Placing a prim in the real world
Anchor a prim to a real-world object that the runtime recognizes in the physical environment.
Overview
When the runtime detects real-world landmarks such as surfaces, images, and faces, it keeps tabs on them in case the app needs to refer to them later as data points for adding virtual content. To track a landmark, the runtime assigns an anchor and updates it to track the orientation and position of that landmark while it’s visible in the camera feed.
Use this schema to attach prims to anchors that the runtime can recognize and track in the physical environment. When you assign the prim an anchor type, the runtime places the prim on the first anchor of that type that it sees in the AR experience.
Place a prim on a surface, image, or face
The following cube requests that the runtime place it on the first real-world horizontal surface detected in the physical environment.
def Cube "PlaneAnchoredCube" (
prepend apiSchemas = [ "Preliminary_AnchoringAPI" ]
)
{
uniform token preliminary:anchoring:type = "plane"
uniform token preliminary:planeAnchoring:alignment = "horizontal"
...
}The cube defined in the following example sends a request to the runtime to place it at the real-world location of an image described by image.png.
def Cube "ImageAnchoredCube" (
prepend apiSchemas = [ "Preliminary_AnchoringAPI" ]
)
{
uniform token preliminary:anchoring:type = "image"
rel preliminary:imageAnchoring:referenceImage = <ImageReference>
...
def Preliminary_ReferenceImage "ImageReference"
{
uniform asset image = @image.png@
uniform double physicalWidth = 0.12
}
}
The following example instructs the runtime to place a cube at the real-word location of a detected face. In RealityKit, a face anchor centers its content at its origin, which is the detected face’s plane midpoint.
def Cube "FaceAnchoredCube" (
prepend apiSchemas = [ "Preliminary_AnchoringAPI" ]
)
{
uniform token preliminary:anchoring:type = "face"
...
}