cesium for unreal 坐标参考框架_cesium for unreal坐标系

Reference Frames 参考框架

This is an inventory of the most important reference frames used in Cesium for Unreal.

在Cesium for Unreal 中用到的重要的坐标参考框架清单。

Ellipsoid-centered 地心坐标系

This is the “native” reference frame of Cesium.

Cesium最原始的坐标参考框架。

Georeferenced 地理参考系 NEU

A reference frame defined by the ACesiumGeoreference actor.

ACesiumGeoreference actor 定义的自身的局部坐标参考系。

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.

tileset.json 文件定义的 Cesium 3D Tiles 坐标参考系。通常在要求不严格的情况下，tilesets的坐标参考框架和 WGS84 地心坐标系一致。例外的情况是，一栋没有地理参考的建筑物模型，它的原点位于模型的中心，坐标轴与主要的侧面对齐。

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.

Unreal Tileset 与 Cesium Tileset 相同，只不过是在 Unreal Engine 的术语。坐标系单位厘米，左手系。

注意从Unreal Tileset 坐标到 Unreal 绝对/相对坐标系的转换，它往往会与ACesium3DTileset Actor的地理参考有关。然而通常情况下，它们总是会设置成相同的。

Unreal Absolute World (Unreal 绝对坐标系)

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 absolute 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.

UE4 中的向量和矩阵使用单精度浮点类型。为了保证精度，坐标数值必须保持相对小。为了达到这个目的，UE4的绝对世界原点可以通过 UWorld的属性OriginLocation设置。 这里的世界坐标系是相对与坐标原点(0,0,0) 而言的，不被这个OriginLocation属性值所影响。

Unreal Relative World (Unreal 相对坐标系)

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.

这个坐标框架的坐标轴与 Unreal 绝对坐标系的坐标轴一致，原点是浮动的，是相对于UWorld的 OriginLocation动态偏移的。

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