Camera.zoomIn doesn't work when viewport width < height

[hpinkos]

Reported on the forum: https://groups.google.com/forum/?hl=en#!topic/cesium-dev/5Urmnt2xwqE

The following example works correctly when the canvas width is greater than the canvas height, but not when the width is less than the height:

var viewer = new Cesium.Viewer('cesiumContainer', {sceneMode : Cesium.SceneMode.SCENE2D});
var scene = viewer.scene;
var clock = viewer.clock;

viewer.camera.maximumZoomFactor = 0;
var currentMagnitude = viewer.camera.getMagnitude();
console.log('currentMagnitude - ' + currentMagnitude);
viewer.camera.zoomIn((currentMagnitude - 1000));
console.log('NewMagnitude - '+ viewer.camera.getMagnitude());

[cfickler]

This could probably be shortened, but it solves the issue:

function zoom2D(camera, amount) {
var frustum = camera.frustum;

            if (!defined(frustum.left) || !defined(frustum.right) || !defined(frustum.top) || !defined(frustum.bottom)) {
        throw new DeveloperError('The camera frustum is expected to be orthographic for 2D camera control.');
    }
    
    //************************************************************************************************************************************
    // Calculate the frustum based on the height and width of the map        
    //************************************************************************************************************************************        
    if((Math.abs(frustum.top) + Math.abs(frustum.bottom)) > (Math.abs(frustum.left) + Math.abs(frustum.right))) {        	
    	amount = amount * 0.5;
        var newTop = frustum.top - amount;
        var newBottom = frustum.bottom + amount;

        var maxBottom = camera._maxCoord.x;
        if (camera._scene.mapMode2D === MapMode2D.ROTATE) {
            maxBottom *= camera.maximumZoomFactor;
        }

        if (newBottom > maxBottom) {
            newRight = maxBottom;
            newTop = -maxBottom;
        }

        if (newTop <= newBottom) {
            newTop = 1.0;
            newBottom = -1.0;
        }
        
    	var ratio = frustum.right / frustum.top;
        frustum.top = newTop;
        frustum.bottom = newBottom;
        frustum.right = frustum.top * ratio;
        frustum.left = -frustum.right;
    } else {
    	amount = amount * 0.5;
        var newRight = frustum.right - amount;
        var newLeft = frustum.left + amount;

        var maxRight = camera._maxCoord.x;
        if (camera._scene.mapMode2D === MapMode2D.ROTATE) {
            maxRight *= camera.maximumZoomFactor;
        }

        if (newRight > maxRight) {
            newRight = maxRight;
            newLeft = -maxRight;
        }

        if (newRight <= newLeft) {
            newRight = 1.0;
            newLeft = -1.0;
        }
    	var ratio = frustum.top / frustum.right;
        frustum.right = newRight;
        frustum.left = newLeft;
        frustum.top = frustum.right * ratio;
        frustum.bottom = -frustum.top;
    }
    //******************************************************************************************************************************************
}

[hpinkos]

Thanks @cfickler! Would you be interested in opening a pull request with that fix? You can see instructions in our contributing documentation: https://github.com/AnalyticalGraphicsInc/cesium/blob/master/CONTRIBUTING.md#opening-a-pull-request