Group> makeGroup(...Some arguments..) 
{
  osg::ref_ptr<osg::MatrixTransform> mt=new MatrixTransform();
  // ...some operations...
  return mt.get();
}

Also check out this link to learn more about how to use ref_ptr: http://donburns.net/OSG/Articles/RefPointers/RefPointers.html

Occlusion Culling in OpenSceneGraph

Occlusion culling removes objects which are hidden behind other objects in the culling stage so they never get rendered, thus resulting in a higher rendering rate. In covise/src/renderer/OpenCOVER/kernel/VRViewer.cpp, the SceneView is being created. By default CullingMode gets set like this: 

  osg::CullStack::CullingMode cullingMode = cover->screens[i].sceneView->getCullingMode();
  cullingMode &= ~(osg::CullStack::SMALL_FEATURE_CULLING);
  cover->screens[i].sv->setCullingMode(cullingMode);

There are several types of culling options available. However, the easiest way to test your culling code would be to set the cullingMode to ENABLE_ALL_CULLING.

There isn't any way to automatically add occlusion culling to a scene, you'll need to insert convex planar occluders into your scene. See the for inspiration. Be sure to check out the plugins that use occluders. The Calit2Building plugin shows the use of occluders generated from a .osg file of the model (/local/home/jschulze/svn/trunk/covise/src/renderer/OpenCOVER/plugins/Calit2Building). However for a simple example of basic occlusion manipulation with matrix transforms be sure to visit the OccluderHelper plugin (/local/home/jschulze/svn/trunk/covise/src/renderer/OpenCOVER/plugins/OccluderHelper). If you're looking for code snippets check out this osgoccluder example or look at the pseudo code below to see a nice green occlusion plane based on four points you can hard code in: 


using namespace osg;

int Main()
{
	Group *res = createOcclusionFromPoints();
	cover->getObjectsRoot()->addChild(res);
        return 0;
}

Group*
OccluderHelper::createOcclusionFromPoints()
{
	const Vec3& point1 = Vec3(point1X, point1Y, point1Z);                  //define the points of the plane
	const Vec3& point2 = Vec3(point2X, point2Y, point2Z);
	const Vec3& point3 = Vec3(point3X, point3Y, point3Z);
	const Vec3& point4 = Vec3(point4X, point4Y, point4Z);	
        MatrixTransform occluderMT = new MatrixTransform();
        occluderMT->addChild(createOcclusion(point3, point1, point4, point2));  //note the order
	Group *scene = new Group();
	scene->setName("rootgroup");

	scene->addChild(occluderMT);	
	
	return scene;
}


Node* 
OccluderHelper::createOcclusion(const Vec3& v1, const Vec3& v2, const Vec3& v3, const Vec3& v4)
{
	// create and occluder which will site along side the loadmodel model.
	OccluderNode* occluderNode = new OccluderNode;

	// create the convex planer occluder 
    	ConvexPlanarOccluder* cpo = new ConvexPlanarOccluder;

    	// attach it to the occluder node.
   	occluderNode->setOccluder(cpo);
   	occluderNode->setName("occluder");
    
    	// set the occluder up for the front face of the bounding box.
    	ConvexPlanarPolygon& occluder = cpo->getOccluder();
    	occluder.add(v1);
    	occluder.add(v2);
    	occluder.add(v3);
    	occluder.add(v4);   

   	// create a drawable for occluder.
    	Geometry* geom = new Geometry;
    
    	Vec3Array* coords = new Vec3Array(occluder.getVertexList().begin(),occluder.getVertexList().end());
    	geom->setVertexArray(coords);
    
    	Vec4Array* colors = new Vec4Array(1);
    	(*colors)[0].set(0.0f,1.0f,0.0f,0.5f);
    	geom->setColorArray(colors);
    	geom->setColorBinding(Geometry::BIND_OVERALL);
    
    	geom->addPrimitiveSet(new DrawArrays(PrimitiveSet::QUADS,0,4));
    
    	Geode* geode = new Geode;
    	geode->addDrawable(geom);
    
