Feature: Add NavCubePlugin option to align with project/true North

[xeolabs]

• Published in: @xeokit/xeokit-sdk 2.4.0-alpha-20
• Run demo: https://xeokit.github.io/xeokit-sdk/examples/gizmos_NavCubePlugin_trueNorth.html
• Note that CDNs may still be caching old versions of xeokit for an undetermined time

Add an optional offset angle property "projectNorthOffsetAngle" to NavCubePlugin to align it with project North / true North.

As we rotate the NavCube, it calculates the eye, look, and 'up' at set on the Scene's camera. Conversely, when we interact with the Scene's camera, the NavCube calculates it's own camera's eye, look, and 'up' from the camera's matrix.

This solution works by rotating the eye->look direction vector according to projectNorthOffsetAngle, just before we transfer it from the Scene camera to the NavCube camera, or vice-versa.

By rotating the vector, we're able to avoid the disorientation problem we were having earlier from instead applying a yaw rotation to the camera. The problem with the yaw rotation was that it is rotating about the camera's local "upwards" axis, so that was causing the weird tumbling side effect.

Screencast.from.11.05.2023.21.05.05.webm

Usage

 import {Viewer, NavCubePlugin, XKTLoaderPlugin} from  "../dist/xeokit-sdk.es.js";

    const viewer = new Viewer({
        canvasId: "myCanvas"
    });

    viewer.camera.eye = [-3.933, 2.855, 27.018];
    viewer.camera.look = [4.400, 3.724, 8.899];
    viewer.camera.up = [-0.018, 0.999, 0.039];

    const xktLoader = new XKTLoaderPlugin(viewer);

    new NavCubePlugin(viewer, {
        canvasId: "myNavCubeCanvas",

        isProjectNorth: true,
        projectNorthOffsetAngle: -30.0 // Example value

    });

    const sceneModel = xktLoader.load({
        id: "myModel",
        src: "../assets/models/xkt/v10/glTF-Embedded/Duplex_A_20110505.glTFEmbedded.xkt", // Sets visual states of object in model
        edges: true
    });

Work remaining

When we click on the top or bottom of the cube, the scene camera loses the north-alignment. Will fix by rotating the 'up' vector that's used when setting the scene camera for upwards/downwards looking orientations. Will push what we've got so far now though, in @xeokit/xeokit-sdk 2.4.0-alpha-19.