qt-creator/share/qtcreator/qml/qmlpuppet/mockfiles/AutoScaleHelper.qml

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import QtQuick 2.0
import QtQuick3D 1.0
import MouseArea3D 1.0

Node {
    id: overlayNode

    property View3D view3D
    property Node target: parent
    property bool autoScale: true

    // Read-only
    property real relativeScale: 1

    onSceneTransformChanged: updateScale()
    onAutoScaleChanged: updateScale()
    Connections {
        target: view3D.camera
        onSceneTransformChanged: updateScale()
    }

    function getScale(baseScale)
    {
        return Qt.vector3d(baseScale.x * relativeScale, baseScale.y * relativeScale,
                           baseScale.z * relativeScale);
    }

    function updateScale()
    {
        if (!autoScale) {
            target.scale = Qt.vector3d(1, 1, 1);
        } else {
            // Calculate the distance independent scale by first mapping the targets position to
            // the view. We then measure up a distance on the view (100px) that we use as an
            // "anchor" distance. Map the two positions back to the target node, and measure the
            // distance between them now, in the 3D scene. The difference of the two distances,
            // view and scene, will tell us what the distance independent scale should be.
            var posInView1 = view3D.mapFrom3DScene(scenePosition);
            var posInView2 = Qt.vector3d(posInView1.x + 100, posInView1.y, posInView1.z);

            var rayPos1 = view3D.mapTo3DScene(Qt.vector3d(posInView2.x, posInView2.y, 0));
            var rayPos2 = view3D.mapTo3DScene(Qt.vector3d(posInView2.x, posInView2.y, 10));

            var planeNormal = view3D.camera.forward;
            var rayHitPos = helper.rayIntersectsPlane(rayPos1, rayPos2, scenePosition,
                                                      planeNormal);
            relativeScale = scenePosition.minus(rayHitPos).length() / 100;
        }
    }

    MouseArea3D {
        id: helper
        view3D: overlayNode.view3D
    }
}