global proc float[] nearestApproach(float $positionX, float $positionZ,float $tempPosX,
 float $tempPosZ, float $velocity, float $tempVelocity, float $directionX, 
float $directionZ, float $tempDirX, float $tempDirZ)
{
	float $dpx, $dpz, $dv;	
	float $time;
	$dpx = $positionX - $tempPosX;
	$dpz = $positionZ - $tempPosZ;
	$ddx = $directionX - $tempDirX;
	$ddz = $directionZ - $tempDirZ;
	$dv = ($velocity + $tempVelocity)/ 2.0;

	if((($ddx + $ddz) * $dv) < 0.0001)
	{
		$time = 0.5;
	}
	else
	{
		$time = -1.0 * ($dpx + $dpz) / (($ddx + $ddz) * $dv);
	}
	
	if($time > 0) // don't care if nearest approach happens in the past.

	// now calculate the distance of the nearest approach
	$dpx += $time * $dv * $ddx;
	$dpz += $time * $dv * $ddz;

	float $distance = sqrt(($dpx * $dpx) + ($dpz * $dpz));

	float $retVal[2];
	$retVal[0] = $time;
	$retVal[1] = $distance;
	return $retVal;

}