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Details

Type: Bug
Resolution: Done
Priority: P2: Important
Fix Version/s: None
Affects Version/s: 5.7.0
Component/s: Qt3D
Labels:
None
Environment:
Ubuntu 16.04, Nvidia, Qt 5.7.0

Commits:
335246d0b6cf0498bf26a48b296ad44fab566c8f

Description

Changing the activeFrameGraph property in RenderSettings causes the application to crash. The crash appears to happen in RenderSettings::sceneChangeEvent where the line

m_activeFrameGraph = propertyChange->value().value<QNodePtr>()->id();

segfaults because the QNodeId holds a null pointer. I would be happy to investigate this further, but I was unable to figure out where this event is coming from and why the id is invalid.

I have attached an example project that illustrates this problem. When the switch in the upper left corner is pressed, the application crashes. The main.qml looks as follows:

import QtQuick 2.5
import QtQuick.Controls 1.4
import QtQuick.Window 2.2
import QtQuick.Scene3D 2.0
import Qt3D.Core 2.0
import Qt3D.Extras 2.0
import Qt3D.Logic 2.0
import Qt3D.Input 2.0
import Qt3D.Render 2.0

ApplicationWindow {
    id: root

    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    Scene3D {
        anchors.fill: parent
        aspects: ["render", "input", "logic"]
        Entity {
            components: [
                RenderSettings {
                    activeFrameGraph: switchBox.checked ? graph1 : graph2
                },
                InputSettings {
                    id: inputSettings
                }
            ]

            ForwardRenderer {
                id: graph1
                camera: Camera {
                    aspectRatio: root.width / root.height
                    position: Qt.vector3d(7.0, 7.0, 7.0)
                    viewCenter: Qt.vector3d(0, 0, 0)
                }
            }

            ForwardRenderer {
                id: graph2
                camera: Camera {
                    aspectRatio: root.width / root.height
                    position: Qt.vector3d(3.0, -7.0, 2.0)
                    viewCenter: Qt.vector3d(0, 0, 0)
                }
            }

            Entity {
                components: [
                    CuboidMesh {},
                    PhongMaterial{}
                ]
            }
        }
    }

    Switch {
        id: switchBox
    }
}

The following quote in the documentation indicates that the above example should work: "Of course, since this is a QML property binding, the active framegraph (or parts of it) can be changed on the fly at runtime." from https://doc.qt.io/qt-5/qt3drender-framegraph.html