How to add 3D elements into the Hololens 2 field of view

Question

I'm trying to build a Remote Assistance solution using the Hololens 2 for university, i already set up the MRTK WebRTC example with Unity. Now i want to add the functionality of the desktop counterpart being able to add annotations in the field of view of the Hololens to support the remote guidance, but i have no idea how to achieve that. I was considering the Azure Spatial Anchors, but i haven't found a good example of adding 3D elements in the remote field of view of the Hololens from a 2D desktop environment. Also i'm not sure if the Spatial Anchors is the right framework, as they are mostly for persistent markers in the AR environment, and i'm rather looking for a temporary visual indicator. Did anyone already work on such a solution and can give me a few frameworks/hints where to start?

Answer 1

To find the actual world location of a point from a 2D image, you can refer this answer: https://stackoverflow.com/a/63225342/11502506

In short, cameraToWorldMatrix and projectionMatrix transforms define for each pixel a ray in 3D space representing the path taken by the photons that produced the pixel. But anything along a certain ray will show up on the same pixel. So to find the actual world location of a point, you'll need either use Physics.Raycast method to calculate the impact point in world space where the ray hit the SpatialMapping.