Ellipsoid-centered

This is the "native" reference frame of Cesium.


Handedness	Right
Units	Meters
Origin	Center of the ellipsoid (Earth)
Orientation	+X passes through the intersection of the equator and prime meridian (0 degrees latitude, 0 degrees longitude) +Y passes through the intersection of the equator and +90 degrees longitude (0 degrees latitude, 90 degrees longitude) +Z is up through the North Pole

Georeferenced

A reference frame defined by the ACesiumGeoreference actor.


Handedness	Right
Units	Meters
Origin	The origin defined by the `ACesiumGeoreference::OriginPlacement` and possibly `OriginLongitude`, `OriginLatitude`, and `OriginHeight` properties.
Orientation	If `ACesiumGeoreference::AlignTilesetUpWithZ` is true: +X points East at the origin +Y points North at the origin +Z is in the direction of the ellipsoid surface normal at the origin (up) If `ACesiumGeoreference::AlignTilesetUpWithZ` is false: Same as Ellipsoid-centered above.

Cesium Tileset

The reference frame of a Cesium 3D Tiles tileset, as defined by the tileset.json. Usually, tilesets are georeferenced and this reference frame is identical to the Ellipsoid-centered frame described above, but this is not strictly required by 3D Tiles. A non-georeferenced model of a building, for example, may have an origin at the center of the building and axes aligned with the principal sides of the building.


Handedness	Right
Units	Meters
Origin	Specified by tileset.json, often the center of the Earth.
Orientation	Specified by tileset.json, often ECEF.

Unreal Tileset

The same as the Cesium Tileset, but expressed in Unreal Engine terms: the coordinates are in centimeters (multiplied by 100.0) and left-handed (have an inverted Y component) relative to Cesium Tileset coordinates.

Please note that the transformation from Unreal Tileset coordinates to Unreal Absolute/Relative World (below) is affected by the ACesium3DTileset Actor's Location and Orientation properties. However, these should almost always be set to identity.


Handedness	Left
Units	Centimeters
Origin	Specified by tileset.json, often the center of the Earth.
Orientation	Specified by tileset.json, often ECEF.

Unreal Absolute World

Vectors and matrices in Unreal Engine are expressed using single-precision floating-point numbers. In order to maintain precision, these coordinate values must remain relatively small. To support this, the Unreal floating world origin can be moved by setting the OriginLocation property of UWorld. Coordinates that are said to be in the "Unreal Absolute World" reference frame are expressed relative to the absolute origin (0,0,0) and are not affected by the value of the OriginLocation property.


Handedness	Left
Units	Centimeters
Origin	No fixed meaning.
Orientation	No fixed meaning.

Unreal Relative World

This reference frame has the same orientation as "Unreal Absolute World", but is offset from it by the UWorld's OriginLocation. Coordinates are expressed relative to the floating origin.


Handedness	Left
Units	Centimeters
Origin	No fixed meaning.
Orientation	No fixed meaning.