GlobeAnnotation doesn't stay on top

[incubus]

Hi,

I am putting UserFacingIcons onto the map. I set their always on top attribute to true and it works fine. I then added a GlobeAnnotation beside each icon with some details about the icon and it also set their on top attribute to true. What I am seeing is the text falling behind the terrain when I change the tilt of the view.

Why is it that the setAlwaysOnTop call on the GlobeAnnotation appears to have no effect?

Regards,

John.

[dcollins]

John, Would you please post a screenshot of this behavior? That would go a long way towards helping us diagnose this issue.

Thanks,
Dave

[incubus]

Hi Dave, thanks for the reply.

I've attached two screenshots. The first one shows the camera directly above the annotation and it is visible. The second has the earth with a slight tilt and as you can see it starts to become obscured by the terrain. Eventually, as I tilt the earth more the annotation completely disappears behind the terrain.

Regards,

John.

[dcollins]

John,

That's exactly what I needed to see. Thank you very much. The behavior you're seeing is a difference between how WWIcon and Annotation interpret their alwaysOnTop property. Here are two bullet points outlining the difference:

• WWIcon interprets alwaysOnTop as indicating that the object is sorted in front of other objects, and should not be depth tested against other objects in the scene.
• Annotation interprets alwaysOnTop as indicating that the object is sorted in front of other objects, but should be depth tested against other objects in the scene.

This difference causes Annotation to appear in front of other OrderedRenderables, but incorrectly appears behind the terrain as though alwaysOnTop was never set. This is likely a bug. I'll create an issue in the World Wind bug base mentioned on http://goworldwind.org.

In the meantime, I'd recommend that you investigate whether it's possible to use PointPlacemark to replace your usage of Annotation. PointPlacemark was designed as a replacement for WWIcon and in some cases can also be used to replace Annotation.

Thanks,
Dave

[incubus]

Hi Dave,

thanks for looking into this. For my purpose just now the PointPlacemark can be used as an alternative.

What would happen if the globe annotation was to correctly use the always on top attribute and was to overlap another component with the same attribute set. Would they 'fight' for the top spot?

Regards,

John.

[dcollins]

John, Here are two bullet points outlining how Annotation would behave if it correctly interpreted the alwaysOnTop attribute:

• Annotations with alwaysOnTop set to true would appear on top of terrain, surface imagery, and surface objects.
• Annotations overlapping another object with alwaysOnTop set to true would appear in the order defined by the layer list. The object last in the layer list would be drawn on top.

Does that help clarify?

Thanks,
Dave

[incubus]

Dave, this answers my question perfectly.

Thank you for your assistance.

John.