Basics:

Note: All of the examples in these sections are in C++. Since we only had one pipe, these examples are meant for situations in which one pipe is used and may need to be altered if more pipes are utilized. In Hank, the code examples belong in the file generic.C

• Channel Initialization
  • Set the Call backs, Earth-Sky model, Scene, etc. of each channel.
  • Set the Viewport and ViewOffsets for each channel.
• Drawing into different buffers
• Overlapping Viewports
• Buffer Swapping
• Querying the system for stereo
• Putting your monitor in stereo-mode

Channel Initialization

Table 1. Sharable attributes in a channel group

ex1: A simple declaration and initialization of 3 channels.

    void
    InitChannel(void)
    {
        /* The channels are often declared globally */
        pfChannel    *chan, *chan2, *chan3;

    /* Initialize and attach the channels */
        chan  = new pfChannel(pfGetPipe(0));
        chan2 = new pfChannel(pfGetPipe(0));
        chan3 = new pfChannel(pfGetPipe(0));

        /* Form a channel group with 'chan' as the master */
        chan->attach(chan2);
        chan->attach(chan3);

    /* Initialize all attributes shared between channels */
            /* Set the callback routines for the pfChannel */
            chan->setTravFunc(PFTRAV_APP, AppFunc);
            chan->setTravFunc(PFTRAV_CULL, CullFunc);
            chan->setTravFunc(PFTRAV_DRAW, DrawFunc);

            /* Attach the visual database to the channels */
            chan->setScene(scene);

            /* Attach the EarthSky model to the channels */
            chan->setESky(eSky);

            /* Initialize the near and far clipping planes */
            chan->setNearFar(near, far);

            /* Initialize the viewing position and direction */
            chan->setView(initView->xyz, initView->hpr);

           /* Set channel frustums */
           chan->setAutoAspect(PFFRUST_CALC_VERT);
           chan->makeSimple(fov); 

            .....
    }

ex2: Setting Viewports and ViewOffsets of 2 channels to create a stereo image.

    void
    InitChannel(void)
    {
        float    paralax = 0.5f   /* Convergence */
        float    ioc     = 0.02f  /* Intraocular distance */
        int      share;           /* Share mask */
        pfVec3   xyz, hpr;

        .....

        chan->attach(chan2);

        .....

    /* channels need to share a viewport ---> Viewports should be shared
       automatically.  This should be unnecessary unless multiple 
       pipes are used.*/
 
        /* Get the default */
        share = chan->getShare();

        /* Add in the viewport share bit */
        share |= PFCHAN_VIEWPORT;
        share &= ~PFCHAN_FOV;

        chan->setShare(share);

    /* Set the Viewport and ViewOffsets for both channels */
        chan->setViewport(0.0f, 1.0f, 0.0f, 1.0f);

        /* Set left channel offsets */
        hpr.set(paralax, 0.0f, 0.0f);
        xyz.set(-ioc, 0.0f, 0.0f);
        chan->setViewOffsets(xyz, hpr);

        /* Set right channel offsets */
        hpr.set(-paralax, 0.0f, 0.0f);
        xyz.set(ioc, 0.0f, 0.0f);
        chan2->setViewOffsets(xyz, hpr);      
 
        .....
    }

ex3: Setting the Viewports and Offsets of 2 channels with each view in a different direction. Click here for a picture of front and 45 degrees left views as seen from a car in Hank. (Click here for the same picture with a gap between the channels).

    void
    InitChannel(void)
    {
        pfVec3  xyz, hpr;
        float   fov = 45.0; 

        .....

    /* Set front channel offsets */
        chan->setViewport(1.0f/2.0f, 1.0f, 0.0f, 1.0f);
        hpr.set(0.0f, 0.0f, 0.0f);
        xyz.set(0.0f, 0.0f, 0.0f);
        chan->setViewOffsets(xyz, hpr);

    /* Set left channel offsets */
        chan2->setViewport(0.0f, 1.0f/2.0f, 0.0f, 1.0f);
        hpr.set(45.0f, 0.0f, 0.0f);
        xyz.set(0.0f, 0.0f, 0.0f);
        chan2->setViewOffsets(xyz, hpr);     

        .....
    { 

Drawing into the different buffers

ex4: Choosing a buffer by alternating with each call to the draw callback.

    void
    PreDraw(pfChannel *chan, void *data)
    {
        static long stereoFlag = 0 ;

        if (stereoFlag)
          glDrawBuffer(GL_BACK_RIGHT);
        else    
          glDrawBuffer(GL_BACK_LEFT);
      
        stereoFlag = !stereoFlag;    

        .....
    }

Overlapping views

ex5: Clearing and drawing two partially overlapping channels.

    void
    PreDraw(void)
    {
        .....

        /* Clear the frame buffer of the background channel */
        chan->clear();

        /* Draw the background channel */
        pfDraw();

        /* Clear the frame buffer of the foreground channel */
        chan2->clear();

        /* Draw the foreground channel */
        pfDraw();
    }

Buffer Swapping

ex6: A buffer swapping function.

    void OpenWin(pfPipeWindow *pw)
    {
        .....

        pfGetPipe(0)->setSwapFunc(StereoSwap(pw));
        .....
    }

    pfPipeSwapFuncType StereoSwap(pfPipeWindow *pw)
    {
        pw->swapBuffers();
        return 0;         /* prevents warnings in compilation */
    }

Querying the system (for stereo)

ex7: One way to discover stereo capability (Note: this particular method occasionally reports a falsely positive response)

    void OpenWin(pfPipeWindow *pw)
    {
        int          Stereo = 1; /* Stereo-Mode, default is on */
        int          stereo_flag = 0;

        .....

        pw->query(PFQWIN_STEREO,&stereo_flag);
        if(stereo_flag==PFQFTR_FALSE)
        {
          cout << "Mono-Mode" << endl;
          // here might be a good place to reset the channel
          // viewing offsets since stereo isn't possible.
          {
            pfVec3 xyz, hpr;
            xyz.set(0.0f, 0.0f, 0.0f);
            hpr.set(0.0f, 0.0f, 0.0f);
            chan->setViewOffsets(xyz,hpr);
            chan2->setViewOffsets(xyz,hpr);
          }
          Stereo=0;
        } 
        else
          cout << "Stereo-Mode" << endl;

        .....
    }

Putting your monitor in stereo-mode

ex8: Setting the window attributes to allow for stereo.

    static int FBAttrs[]={PFFB_DOUBLEBUFFER,
                          PFFB_STEREO,
                          None};

    void
    InitPipe(void)
    {

        pfPipeWindow *pw;

        .....

        pw->setFBConfigAttrs(FBAttrs); /* set window attributes */

        pw->setConfigFunc(OpenWin);    /* configuration function */
        pw->config();                  /* call to configure */

        .....
    }

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