About bounding volume defined by oriented Box

[Frédéric Trastour]

Hi All,

I need a little clarification about oriended box in TileSet definition.

Specs ( https://github.com/AnalyticalGraphicsInc/3d-tiles/blob/master/schema/boundingVolume.schema.json ) says :

 "box" : {
    "type" : "array",
    "description" : "An array of 12 numbers that define an oriented bounding box in WGS84 coordinates.
                    The first three elements define the x, y, and z values for the center of the box.
                    The next three elements (with indices 3, 4, and 5) define the x axis direction and length.
                    The next three elements (indices 6, 7, and 8) define the y axis direction and length.
                    The last three elements (indices 9, 10, and 11) define the z axis direction and length.",
    "items" : {
       "type" : "number"
     },
    "minItems" : 12,
    "maxItems" : 12
 },

I'm wondering what WGS84 coordinates does exactly mean :

    - Geographic/WGS84  : X & Y are Lon/Lat in radians and Z is a value in meters,

    - ECEF/WGS84  :  X, Y and Z are ECEF coordinates in meters.

    - something else ?

Does anyone here can clarify ?

Thanks in advance,

KR,

Fred.

[Frédéric Trastour]

Hi,

after looking on how  3D TileSets are loaded and interpreted in Cesium, I think that Box coordinates have to be ECEF (Cartesian) coordinates.

As I tile my input dataset using cartographic rectangles, corresponding oriented boxes in ECEF system are not easy to compute (and are probably not really boxes).

I will try to tile in geographic coordinates and the use the region tag in tileset.json.

Br,

Fred.

[Patrick Cozzi]

Hi Frédéric,

To confirm, yes ECEF and WGS84 coordinates are the same.  For more on WGS84, see http://earth-info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf

I agree that using the region property sounds like the best approach for you.

Patrick

[Frédéric Trastour]

Hi Patick,

thanks for your clarification.

I now use regions and it works fine, I was able to display my first 3D city few days ago :

> 700.000 buildings - B3DM tiles are generated on the fly.

3D Tiles is great.

Kr,

Fred.

[Patrick Cozzi]

Fred - awesome news, it looks great!  Cool project.  Do you have a link to a demo or more info about it?

Thanks,

Patrick

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