immersive2/src/controllers/functions/buildRig.ts

import {
    AxesViewer,
    Mesh,
    MeshBuilder,
    PhysicsAggregate,
    PhysicsMotionType,
    PhysicsShapeType,
    TransformNode,
    Vector3,
    WebXRDefaultExperience
} from "@babylonjs/core";

import {DefaultScene} from "../../defaultScene";

export function buildRig(xr: WebXRDefaultExperience): Mesh {
    const scene = DefaultScene.Scene;
    const rigMesh = MeshBuilder.CreateCylinder("platform", {diameter: .5, height: .01}, scene);
    rigMesh.setAbsolutePosition(new Vector3(0, .01, 5));
    const cameratransform = new TransformNode("cameraTransform", scene);
    cameratransform.parent = rigMesh;
    xr.baseExperience.onInitialXRPoseSetObservable.add(() => {
        xr.baseExperience.camera.parent = cameratransform;
        xr.baseExperience.camera.position = new Vector3(0, 0, 0);
        cameratransform.rotation.set(0, Math.PI, 0);
    });
    for (const cam of scene.cameras) {
        cam.parent = cameratransform;
        cam.position = new Vector3(0, 1.6, 0);  // Reset to local position above platform
    }
    scene.onActiveCameraChanged.add(() => {
        for (const cam of scene.cameras) {
            cam.parent = cameratransform;
            cam.position = new Vector3(0, 1.6, 0);  // Reset to local position above platform
        }
    });


    rigMesh.isPickable = false;
    const axis = new AxesViewer(scene, .25);
    axis.zAxis.rotation.y = Math.PI;
    rigMesh.lookAt(new Vector3(0, 0.01, 0));
    rigMesh.visibility = 1;

    // Only create physics aggregate if physics engine is available
    if (scene.getPhysicsEngine()) {
        const rigAggregate =
            new PhysicsAggregate(
                rigMesh,
                PhysicsShapeType.CYLINDER,
                {friction: 0, center: Vector3.Zero(), mass: 50, restitution: .01},
                scene);
        rigAggregate.body.setMotionType(PhysicsMotionType.DYNAMIC);
    } else {
        // Add physics aggregate once physics is initialized
        scene.onReadyObservable.addOnce(() => {
            if (scene.getPhysicsEngine()) {
                const rigAggregate =
                    new PhysicsAggregate(
                        rigMesh,
                        PhysicsShapeType.CYLINDER,
                        {friction: 0, center: Vector3.Zero(), mass: 50, restitution: .01},
                        scene);
                rigAggregate.body.setMotionType(PhysicsMotionType.DYNAMIC);
            }
        });
    }

    return rigMesh;
}