add video with "entity/polygon", the video flip horizontal

[xuanyuanq...@gmail.com]

var viewer = new Cesium.Viewer('cesiumContainer', {
showRenderLoopErrors : false,
shouldAnimate : true
});

var videoElement = document.getElementById('trailer');

var entity = viewer.entities.add({
polygon: {
hierarchy: Cesium.Cartesian3.fromDegreesArrayHeights(110,30,10000, 110,40,10000, 120,40,10000, 120,30,10000),
height: 10000,
material: videoElement,
perPositionHeight: true,
}
});

question:
I want to use "entities" add video with "polygon", when I set the parameter "perPositionHeight" true, the video is normal,
but when I set the parameter "perPositionHeight" false, the video is flip horizontal, how to solve the problem? Thank you.

[Omar Shehata]

Thanks for reporting this. I think this is a bug. I opened a GitHub issue for it, so we'll see if anyone has any solutions: 

https://github.com/AnalyticalGraphicsInc/cesium/issues/7185