Forge APS Viewer - Revit Color Scheme - How to get room color from 2D Viewer

Question

We are trying to retrieve the Room colors (based on Views with Revit Color Scheme) from Sheets viewed in the 2D Viewer:

Color Scheme in Revit

For this purpose I retrieve all the rooms and get their materials:

const tree = model.getInstanceTree();
const frags = model.getFragmentList();

const getRoomsId = new Promise((resolve, reject) => {
    obj.model.search('Rooms', function (dbIds) {
        dbIds.some(dbId => {
            if (tree.getNodeName(dbId) === 'Rooms') {
                resolve(dbId)
                return true
            }
        })
    })
})

getRoomsId.then(function (roomsId) {
    tree.enumNodeChildren(roomsId,
      function (childId) {
        tree.enumNodeFragments(childId, function (fragid) {
            const material = frags.getMaterial(fragid);
            console.log('Room: ', childId, ' / ', tree.getNodeName(childId), ' Fragment: ', fragid, ' Material: ', material.uuid)
        })
       }
    )
})

Unfortunately they all seem to have the same material as shown in the log below, so I have no idea where the colors are coming from:

tree.enumNodeChildren(childId)

doesn't retrieve anything so I wonder if somehow it is using an overlay to display the colors.

Any help is very much appreciated.

Answer 1

Instead of using Material the 2D Viewer uses Vertex colors.

    const mesh = frags.getVizmesh(fragId);
    const vbr = new Autodesk.Viewing.Private.VertexBufferReader(mesh.geometry, viewer.impl.use2dInstancing);

    var vertexCount = vbr.vcount;

    for (var i = 0; i < vertexCount; i++) {
        // Each vertex knows its related dbId
        var dbId = vbr.getDbIdAt(i);
        // sign extend the upper byte to get back negative numbers (since per-vertex ids are clamped from 32 bit to 24 bit)
        dbId = dbId << 8 >> 8;
        var color = vbr.getColorAt(i)
        color = color >>> 0     // Signed to Unsigned 32
        color &= 0x00FFFFFF     // Getting rid of opacity
    }

Note: The color is stored as GBR instead of RGB