HoloLens Features and Concepts Introduction
Captures some features of Microsoft HoloLens.
Coordinate System Concepts
| Name | Description |
|---|---|
| Stationary frame of reference | For world-locked content in seated-scale experience - keep the object stable related to the world, while respect changes to the user’s head position and head orientation - an app creates 1 stationary frame of reference on startup and use it throughout the app’s lifetime, such as the world origin and world coordinate system in Unity engine- hologram may drift when users walk beyond 5 meters because the system determines distances between various points in the real-world are shorter or longer than the system previously believed (while the hologram’s coordinate keeps the same) - optimizes for stability near the user |
| Attached frame of reference | For body-locked content in orientation-only experiences - moves with the user as they walk around, with a fixed heading defined when the app first creates the frame - the only coordinate system which can be used to render holograms when the headset can’t figure out where it is in the world |
| Stage frame of reference | For standing-scale experience - defines a stage origin, a spatial coordinate system centered at the user’s chosen floor position and forward orientation where they intend to use the device - holograms with Y=0 appears on the floor - optimizes for stability near their origins |
| Stage bound | For room-scale experience - a single fixed coordinate system within which to place floor-relative content |
| Spatial anchor | For world-scale experience - represents an important point in the world that the system should keep track of over time - automatically adjust its position as device learns about the world to ensure that it stays precisely where it was placed relative to the real-world - has a coordinate system, placed holograms with positioning to its spatial anchor could maintain stability - optimizes for stability near their origins - could be saved in and located from anchor store with a string key as the reference. holograms associated to this spatial anchor could also be stored in local’s storage - supports sharing among devices and platforms with Azure Spatial Anchors service |
Scene Understanding vs Spatial Mapping
- tradeoff of maximal accuracy and latency to structure and simplicity.
| ~ | Scene Understanding | Spatial Mapping |
|---|---|---|
| Efficiency | higher level processing as it should provide you with a superset of functionality | the lowest-latency possible and mesh triangles that only you will want to access |
| Range | unlimited, provides all scanned spatial mapping data | limited, data are in a limited size cached ‘bubble’ around the user |
| Placement | SceneQuads infers which areas of the quad that were not scanned and invalidate areas, allowing placement not limited to scanned areas |
- place object in spatial surface - a surface cannot be used for placement if it has not been scanned |
| Occlusion | - support requesting data from spatial mapping from generated mesh - provides “best of both worlds” scenario |
provide occlusion in highly dynamic scenes |
| Physics | watertight meshes decompose space with semantics - ensures physics ray casts always hit - allows for simpler generation of nav meshes for indoor |
perform many raycasts within a small area and to use the aggregate results to derive a more reliable understanding of the surface since the surface is complex |
| Navigation | simplifying the floor structure, makes dynamic nav-mesh generation in 3d engines such as Unity are attainable | - NavMesh cannot be used because spatial mapping surfaces are not known until the application starts- spatial mapping system won’t provide information about surfaces very far away |
| Visualization | requesting unlimited number of surfaces from scene understanding’s version spatial mapping mesh, allowing capturing mesh representations for large space | ~ |