- Qt 6.4
- Qt Quick 3D Physics
- Qt Quick 3D Physics Examples and Tutorials
- Qt Quick 3D Physics - Cannon Example
- Qt Quick 3D Physics | Commercial or GPLv3

# Qt Quick 3D Physics - Cannon Example

Demonstrates how to spawn physical objects.

This example demonstrates how to create and delete physical objects on demand. The scene consists of a number of stacks of boxes. You can move around by using `WASD` and the mouse and shoot a ball by pressing `space`.

The scene is setup with the usual Qt Quick 3D objects like view, camera and light:

     PerspectiveCamera {
         id: camera
         position: Qt.vector3d(-4000, 5000, 10000)
         eulerRotation : Qt.vector3d(-20, -20, 0)
         clipFar: 500000
         clipNear: 100
     }
     DirectionalLight {
         eulerRotation: Qt.vector3d(-45, 45, 0)
         castsShadow: true
         brightness: 1
         shadowMapQuality: Light.ShadowMapQualityVeryHigh
         shadowFactor: 100
     }

We also add a static floor:

     StaticRigidBody {
         eulerRotation: Qt.vector3d(-90, 0, 0)
         collisionShapes: PlaneShape {}
         Model {
             source: "#Rectangle"
             scale: Qt.vector3d(2000, 2000, 0)
             materials: PrincipledMaterial {
                 baseColor: "green"
             }
             castsShadows: false
             receivesShadows: true
         }
     }

We create a Node we use as the spawner of objects and put inside our view:

     Node {
         id: shapeSpawner
         property var instancesBoxes: []
         property var instancesSpheres: []
         property int stackCount: 0

         function createStack(stackZ) {
             var size = 10;
             var extents = 400;

             for (var i = 0; i < size; i++) {
                 for (var j = 0; j < size-i; j++) {
                     var component = Qt.createComponent("box.qml");
                     let x = j*2 - size + i;
                     let y = i*2 + 1;
                     let z = -5*stackZ;
                     let center = Qt.vector3d(x, y, z).times(0.5*extents);
                     let box = component.createObject(shapeSpawner, {position: center, xyzExtents: extents});
                     instancesBoxes.push(box);

                     if (box === null) {
                         console.log("Error creating object");
                     }
                 }
             }
         }

         function createBall(position, forward) {
             var diameter = 600;
             var speed = 20000;
             var component = Qt.createComponent("sphere.qml");
             let sphere = component.createObject(shapeSpawner, {position: position, linearVelocity: forward.times(speed), sphereDiameter: diameter});
             instancesSpheres.push(sphere);

             if (sphere === null) {
                 console.log("Error creating object");
             }
         }

         function reset() {
             instancesSpheres.forEach(sphere => { sphere.destroy(); });
             instancesBoxes.forEach(boxes => { boxes.destroy(); });
             instancesSpheres = [];
             instancesBoxes = [];

             for (var stackI = 0; stackI < stackSlider.value; stackI++) {
                 shapeSpawner.createStack(stackI);
             }
         }
     }

We have three methods: `createStack` for creating a stack, `createBall` for creating a ball with velocity and `reset` for resetting the scene. The actual box and sphere that is spawn is stored in their own qml files (`box.qml` and `sphere.qml`).

Files:

- cannon/CMakeLists.txt
- cannon/Crosshair.qml
- cannon/box.qml
- cannon/cannon.pro
- cannon/main.cpp
- cannon/main.qml
- cannon/qml.qrc
- cannon/sphere.qml