Qt Quick 3D Physics - Simple Example▲

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This example gives an introductory overview of the basic Quick 3D Physics features by going through the code of a simple example. Note that this introduction assumes a familiarity with the Qt Quick 3D module.

Setup▲

The whole example is contained and set up in the main.qml file. Let's first look at the object that creates the physical world. This node is called DynamicsWorld:

 
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DynamicsWorld {
    running: true
}

We set the gravity property to point downwards in the y-direction with a magnitude that matches the gravity on earth. Note that all physical properties are unit-less so the magnitude could be -981 instead if we scaled the scene accordingly. It is possible to (un)pause the simulation by setting running to false.

Scene▲

Let's have a look at the scene.

 
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View3D {
    id: viewport
    anchors.fill: parent

    environment: SceneEnvironment {
        clearColor: "#d6dbdf"
        backgroundMode: SceneEnvironment.Color
    }

    PerspectiveCamera {
        position: Qt.vector3d(-200, 100, 500)
        eulerRotation: Qt.vector3d(-20, -20, 0)
        clipFar: 5000
        clipNear: 1
    }

    DirectionalLight {
        eulerRotation.x: -45
        eulerRotation.y: 45
        castsShadow: true
        brightness: 1
        shadowFactor: 100
    }

    StaticRigidBody {
        position: Qt.vector3d(0, -100, 0)
        eulerRotation: Qt.vector3d(-90, 0, 0)
        collisionShapes: PlaneShape {}
        Model {
            source: "#Rectangle"
            scale: Qt.vector3d(10, 10, 10)
            materials: DefaultMaterial {
                diffuseColor: "green"
            }
            castsShadows: false
            receivesShadows: true
        }
    }

    DynamicRigidBody {
        position: Qt.vector3d(-100, 100, 0)
        collisionShapes: BoxShape {
            id: boxShape
        }
        Model {
            source: "#Cube"
            materials: PrincipledMaterial {
                baseColor: "yellow"
            }
        }
    }

    DynamicRigidBody {
        position: Qt.vector3d(0, 100, 0)
        collisionShapes: SphereShape {
            id: sphereShape
        }
        Model {
            source: "#Sphere"
            materials: PrincipledMaterial {
                baseColor: "blue"
            }
        }
    }

    DynamicRigidBody {
        position: Qt.vector3d(75, 200, 0)
        collisionShapes: CapsuleShape {
            id: capsuleShape
        }

        Model {
            geometry: CapsuleGeometry {}
            materials: PrincipledMaterial {
                baseColor: "red"
            }
        }
    }
}

Our scene is just a View3D since we want to draw our physical objects. It contains a PerspectiveCamera and a DirectionalLight for rendering, but more importantly it contains a StaticRigidBody and three DynamicRigidBody nodes. In physics, a rigid body is a non-deformable, solid body with uniform density. We have two types of rigid bodies available; StaticRigidBody and DynamicRigidBody. A StaticRigidBody is a QML node which contains a static (immovable) rigid body. It is technically possible to move the body but it will incur a performance penalty. A DynamicRigidBody on the other hand is used for objects that can move. A DynamicRigidBody has a isKinematic property, when it is set to true the rigid body will not be influenced by external forces and can be controlled from scripts and animations. For instance a football would not be kinematic but an elevator or a moving platform typically would. This also means that if you update the position property of the football it would not move to that position whereas the elevator would.

To be able to interact with other physical objects the collisionShapes property needs to be set. The collisionShapes property is a list that can contain one or more shapes and will act as one rigid unit combined. You can position and rotate these shapes in relation to each other. Note that plane, triangle mesh and heightmap shapes only work with dynamic bodies if the body is kinematic.

Shapes▲

Our scene contains four physical objects (plane, box, ball, capsule). We will go through them one at a time.

Plane▲

 
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StaticRigidBody {
    position: Qt.vector3d(0, -100, 0)
    eulerRotation: Qt.vector3d(-90, 0, 0)
    collisionShapes: PlaneShape {}
    Model {
        source: "#Rectangle"
        scale: Qt.vector3d(10, 10, 10)
        materials: DefaultMaterial {
            diffuseColor: "green"
        }
        castsShadows: false
        receivesShadows: true
    }
}

We create a plane by making a StaticRigidBody node. In this node we set the collisionShapes property to contain a PlaneShape. Planes divide space into "above" and "below" them. Everything "below" the plane will collide with it and be pushed above it. The Plane lies on the YZ