    	StateSet* stateset = new StateSet;
    	stateset->setMode(GL_LIGHTING,StateAttribute::OFF);
    	stateset->setMode(GL_BLEND,StateAttribute::ON);
    	stateset->setRenderingHint(StateSet::TRANSPARENT_BIN);
    
    	geom->setStateSet(stateset);
       	occluderNode->addChild(geode);    
   
    	return occluderNode;
}

If you have access to 3D Studio Max, you can find instructions on how to install and use the OSG exporter which gives you access to culling and LOD helpers for your 3D models. However, 3ds 9 is not stable with osgExp and will not allow you to have access to these occluderHelpers. I am unaware of any progress to improve osgExp for the newer versions of 3ds. If you choose this option, use it with the stable 3ds 8 or 7 with osgExp version 9.3. Otherwise check out the Calit2Building plugin which manually generates occlusion planes on OpenCOVER based on geometry created in 3ds by parsing through the .osg export file.

Check out the osgoccluder example located in: svn/extern_libs/amd64/OpenSceneGraph-svn/OpenSceneGraph/examples

An alternative to occlusion culling is to use LOD (level of detail) nodes in the scene graph. This means that when you are farther away, less polygons get rendered. See the osglod example for inspiration.

Message Passing in OpenCOVER

This is how you can send a message from the master to all nodes in the rendering cluster. These functions are defined in covise/src/renderer/OpenCOVER/kernel/coVRMSController.h. 

if(coVRMSController::instance()->isMaster())
{
  coVRMSController::instance()->sendSlaves((char*)&appReceiveBuffer,sizeof(receiveBuffer));
}
else
{
  coVRMSController::instance()->readMaster((char*)&appReceiveBuffer,sizeof(receiveBuffer));
}

The above functions make heavy use of the class coVRSlave (covise/src/renderer/OpenCOVER/kernel/coVRSlave.h). This class uses the Socket class to implement the communication between nodes. The Socket class can be used, using a different port, to implement communication between rendering nodes.

Notice that the above functions are for communication WITHIN a rendering cluster. In order to send a message to a remote OpenCOVER (running on another rendering cluster connected via a WAN) you would use cover->sendMessage. The source code for this function is at covise/src/renderer/OpenCOVER/kernel/coVRPluginSupport.h.

Moving an object with the pointer

Here is some sample code to move an object. object2w is the object's transformation matrix in world space. lastWand2w and wand2w are the wand matrices from the previous and current frames, respectively, from cover->getPointer(). 

void move(Matrix& lastWand2w, Matrix& wand2w)
{
    // Compute difference matrix between last and current wand:
    Matrix invLastWand2w = Matrix::inverse(lastWand2w);
    Matrix wDiff = invLastWand2w * wand2w;

    // Perform move:
    _node->setMatrix(object2w * wDiff);
}

Using Shared Memory

A great tutorial page is at: http://www.ecst.csuchico.edu/~beej/guide/ipc/shmem.html

Find out which node a plugin is running on

The following routine works on our Varrier system to find out the host number, starting with 0. The node names are vellum1-10, vellum2-10, etc. 

int getNodeIndex()
{
  char hostname[33];
  gethostname(hostname, 32);
  int node;
  sscanf(hostname, "vellum%d-10", &node);  // this needs to be adjusted to naming convention
  return (node-1);  // names start with 1
}


Hide or select different pointer

The pointer is by default a line coming out of the users's hand held device. Icons like an airplane, a steering wheel, slippers, or a magnifying glass indicate the current navigation mode. This is the mode the left mouse button will use. To hide the pointer, remove all geodes which are part of the pointer: 

  while(VRSceneGraph::instance()->getHandTransform()->getNumChildren())
    VRSceneGraph::instance()->getHandTransform()->removeChild(m_handScaledTransform->getChild(0));

To select a different pre-defined pointer: 

  VRSceneGraph::instance()->setPointerType(<new_type>);

Hide the mouse cursor

  osgViewer::Viewer::Windows windows;
  viewer.getWindows(windows);
  for(osgViewer::Viewer::Windows::iterator itr = windows.begin(); itr != windows.end(); ++itr)
  {
    (*itr)->useCursor(false);
  }

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