90 degree North offset causing problems with Sun and Cartographic Polygon


Cesium and Google both have north direction in “top screen direction”.
This is the common way that makes sense.

However, in Unreal the north direction has 90° offset, pointing into the red X-Axis (in “right screen direction”). You can confirm this by importing the “Sun Position Calculator”-Plugin by Epic:
On its SunSky-Actor you have to set the NorthOffset to -90 to match the CesiumSunSky.

If we have setup your (Archvis) scene using Unreals north direction, we have to rotate the Cesium3DTileset-Actor to (0,0,90).
This causes problems with the CesiumSunSky-Actor and Cartographic Polygons not working correctly.

Can this be confirmed or am I wrong?

Thanks very much,

Yes, that sounds right. I have no idea why the Unreal SunSky chose to point the X axis North by default. Are you aware of other things in Unreal that follow this convention, or is it just the SunSky?

Trying to rotate the globe in the UE reference frame is likely to be a losing battle right now. We do intend to support this eventually, but right now it doesn’t work well. You might have more luck nesting your other scene elements inside an Actor or a sub-level instance with a rotation to make it match Cesium’s convention.

For sure it´s not only Unreals SunSky that has the main direction along the x-axis, it is Unreals general coordinate system. We can also see this for example with geometry imported from 3dsmax:
Objects orientated top screen in 3dsmax appear 90° rotated to the right screen direction in Unreal.

Sounds not like a big issue (attaching the models to a rotated actor in Unreal) but it is simply annoying that there are no general conventions about this and Epic did this dubious decision.