平面检测

与网格检测类似，平面检测提供现实表面的平面估计。

各平面可带 wall、floor、table 等可选标签。

可使用预先捕获数据或实时重建，取决于系统实现。

支持

if (app.xr.planeDetection.supported) {
    // plane detection is supported
}

app.xr.on('start', () => {
    if (app.xr.planeDetection.available) {
        // plane detection is available
    }
});

访问

启动会话时添加功能标志：

app.xr.start(camera, pc.XRTYPE_AR, pc.XRSPACE_LOCALFLOOR, {
    planeDetection: true
});

平面异步添加和移除：

app.xr.planeDetection.on('add', (xrPlane) => {
    // a new XrPlane has been added

    xrPlane.once('remove', () => {
        // an XrPlane has been removed
    });
});

也可读取 XrPlane 列表：

const xrPlanes = app.xr.planeDetection.meshes;
for (let i = 0; i < xrPlanes.length; i++) {
    const xrPlane = xrPlanes[i];
}

网格

平面由 XrPlane 表示，会话期间可增删，数据也可变化。

读取世界空间位置和旋转：

entity.setPosition(xrPlane.getPosition());
entity.setRotation(xrPlane.getRotation());

局部点和朝向可构建可视网格，点列表表示多边形轮廓顶点。

xrPlane.orientation 表示垂直、水平或其他方向。

以下为每个平面构建网格并添加到场景根：

app.xr.planeDetection.on('add', (xrPlane) => {
    // geometry data
    const mesh = new pc.Mesh(app.graphicsDevice);
    mesh.clear(true, true); // ensure that mesh is created with dynamic buffers

    // create a list of vertices
    const vertices = new Float32Array((xrPlane.points.length + 1) * 3);

    // first point is always in the origin
    vertices[0] = 0;
    vertices[1] = 0;
    vertices[2] = 0;

    // create a list of indices
    const indices = new Uint32Array(xrPlane.points.length * 3);

    // construct a polygon where each edge is connected to the origin of a mesh
    for (let i = 0; i < xrPlane.points.length; i++) {
        vertices[i * 3 + 3 + 0] = xrPlane.points[i].x;
        vertices[i * 3 + 3 + 1] = xrPlane.points[i].y;
        vertices[i * 3 + 3 + 2] = xrPlane.points[i].z;
        indices[i * 3 + 0] = 0;
        indices[i * 3 + 1] = i + 1;
        indices[i * 3 + 2] = ((i + 1) % xrPlane.points.length) + 1;
    }

    mesh.setPositions(vertices); // set vertices
    mesh.setNormals(pc.calculateNormals(vertices, indices)); // calculate normals
    mesh.setIndices(indices); // set indices
    mesh.update(pc.PRIMITIVE_TRIANGLES); // update buffers

    const material = new pc.StandardMaterial();
    const meshInstance = new pc.MeshInstance(mesh, material);

    const entity = new pc.Entity(xrPlane.label);

    // add render component
    entity.addComponent('render', {
        meshInstances: [ meshInstance ]
    });

    // add entity to the scene root
    app.root.addChild(entity);

    // clean up after XrPlane is removed
    xrPlane.once('remove', () => {
        material.destroy();
        mesh.destroy();
        entity.destroy();
    });
});

语义标签

XrPlane.label 有助于识别现实对象类型。

例如 floor、wall、door、window、table、screen、global mesh、other 等。标签列表并非最终限制，平台可以返回其他标签。

变化

底层支持时，属性会在会话期间更新，可监听并同步网格：

xrPlane.on('change', () => {
    // points and/or label have been changed
});