When using polygon to draw an arch, it will collapse.

[sunqlPeanut]

What happened?

1.I want to draw an arch that doesn't collapse.

Reproduction steps

...

Sandcastle example

https://sandcastle.cesium.com/#c=jZNRa9swEMe/yuEnBxI5bbouSd2wzHsYrHSFjUGp96DK11hMlowkJ7il372yrbAkTYptMLq73/90h++YksbCmuMGNVyDxA0kaHhVkD+tL0wD1tqJkpZyiToNBlepTCVrlaym8k6JeqWkk3d5CErLLUdDaJaFL6kEkLTAOaRB4nBYo7acUQGlF264zaFEPSqVcULnyZGvcmuAygxUZYW7OA2GTSavmUObFyDnqKlmeT3fFp5Qbd2Jygl50qr4hiuNaJZa0/p7lzZ86LQAo9mYjIdb6+Jsx9gNjKazU9j52D176PQUevEO/dwfvexfwKc+LR1yk5OtX57Czj/uZ/JhP9P+6Kx3Aft/83hLfwf+4Abuzs9bNxdzsLpCHy2oRc2p+D9WSihNkvvlrSf8XO6pvK9lD5Rfb5bJjxZ7dd/Xboma1y/Ns1LFbxUerNDgCoJhEBtbC1xsm/nCi1JpC5UWISGRxaIUrlwTPVbsH1rCjGnSN2gc7UrjjK+BZ9dHlhqYoMa4yFMlxC/+7PZtEUeOfycVimZcrn66NRa0brD8bHHTOQkhceTM40qrlHik+iDzGw

Environment

Browser:
CesiumJS Version:
Operating System:

[sunqlPeanut]

[ggetz]

Hi @sunqlPeanut,

The reason for this is detailed in this comment. I would recommend either revising the list of position such the arch is constructed of 3 coplanar polygons instead of one. Or perhaps using a glTF model if that suits your workflow.

Thanks!