ImageryLayer crash when using imagery provider rectangle option

[hpinkos]

Reported on the forum: https://groups.google.com/d/msg/cesium-dev/wMdmusP1Fu4/Jl_Uk7uABQAJ

It looks like ImageryLayers is trying to get an imagery tile that's outside the bounds of the imagery provider rectangle

var provider = new Cesium.WebMapServiceImageryProvider({ 
    url : ' http://ows.terrestris.de/osm/service?', 
    layers : 'OSM-WMS', 
    rectangle : Cesium.Rectangle.fromDegrees(149.0625, -36.5625, 154.6875, -30.93758), 
    minimumLevel : 6, 
}); 

var widget = new Cesium.CesiumWidget('cesiumContainer', {
    imageryProvider: provider
}); 
widget.imageryLayers.addImageryProvider(provider); 

[erikmaarten]

Looked through the ImageryLayer.js code, and (like @hpinkos said above) the problem appears when no intersection is found between imagery provider rectangle and imagery rectangle. Rectangle.simpleIntersection returns undefined if no intersection was found. Since there is no check for this case, I'm guessing it's not supposed to be a valid scenario.
@mramato Is this something you can comment on or have a look at?

[mramato]

@shunter or @kring would know for sure, but I'm guessing that we should check for undefined and simply continue the loop in that case (which should cover both usages in ImageryLayer.js).

[erikmaarten]

@mramato I did try that and ended up with a globe with a small rectangle of imagery looking OK, the rest of the globe had the pixels from the edges of that rectangle smeared out in each direction. Is that to be expected when providing a rectangle option to the Cesium.WebMapServiceImageryProvider constructor?

[mramato]

Is that to be expected when providing a rectangle option to the Cesium.WebMapServiceImageryProvider constructor?

If it is the base layer, than yes. We always stretch the outer pixels of the base layer to take up the whole screen. If you don't make it the base layer, then it should only take up the specified rectangle.

[erikmaarten]

Thanks @mramato. I'll submit a PR for this. Just to make sure, when stretching the base layer, is it supposed to look like this? The rectangle itself looks fine, but there seem to be gaps in the stretched base layer. It looks the pixels are stretched to the north pole, and to the west but only to (what looks like) the anti-meridian. The rectangle is around Sydney.

[mramato]

Normally I think it stretches in all directions, so that does look a little weird, but if there is a problem it's probably unrelated to the layer and instead to the stretching. As long as it looks correct when it's not the base layer, I think we're okay (but I'll let someone who knows more about this area of the code review the PR). Thanks.

[mramato]

I also just realized the sample code in the original post is a little odd, it adds the provider twice. Here's one that adds it as a non-base layer:

var provider = new Cesium.WebMapServiceImageryProvider({ 
    url : ' http://ows.terrestris.de/osm/service?', 
    layers : 'OSM-WMS', 
    rectangle : Cesium.Rectangle.fromDegrees(149.0625, -36.5625, 154.6875, -30.93758), 
    minimumLevel : 6, 
}); 

var widget = new Cesium.CesiumWidget('cesiumContainer'); 
var layer = widget.imageryLayers.addImageryProvider(provider);