--

 bool

 getWorld2ScreenCoord( vpChannel   *channel,

                       vpTransform *xform,

                       float        *scrX,

                       float       *scrY ){

vuMatrixf world2screen;

vuVec4f point;

vuVec3d pos;

vuVec3d posTest1;

//

// Grab the Current View matrix

//

vuMatrix viewMat = channel->getViewMatrix();

//  

// Look at vector, set to +Y

//

vuVec3d  at;

at.set( 0.0, 1.0, 0.0 );

//

// make Look at vector point in direction of Look

//

viewMat.transformPoint( &at );

//  

// put Look at vector at eyepoint

//

at -= viewMat[ 3 ];

//  

// Next map xform's position to screen space

//

xform->getAbsolutePosition( &pos );

//  

// pos1 used to test whether xform is in front of observer

//

posTest1 = pos;

//

// put xform position vector at eyepoint

//

posTest1 -= viewMat[ 3 ];

//  

// only draw if xform is in front of observer

//

if ( at.dot( posTest1 ) > 0.0 ) {

//

// find center point of tracked xform in normalized screen coords

// screen coords get viewport and world to screen matrix

//

 int ox, oy, sx, sy;

channel->getVrChannel()->getViewport( &ox, &oy, &sx, &sy );

world2screen = channel->getVrChannel()->getWorldToScreenMatrix();

point.set( pos[0], pos[1], pos[2], 1.0f );

//  

// transform the points to clip space

//

world2screen.transform( &point );

//  

// divide by w

//

float fx = point.m_vec[ 0 ] / point.m_vec[ 3 ];

float fy = point.m_vec[ 1 ] / point.m_vec[ 3 ];

//  

// normalize to [0,1] range

//  

*scrX = ( fx + 1.0f ) / 2.0f;

&scrY = ( fy + 1.0f ) / 2.0f;

//  

// centerX and centerY are the normalized channel coordinates

//

return true;

}

return false;

}  // getWorld2ScreenCoord