SceneTransforms.wgs84ToWindowCoordinates returns undefined for certain camera angles

[hpinkos]

Reported on the forum: https://groups.google.com/forum/?hl=en#!topic/cesium-dev/ALIPbA_LSqU

var viewer = new Cesium.Viewer('cesiumContainer');
viewer.camera.lookAt(Cesium.Cartesian3.fromDegrees(20.5, 54.7), 
new Cesium.Cartesian3(35000.0, -200000.0, 100000.0));
viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);
var scene = viewer.scene;
var ellipsoid = scene.globe.ellipsoid;
var position = Cesium.Cartesian3.fromDegrees(0.0, 0.0);
var handler = new Cesium.ScreenSpaceEventHandler(scene.canvas);
handler.setInputAction(function(movement) {
    console.log(Cesium.SceneTransforms.wgs84ToWindowCoordinates(scene, position));
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

[aneesha2890]

Hi ,
I saw this code that finds html coordinates from entity and place a div on that position
var scratch3dPosition = new Cesium.Cartesian3();
var scratch2dPosition = new Cesium.Cartesian2();

// Every animation frame, update the HTML element position from the entity.
viewer.clock.onTick.addEventListener(function(clock) {
var position3d;
var position2d;

// Not all entities have a position, need to check.
if (entity.position) {
    position3d = entity.position.getValue(clock.currentTime, scratch3dPosition);
}

// Moving entities don't have a position for every possible time, need to check.
if (position3d) {
    position2d = Cesium.SceneTransforms.wgs84ToWindowCoordinates(
        viewer.scene, position3d, scratch2dPosition);
}

// Having a position doesn't guarantee it's on screen, need to check.
if (position2d) {
    // Set the HTML position to match the entity's position.
    testElement.style.left = position2d.x + 'px';
    testElement.style.top = position2d.y + 'px';

    // Reveal HTML when entity comes on screen
    if (!isEntityVisible) {
        isEntityVisible = true;
        testElement.style.display = 'block';
    }
} else if (isEntityVisible) {
    // Hide HTML when entity goes off screen or loses its position.
    isEntityVisible = false;
    testElement.style.display = 'none';
}

});

here for me SceneTransforms is coming undefined inspite of having values in all the three arguments passed to it.
Can someone help here??