angleToTrueNorth is null for Navisworks translated model

Question

When translating a Navisworks model to SVF, the value for angleToTrueNorth from model.getData().metadata['custom values'].angleToTrueNorth is not available. Where else can I find it?

Answer 1

Unfortunately, the angleToTrueNorth is Revit only, i.e., translating RVT directly with Model Derivative API, as far as I know.

model.getData().metadata['custom values'].angleToTrueNorth

However, if your NWC/NWD model was exported from RVT using shared coordinates after last April, then we could calculate that from the nwModelToWorldTransform transform in the manifest.

"derivatives": [
{
    "name": "racbasicsampleproject.nwc",
    "hasThumbnail": "true",
    "status": "success",
    "progress": "complete",
    "properties": {
        "Document Information": {
            "Navisworks File Creator": "nwexportrevit",
            "nwModelToWorldTransform": [
                0.7986355100472902,
                0.6018150231520518,
                0,
                -0.6018150231520518,
                0.7986355100472902,
                0,
                0,
                0,
                1,
                -65.03805139774867,
                -61.70701987942478,
                0
            ]
        },

        ///...

Here is how we can calculate the angle to true north from the transform:

let model = viewer.getAllModels()[0];
let doc = model.getDocumentNode().getDocument();
let docRoot = doc.getRoot();
let docInfo = docRoot.children[0].data.properties['Document Information'];

let angle = THREE.Math.radToDeg(Math.acos( docInfo.nwModelToWorldTransform[0] )) //!<<< ref: https://en.wikipedia.org/wiki/Transformation_matrix#Affine_transformations

let angelToTrueNorth = -1.0 * angle; //!<<< The angelToTrueNorth is clockwise, but the angle in math is counterclockwise

So, using the above nwModelToWorldTransform transform for example, the calculated angelToTrueNorth will be:

let angle = THREE.Math.radToDeg(Math.acos( 0.7986355100472902 )); //<<< 37°

let angelToTrueNorth = -1.0 * 37; //!<<< -37° = 323°