How to calculate north and east vector for i3dm tile


After reading the 3D tiles specifications, im confused how to calculate the i3dm north and east vectors. Are the vectors local or global transformations?

could someone explain to me how the vectors are calculate?

Thank you,


Hello Ian, welcome to the forum. I’d be happy to help you with this, but let me first make sure that I understand your question.

Is it the case that you have some 3D Tiles with i3dm data, and you are trying to retrieve the east-north-up vectors for a particular instance of a model using CesiumJS? If so, is it your goal to then use those values in a CesiumJS application?

Is that correct, or are you asking something more general about the 3D Tiles specification for Instanced 3D Models?

It sounds like you already read the relevant portion of the 3D Tiles specification, but just in case, here it is: 3d-tiles/ at main · CesiumGS/3d-tiles · GitHub