How To Show 3D Model In QML's QtLocation

Question

I currently run an application in QML (Qt's Declarative Language) running on version 5.15. In the application I am using QtLocation with the mapboxgl plugin to show a map using MapBox layers and styles.

What I want to show is a 3D object inside QML's map, thus I can use MapBox's capabilities, routing, etc.

I have tried using Qt Quick 3D in the following code:

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.5
import QtPositioning 5.15
import QtLocation 5.15
import QtQuick.Layouts 1.3
import QtQuick3D 1.15

ApplicationWindow {
    color: "white"
    visibility: Window.FullScreen
    visible: true
    id: window
    width: Screen.width
    height: Screen.height

    Map {
        id: map
        anchors.fill: parent
        center: QtPositioning.coordinate(32.208574, 35.055456)

        zoomLevel: 16
        tilt: 40
        bearing: 260

        plugin: Plugin {
            id: myPlugin
            name: "mapboxgl"
            PluginParameter {
                name: "mapbox.access_token"
                value: "TOKEN"
            }

            PluginParameter {
                name: "mapboxgl.mapping.additional_style_urls";
                value: "mapbox://styles/mapbox/outdoors-v12"
            }

        }

        MapQuickItem {
            id: mapItem
            coordinate: QtPositioning.coordinate(32.208574, 35.055456) // Replace with your coordinates
            sourceItem:  Model {
                id: model3D
                source: "FinalBaseMesh.obj" // Replace with the path to your 3D model file
            }


        }
    }
}

However I got an error stated: 'Cannot assign object of type "Model" to property of type "QQuickItem*" as the former is neither the same as the latter nor a sub-class of it.'

I also tried importing Three.js using the following import statement: import "https://unpkg.com/three@0.126.0/build/three.min.js" as Three

And got a type error, most likely due to compatibility issues. I had tried to follow the MapBox tutorial on https://docs.mapbox.com/mapbox-gl-js/example/add-3d-model/

Moreover, I also tried using the now deprecated QtCanvas3D (taking the cellphone working example and trying to migrate it to Map) with the example code at Qt's git I changed the main.qml to the following:

/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtCanvas3D module of the Qt Toolkit.
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** $QT_BEGIN_LICENSE:BSD$
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** accordance with the commercial license agreement provided with the
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** information use the contact form at https://www.qt.io/contact-us.
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** BSD License Usage
** Alternatively, you may use this file under the terms of the BSD license
** as follows:
**
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** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
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****************************************************************************/

import QtQuick 2.15
import QtQuick.Window 2.15
import QtLocation 5.15
import QtPositioning 5.15

Window {
    property int initialWidth: 800
    property int initialHeight: 600
    id: mainView
    width: initialWidth
    height: initialHeight
    visible: true
    title: "Interactive Mobile Phone Demo"
    color: "black"

    //! [0]
    Item {
        id: textureSource
        layer.enabled: true
        layer.smooth: true
        layer.textureMirroring: ShaderEffectSource.NoMirroring
        //! [0]
        anchors.centerIn: parent
        // The dimensions of the texture source item determine the actual OpenGL texture dimensions.
        // We want a fairly large texture, so that even the smallest text we use renders nicely.
        width: 512
        height: 1024
        // Hide texture source behind the canvas normally, so you can't interact with it.
        // It would also be possible to set visible property to false instead, but if the item
        // is hidden, some things don't update correctly. For example, the Flickable doesn't update
        // its content if it is not visible.
        z: -2
        // Specify transform to make the visual representation of the item match the size and
        // orientation of the ui presented in Canvas. If the window initial dimensions,
        // textureSource dimensions, or phone mesh dimensions or position are changed,
        // scaling needs to be adjusted accordingly.
        //! [2]
        transform: [
            Scale {
                origin.y: textureSource.height / 2
                origin.x: textureSource.width / 2
                yScale: 0.5 * mainView.height / mainView.initialHeight
                xScale: 0.5 * mainView.height / mainView.initialHeight
            }
        ]
        opacity: 0.0
        //! [2]

        // CellphoneApp implements the UI of the phone
        CellphoneApp {
            id: cellphoneApp
            anchors.fill: parent
            backgroundColor: "black"
            textColor: "white"
            onLocked: canvas3d.state = "running"
        }
    }



    // CellphoneCanvas displays the rotating phone and the color selector
    CellphoneCanvas {
        id: canvas3d
        anchors.fill:parent
        textureSource: textureSource
        onRotationStopped: {
            cellphoneApp.resetLockTimer()
            // Bring the UI to the foreground so that it can be interacted with
            textureSource.z = 1
        }
        onRotationStarted: {
            // Hide the texture source behind canvas to ensure UI cannot be
            // interacted while the phone is rotating.
            textureSource.z = -1
        }
    }

    Map {
        width: 200
        height: 200
        center: QtPositioning.coordinate(0,0)


        plugin: Plugin {
            id: myPlugin
            name: "mapboxgl"
            PluginParameter {
                name: "mapbox.access_token"
                value: "TOKEN"
            }

            PluginParameter {
                name: "mapboxgl.mapping.additional_style_urls";
                value: "mapbox://styles/mapbox/outdoors-v12"
            }

        }

        MapQuickItem {
            // Set the map item properties
            coordinate: QtPositioning.coordinate(0,0)
            //anchorPoint.x: dot.width * 0.5
            //anchorPoint.y: dot.height

            // Use the Canvas3D for rendering
            sourceItem: canvas3d
        }
    }

    ColorSelector {
        anchors.right: parent.right
        anchors.top: parent.top
        width: parent.width / 16

        onSelectedColorChanged: canvas3d.caseColor = selectedColor
    }

    // FPS display, initially hidden, clicking will show it
    FpsDisplay {
        anchors.left: parent.left
        anchors.top: parent.top
        width: 32
        height: 64
        //fps: canvas3d.fps
    }
}

Is there anyone that had any success?

I was trying to show a 3D object inside a QML map using two possible solutions - QtQuick3D and Three.js, however was not capable of seeing the model in the application.

Answer 1

The mapboxgl plugin you have access to does not support 3d models. That means you are left with rendering your model "by yourself" through the QtQuick Scenegraph using an additional Map{} (layer) on top of the mapboxgl Map {} element. However, as QtLocation does not offer you any way to do so, you have to subclass QDeclarativeGeoMapItemBase and do the rendering yourself. I have seen this done but afaik there is no example on github.