Make Scene.pick work for translucent polygons

[OmarShehata]

@bagnell I know picking translucent geometry was added in #4979 but there doesn't appear to be a way to pick translucent polygons.

Here's a Sandcastle. It logs the name of the polygon clicked to the console. It will always click through all the layers of polygons and pick the bottom most one.

The expected behavior is for Scene.pick to pick the topmost polygon when pickTranslucentDepth is true.

This came up on the forum. The forum post also describes this problem with the built in picker widget (the one that creates the green "focus" box when you click). I'm not sure if that also uses Scene.pick under the hood?

[cesium-concierge]

Congratulations on closing the issue! I found these Cesium forum links in the comments above:

https://groups.google.com/forum/#!msg/cesium-dev/OjXbgPv1wkM/SlEclUkxBwAJ

If this issue affects any of these threads, please post a comment like the following:

The issue at #7032 has just been closed and may resolve your issue. Look for the change in the next stable release of Cesium or get it now in the master branch on GitHub https://github.com/AnalyticalGraphicsInc/cesium.

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[bagnell]

The expected behavior is for Scene.pick to pick the topmost polygon when pickTranslucentDepth is true.

This was fixed but I just want to note that pickTranslucentDepth only applies when using pickPosition. By default the depth of translucent geometry is not returned; however, pick should always pick translucent geometry.