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Qt Quick 3D Physics - Compound Shapes Example

Demonstrates using complex collision shapes.

This example demonstrates how to use more than one collision shape to create complex objects for collision detection. The scene consists of a green static plane and a series of links connected to each other. At the beginning, the simulation is disabled. After some time or when the user press the space key, the simulation will start. An animation will start that causes the leftmost and rightmost links to move horizontally back and forth.

Setup

As usual we need to add our PhysicsWorld:

 PhysicsWorld {
     id: physicsWorld
     enableCCD: true
     maximumTimestep: 20
     scene: viewport.scene
 }

We do the usual setup where we have an environment, camera and lights:

 environment: SceneEnvironment {
     antialiasingMode: SceneEnvironment.MSAA
     backgroundMode: SceneEnvironment.Color
     clearColor: "lightblue"
 }

 focus: true

 PerspectiveCamera {
     id: camera
     position: Qt.vector3d(0, 900, 1500)
     eulerRotation: Qt.vector3d(-10, 0, 0)
     clipFar: 15500
     clipNear: 1
 }

 DirectionalLight {
     eulerRotation.x: -45
     eulerRotation.y: 45
     castsShadow: true
     brightness: 1.5
     shadowFactor: 15
     shadowFilter: 10
     shadowMapFar: 100
     shadowBias: -0.01
     shadowMapQuality: Light.ShadowMapQualityVeryHigh
 }

Physical objects

We have our regular static plane:

 StaticRigidBody {
     position: Qt.vector3d(0, -100, 0)
     eulerRotation: Qt.vector3d(-90, 0, 0)
     collisionShapes: PlaneShape {}
     Model {
         source: "#Rectangle"
         scale: Qt.vector3d(500, 500, 1)
         materials: DefaultMaterial {
             diffuseColor: "green"
         }
         castsShadows: false
         receivesShadows: true
     }
 }

Then we make instances of our links.

 MeshLink {
     id: leftLink
     isKinematic: true
     property vector3d startPos: Qt.vector3d(-6 * viewport.ringDistance,
                                             viewport.ringY,
                                             0)
     property vector3d startRot: Qt.vector3d(90, 0, 0)
     kinematicPosition: startPos
     position: startPos
     kinematicEulerRotation: startRot
     eulerRotation: startRot
     color: "red"
 }

 CapsuleLink {
     position: Qt.vector3d(-5 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(90, 0, 0)
 }

 MeshLink {
     position: Qt.vector3d(-4 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(90, 0, 0)
 }

 MeshLink {
     position: Qt.vector3d(-3 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(0, 90, 0)
 }

 MeshLink {
     position: Qt.vector3d(-2 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(90, 0, 0)
 }

 MeshLink {
     position: Qt.vector3d(-1 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(0, 90, 0)
 }

 CapsuleLink {
     position: Qt.vector3d(0, viewport.ringY, 0)
 }

 MeshLink {
     position: Qt.vector3d(1 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(0, 90, 0)
 }

 MeshLink {
     position: Qt.vector3d(2 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(90, 0, 0)
 }

 MeshLink {
     position: Qt.vector3d(3 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(0, 90, 0)
 }

 MeshLink {
     position: Qt.vector3d(4 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(90, 0, 0)
 }

 CapsuleLink {
     position: Qt.vector3d(5 * viewport.ringDistance, viewport.ringY, 0)
     eulerRotation: Qt.vector3d(90, 0, 0)
 }

 MeshLink {
     id: rightLink
     isKinematic: true
     property vector3d startPos: Qt.vector3d(6 * viewport.ringDistance,
                                             viewport.ringY,
                                             0)
     property vector3d startRot: Qt.vector3d(90, 0, 0)
     kinematicPosition: startPos
     position: startPos
     kinematicEulerRotation: startRot
     eulerRotation: startRot
     color: "red"
 }

The first link which is on the left has its isKinematic property set to true so that we can control it via animation. Since it is a kinematic object we need to set the kinematicPosition and kinematicRotation properties. We animate it by animating the kinematicPosition property. The other links are instanced with some spacing between them.

