ecmascript:
// REF: http://astronomy.swin.edu.au/pbourke/geometry/rotate/

function initialize () {
   visibility = 20;
   depth = 0;
   pos = (0,0,0);
   Browser.print ('Position output from ProximitySensor.');
}

function get_clock_hit (clock_msg) {
     run_script = true;
}

function get_depth ( position ) {

   pos = position;
   depth = position[1] - 30;   

}

function set_visibility( rotation ) {

 if (run_script) {

//z coordinate of the default viewpoint direction(0,0,-1)
   initZ = -1;  

   rX = rotation[0];  // x coordinate of the rotation
   rY = rotation[1];  // y coordinate of the rotation
   rZ = rotation[2];  // z coordinate of the rotation

   theta = rotation[3];  // angle of rotation in radians
	
Browser.print ('theta:' + theta);
     
   cosTheta = Math.cos(theta);
   sinTheta = Math.sin(theta);

Browser.print ('cosTheta:' + cosTheta + ' sinTheta:'+ sinTheta);


// calculate the y coordinate of the point after rotation
/* there are 8 other terms in the full conversion, but 6 are equal
to zero because of the choice of a starting point on the z-axis. The
other two are not calculated since all we need is the y coordinate
*/
   finalY = ((1 - cosTheta) * rY * rZ - rX * sinTheta) * initZ;

Browser.print ('final y:' + finalY);

//calculate the elevation/depression angle of the final point location

   elevation = Math.asin(finalY);

Browser.print ('elevation:' + elevation);

   directionFactor = 1 + 0.2 * (4 * elevation / Math.PI);
   depthAdjust = (60 + depth)/60
   depthFactor = Math.max(depthAdjust,0.05);

   visibility_changed =  60 * depthFactor * directionFactor; 
   Browser.print ('depth=' + depth + ', elevation=' + elevation + 
        ', visibility_changed=' + visibility_changed);
   run_script = false;
   
 }
}