Distorted Box Entity in iOS

[OmarShehata]

This Sandcastle example looks like a perfectly fine box on desktop:

var viewer = new Cesium.Viewer('cesiumContainer');

var redBox = viewer.entities.add({
    name : 'Red box with black outline',
    position: Cesium.Cartesian3.fromDegrees(-107.0, 40.0, 0.0),
    box : {
        dimensions : new Cesium.Cartesian3(0.2,0.2,1),
        material : Cesium.Color.RED,
        outline : true,
        outlineColor : Cesium.Color.BLACK
    }
});

viewer.zoomTo(redBox);

On iOS, the vertices seem to be displaced?

Forum post tested on iOS 11. I just tested on iOS 10.2.1

[mramato]

I can confirm this is still an issue in iOS 12.0 on an iPhone 7, but someone should check iPad as well to see if it's software/vs hardware issue.

[OmarShehata]

I can reproduce this on the iPad Pro in the office, with iOS 12.2. This forum post may be the same issue. Here's another Sandcastle that, on desktop draws 20 lines:

Sandcastle

But on the iPad, only 4 lines are drawn. I haven't tried this myself but there's a suggestion in the forum thread there to modify the function in https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Shaders/Builtin/Functions/translateRelativeToEye.glsl to add:

if (length(highDifference) == 0.0) highDifference = vec3(0);

Before the highDifference is returned to fix this issue.

[jjhembd]

Resolved by #11788

[onsummer]

Reason here: https://bugs.webkit.org/show_bug.cgi?id=237434