To get a smooth animation that follows the physical simulation exactly we use an AnimationController which we connect to the onFrameDone signal on the PhysicsWorld. This way, if there were to be any frame drops slowing down the simulation the animation will slow down accordingly. We use a SequentialAnimation with four NumberAnimation to move the leftmost and rightmost rings back and forth. This is the QML code for the animation:

 Connections {
     target: physicsWorld
     property real totalAnimationTime: 12000
     function onFrameDone(timeStep) {
         let progressStep = timeStep / totalAnimationTime
         animationController.progress += progressStep
         if (animationController.progress >= 1) {
             animationController.completeToEnd()
             animationController.reload()
             animationController.progress = 0
         }
     }
 }

 AnimationController {
     id: animationController
     animation: SequentialAnimation {
         NumberAnimation {
             target: leftLink
             property: "kinematicPosition.x"
             to: 3 * viewport.ringDistance
             from: -6 * viewport.ringDistance
             easing.type: Easing.InOutCubic
             duration: 1000
         }
         NumberAnimation {
             target: leftLink
             property: "kinematicPosition.x"
             from: 3 * viewport.ringDistance
             to: -6 * viewport.ringDistance
             easing.type: Easing.InOutCubic
             duration: 1000
         }
         NumberAnimation {
             target: rightLink
             property: "kinematicPosition.x"
             to: -3 * viewport.ringDistance
             from: 6 * viewport.ringDistance
             easing.type: Easing.InOutCubic
             duration: 1000
         }
         NumberAnimation {
             target: rightLink
             property: "kinematicPosition.x"
             from: -3 * viewport.ringDistance
             to: 6 * viewport.ringDistance
             easing.type: Easing.InOutCubic
             duration: 1000
         }
     }
 }

The interesting part is what is happening inside the Mesh and Capsule Links files. Let's take a look at each one of them.

 DynamicRigidBody {
     scale: Qt.vector3d(100, 100, 100)
     property color color: "white"
     PrincipledMaterial {
         id: _material
         baseColor: color
         metalness: 1.0
         roughness: 0.5
     }

     Model {
         source: "meshes/ring.mesh"
         materials: [_material]
     }

     collisionShapes: [
         ConvexMeshShape {
             source: "meshes/segmentedRing_001.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_002.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_003.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_004.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_005.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_006.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_007.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_008.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_009.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_010.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_011.mesh"
         },
         ConvexMeshShape {
             source: "meshes/segmentedRing_012.mesh"
         }
     ]
 }

The Mesh Link is a Dynamic Rigid Body with a model and a material. The model loads the mesh from a mesh file. We also have a list of collision shapes that together are combined and form a compound shape for collision detection. Each shape is a Convex Mesh shape which loads the mesh from a source file. A convex shape is basically a shape where the line between any two points within the shape is always inside the shape.

If we take a closer look when the debug mode is enabled, this is how the collision shapes form the compound collision shape:

 DynamicRigidBody {
     property real len: 170
     property real w: 17
     PrincipledMaterial {
         id: material3
         baseColor: "yellow"
         metalness: 1.0
         roughness: 0.5
     }
     Node {
         opacity: 1
         Model {
             materials: material3
             source: "#Cylinder"
             scale: Qt.vector3d(w / 100, len / 100, w / 100)
             eulerRotation.z: 90
             y: -len / 2
         }
         Model {
             materials: material3
             source: "#Cylinder"
             scale: Qt.vector3d(w / 100, len / 100, w / 100)
             eulerRotation.z: 90
             y: len / 2
         }
         Model {
             materials: material3
             source: "#Cylinder"
             scale: Qt.vector3d(w / 100, len / 100, w / 100)
             x: len / 2
         }
         Model {
             materials: material3
             source: "#Cylinder"
             scale: Qt.vector3d(w / 100, len / 100, w / 100)
             x: -len / 2
         }
         Model {
             materials: material3
             source: "#Sphere"
             scale: Qt.vector3d(w / 100, w / 100, w / 100)
             x: -len / 2
             y: -len / 2
         }
         Model {
             materials: material3
             source: "#Sphere"
             scale: Qt.vector3d(w / 100, w / 100, w / 100)
             x: -len / 2
             y: len / 2
         }
         Model {
             materials: material3
             source: "#Sphere"
             scale: Qt.vector3d(w / 100, w / 100, w / 100)
             x: len / 2
             y: -len / 2
         }
         Model {
             materials: material3
             source: "#Sphere"
             scale: Qt.vector3d(w / 100, w / 100, w / 100)
             x: len / 2
             y: len / 2
         }
     }
     collisionShapes: [
         CapsuleShape {
             y: -len / 2
             height: len
             diameter: w
         },
         CapsuleShape {
             y: len / 2
             height: len
             diameter: w
         },
         CapsuleShape {
             x: -len / 2
             eulerRotation.z: 90
             height: len
             diameter: w
         },
         CapsuleShape {
             x: len / 2
             eulerRotation.z: 90
             height: len
             diameter: w
         }
     ]
 }

The Capsule Link is a Dynamic Rigid Body with some models that share the same material. This link is formed from several cylinders and spheres. Like the Mesh Link we have a list of collision shapes. This time each shape is a Capsule Shape.

If we take a closer look when the debug mode is enabled, this is how the collision shapes form the compound collision shape.

Files:

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