vector.project returns infiniy code example

Example: vector.project returns infiniy

var screenvector = new THREE.Vector3();
var position = new THREE.Vector3();
position = convertLatLontoVec3(lat, lng).multiplyScalar(radius);
//convertLatLontoVec3(returns new THREE.Vector3(x, y, z);)
screenvector.copy(position);
//till here during debugging i can find the values of position.x, .y, .z 
screenvector.project(camera); //But once this step is executed all the values are becoming infintiy. I don't understand why is it happening.