A fatal bug about depth test！

[abigstupidbear]

What happened?

After 1.136，I find a bug about billboard or text.

When you move the Earth, billboards are not hidden by the Earth.
Especially when viewed from a downward angle, you will notice that the billboard is still visible on the opposite side of the Earth.

already show ，but should be hidden！！

Reproduction steps

1. open https://sandcastle.cesium.com/?id=billboards
2. rotate the earth
   3.Especially in certain scenarios, it can significantly affect the display effect
   ...

Sandcastle example

https://sandcastle.cesium.com/?id=billboards

Environment

Browser: chrome 1.132
CesiumJS Version:1.136
Operating System:win 11

[abigstupidbear]

[mzschwartz5]

Hi @abigstupidbear,

I believe this is a result of some slightly-inaccurate math in the BillboardCollectionFS.glsl shader. This PR should fix the issue, but it was held up by some oddities with other ellipsoids.

@ggetz Maybe it's worth just merging the PR anyway even if it causes some slight issues with the Mars ellipsoid? I can get the PR up to date if you agree.

[abigstupidbear]

@mzschwartz5
thanks!
Could you tell me roughly when this bug will be fixed？
Is it the next version or unknown？

[mzschwartz5]

@abigstupidbear It's unlikely it will make it into the next version, which releases next Monday, but perhaps the version after that, if I'm correct about the root cause here.

[abigstupidbear]

@mzschwartz5
Thanks again, and we hope this issue can be resolved quickly!

[mzschwartz5]

@abigstupidbear This is build of sandcastle that contains the fix I referred to above. Could you test out your case there and confirm if it addresses the issues you saw?

[abigstupidbear]

@mzschwartz5 Great, no issues were found after testing！Thanks！