Fix some math used by disableDepthDistance

[emackey]

Fixes #5501, fixes #5331, fixes #5621.

This closes 3 issues, but somehow still doesn't feel perfect. In particular, Number.POSITIVE_INFINITY tends to show through the globe very reliably now, whereas before it was spotty.

The original math error was along these lines:

    (z/w) < -1 || (z/w) > 1

This had been "simplified" by multiplying both sides by w, like so:

    z < -w || z > w

This simplification only works for positive values of w (the greater-than/less-than sense gets swapped for negative values of w).

/cc @bagnell @rahwang @tfili

[cesium-concierge]

@emackey thanks for the pull request!

I noticed that CHANGES.md has not been updated. If this change updates the Cesium API in any way, fixes a bug, or makes any non-trivial update, please add a bullet point to CHANGES.md and bump this pull request so we know it was updated. For more info, see the Pull Request Guidelines.

I am a bot who helps you make Cesium awesome! Thanks again.

[rahwang]

Amazing! Thank you, thank you @emackey ! Is there any chance we could get this merged ASAP so it can make it into the workshop code?

[emackey]

@rahwang Can you try copying this into your project prior to merge, for an additional test?

[rahwang]

Officially no more labels in the sky! You da man, @emackey!

[emackey]

Updated CHANGES.md. This is ready.

[bagnell]

Thanks @emackey! This looks good to me.

[thw0rted]

Will this be included in 1.37? It was a significant issue for us.

[mramato]

Will this be included in 1.37? It was a significant issue for us.

Yes, anything merged into the master branch is always available in the next release (which is almost always the first business day of the month). In this case, Sep 1st.