Sorry to disturb. I encountered two problems needed to be solved not long ago.
Question 1: If i have a geo-position(which is the coordinate origin of local coordinate frame) and a boundingVolume box of a glTF data in local coordinate frame which is X_east_Y_north_Z_up(coordinate origin is at the center of the bottom of glTF model), can you tell me how to calculate the boundingVolume region on the ellipsoid? Can you recommend any material to learn about this?
Question 2: Is it possible not to embed the glb to the b3dm where we just use an URI instead? Do you have some sample data like this?
You will need a way to convert meters to longitude/latitude extents. There is some sample code for doing this here: https://github.com/AnalyticalGraphicsInc/3d-tiles-tools/blob/master/samples-generator/lib/utility.js.
I’m pretty sure the region would be like:
west = longitude - metersToLongitude(x)
south = latitude - metersToLongitude(y)
east = longitude + metersToLongitude(x)
north = latitude + metersToLongitude(y)
minHeight = 0
maxHeight = z
For question 2, I think we’ve considered that before but never formally implemented it or included it in the spec. What use case would you have in mind?