fix horizon clipping of atmosphere

[strangerintheq]

bug: using AtmosphereLayer with zoom and tilt will cause unnecessary clipping of image generated by SkyProgram

here is a bugfix

[AkeluX]

Thank you. We'll look into this issue and your fix.

@strikerM any thoughts on this?

[strikerM]

In my opinion, we should use the same method as WorldWindAndroid for handling the clipping of the sky atmosphere.
https://github.com/NASAWorldWind/WorldWindAndroid/blob/master/worldwind/src/main/java/gov/nasa/worldwind/WorldWindow.java#L1023

I think the new Camera implementation should fix this issue.

@pdavidc @balhar-jakub

[strangerintheq]

does this method can handle elevations?

[strikerM]

I'm not sure I understand the question.
The Sky Atmosphere doesn't "follow" the terrain.

[pdavidc]

@strikerM is right, the WorldWindAndroid method resolves this issue.

[strangerintheq]

Clipping is cool, but what about negative elevations? Is method handle situation With max tilt and zoom in area in pacific ocean?

[AkeluX]

Thank you for your inputs. We propose to continue the discussion in #105 as we won't take this pull request as is.