WebXR Meshing API Level 1

1. Introduction

1.1. Terminology

1.2. Application flow

2. Initialization

2.1. XRMeshQuality

enum XRMeshQuality {
   "low",
   "medium",
   "high"
};

XRMeshQuality defines the quality of the mesh. A higher quality means that the mesh will be finer but also more resource intensive. It is up to the UA to define the quality level.

2.2. XRWorldMeshFeature

The "worldmesh" feature is used to request world meshing.

dictionary XRWorldMeshFeature: XRFeatureInit {
    XRMeshQuality quality = "medium";
    double width = 10.0;
    double height = 10.0;
    double breadth = 10.0;
};

The width, height and breadth attributes define the distance, in meters, of the width, height and breadth of the area around the observer that should be meshed. The quality attribute defines the UA dependent quality of the mesh.

let xrSession;

navigator.xr.requestSession("immersive-ar", {
                            requiredFeature: {
                                name: "XRWorldMeshFeature",
                                quality: "medium"}}).then((session) => {
    xrSession = session;
});

should the world mesh follow the observer or should it stay relative to the original position or should it be configurable?

should the world mesh have an XRSpace?

2.3. XRNearMeshFeature

The "nearmesh" feature is used to request meshing near the observer. It is UA dependent what the scanned area for the near mesh is but it MUST not overlap with the world mesh.

dictionary XRNearMeshFeature: XRFeatureInit {
    XRMeshQuality quality = "medium";
};

The quality attribute defines the UA dependent quality of the mesh.

let xrSession;

navigator.xr.requestSession("immersive-vr", {
                            requiredFeature: {
                                name: "XRNearMeshFeature",
                                quality: "low"}}).then((session) => {
    xrSession = session;
});

should the near mesh have an XRSpace?

3. Frame Loop

3.1. XRMesh structures

dictionary XRMeshBlock {
    required Float32Array vertices;
    required Uint16Array indices;
    Float32Array normals;
};

A XRMeshBlock contains the geometry data of a single mesh instance.

vertices contains a buffer with points in 3D space. Each point consists of 3 floats.

Each value in indices points to an offset into a point inside vertices and defines the corner of a triangle. The set of triangles creates a polygon mesh. NOTE: the offset of each point is found by taking the index value and multiplying by 3.

XRMeshBlock can contain an optional normals which defines a buffer with the normal of each vertex. The size of normals must be the same as vertices.

is normals needed? If so, should it be requested during initialisation?

interface XRNearMesh {
    readonly setlike<XRMeshBlock>;
};

interface XRWorldMesh {
    readonly maplike<DOMString, XRMeshBlock>;
};

dictionary XRMetadata {
    XRWorldMesh worldMesh;
    XRNearMesh nearMesh;
};

The worldMesh attribute contains updates to the world mesh. If any key in the dictionary was a previously provided provided XRWorldMesh this new value must replace the previous XRMeshBlock. If the value of a new world XRMeshBlock contains no vertices, the existing XRMeshBlock must be deleted.

The nearMesh attribute contains a new near mesh which will replace the previous near mesh (if any). If nearMesh contains no new XRMeshBlock object, there is no near mesh.

3.2. XRFrame

partial interface XRFrame {
    readonly attribute XRMetadata metaData;
};

Each XRFrame contains a metaData attribute with new or updated world or near mesh data.

should the mesh data persist per browser session or per xr session?

4. Security and Privacy Considerations

The WebXR Meshing API is a powerful feature with that carries significant privacy risks. A UA MUST ask permission from the user during session creation before meshing data is returned to the page.

An inline session must NOT have access to mesh data.

Additionally, mesh data MUST be constructed from the geometry of the real world. It MUST not reveal writing, colors, pictures or other visual content.

clarify this section