GroundPolylineGeometry glitches on mobile (and others clamp to ground geometries doesn't display at all)

[Spec1alFx]

Original forum post with screenshot here.

I encountered graphical glitches with GroundPolylineGeometry on mobile when camera is quite near / far of this kind of polyline;
the problem it's consistent on every modern smartphone I tried on (Galaxy Note 9, Huawei P9 Lite, Wikio UFeel; iPhone 6), meanwhile on a Note 3 polyline is drawn under the terrain - but it's an old device, I don't think it's a big concern (*).

I'm able to reproduce the problem on every Sandcastle demo I tried;
with this one:

https://cesiumjs.org/Cesium/Build/Apps/Sandcastle/?src=Clamp%20to%20Terrain.html

I encountered another problem: a lot of geometries are not displayed at all on modern mobile devices. But there is already an open issue (#7273).

Please consider this two bugs related because today I can't use corridors as fallback on mobile.

*: I suppose that with a flag like Cesium.Entity.supportsPolylinesOnTerrain I can make things work also on older device switching to corridors if GroundPolylineGeometry are not supported;
it's a paradox but on my old Note 3 corridors are correctly rendered!

Thank you!

[hpinkos]

Thanks for the bug report @Spec1alFx! Could you please paste the results from http://webglreport.com/ from one of the devices that you're seeing this problem?

Also, what browser are you using on the smart phones?

[Spec1alFx]

Thank to you, Hannah.

I have attached screenshot for both WebGL 1 / WebGL 2 from my Note 9;
sorry but with plain text copy / paste the result is terrible.

Browsers: Chrome on Android smartphones, Safari on iPhone. I'm a traditionalist. :)

[likangning93]

Related: #6739 and #6735

[Spec1alFx]

D'oh! Sorry for opening a issue clone;
I made some searches but I miss them.

[hpinkos]

@Spec1alFx no worries! We have a hard time finding the right open issue sometimes too =)

I'm going to close this as a duplicate of #6735