- Qt 5.15
- Qt 3D
- Qt 3D: Audio Visualizer Example
- Qt 5.15.2 Reference Documentation

# Qt 3D: Audio Visualizer Example

Demonstrates combining Qt 3D rendering and Qt Quick 2 elements.

Audio Visualizer demonstrates how to implement an application that combines the use of Qt 3D rendering with Qt Quick 2D elements. The example uses media player to play music and it visualizes the magnitude of the music as animated bars.

#### Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

#### Qt Quick 2D Implementation

The Qt Quick Implementation in `audio-visualizer-qml/main.qml` of the example uses `MediaPlayer` to play audio content.

     MediaPlayer {
         id: mediaPlayer
         autoPlay: true
         volume: 0.5
         source: "qrc:/music/tiltshifted_lost_neon_sun.mp3"

The player is controlled with the `playButton` and c{stopButton}. Based on the clicked buttons the `state` of the `mainview` changes.

The 3D content is rendered using the `Scene3D` type. The state of the Audio Visualizer is maintained in the `mainview`. It's passed on to the `visualizer` as it's needed for the bar animations.

     Scene3D {
         anchors.fill: parent

         Visualizer {
             id: visualizer
             animationState: mainview.state
             numberOfBars: 120
             barRotationTimeMs: 8160 // 68 ms per bar
         }
     }

#### Qt 3D Implementation

The 3D elements of the example are created in `audio-visualizer-qml/Visualizer.qml`. The camera is set to a fixed position to show the visualized bars from a correct angle.

     Camera {
         id: camera
         projectionType: CameraLens.PerspectiveProjection
         fieldOfView: 45
         aspectRatio: 1820 / 1080
         nearPlane: 0.1
         farPlane: 1000.0
         position: Qt.vector3d(0.014, 0.956, 2.178)
         upVector: Qt.vector3d(0.0, 1.0, 0.0)
         viewCenter: Qt.vector3d(0.0, 0.7, 0.0)
     }

A `NodeInstantiator` is used to create the bars that visualize the magnitude of the music.

     // Bars
     CuboidMesh {
         id: barMesh
         xExtent: 0.1
         yExtent: 0.1
         zExtent: 0.1
     }

     NodeInstantiator {
         id: collection
         property int maxCount: parent.numberOfBars
         model: maxCount

         delegate: BarEntity {
             id: cubicEntity
             entityMesh: barMesh
             rotationTimeMs: sceneRoot.barRotationTimeMs
             entityIndex: index
             entityCount: sceneRoot.numberOfBars
             entityAnimationsState: animationState
             magnitude: 0
         }
     }

The `visualizer` also contains an `Entity` to show the progress. This element has a curve shaped mesh and it's rotated on a level to show the progress based on the duration of the played track.

     // Progress
     Mesh {
         id: progressMesh
         source: "qrc:/meshes/progressbar.obj"
     }

     Transform {
         id: progressTransform
         property real defaultStartAngle: -90
         property real progressAngle: defaultStartAngle
         rotationY: progressAngle
     }

     Entity {
         property Material progressMaterial: PhongMaterial {
             ambient: "#80C342"
             diffuse: "black"
         }

         components: [progressMesh, progressMaterial, progressTransform]
     }

In `audio-visualizer-qml/BarEntity.qml` there are animations for rotating the bars and changing the bar color. The bars are rotated on a level following a ring form. At the same time the color of the bars is animated.

     QQ2.NumberAnimation {
         id: angleAnimation
         target: angleTransform
         property: "barAngle"
         duration: rotationTimeMs
         loops: QQ2.Animation.Infinite
         running: true
         from: startAngle
         to: 360 + startAngle
     }
     QQ2.SequentialAnimation on barColor {
         id: barColorAnimations
         running: false

         QQ2.ColorAnimation {
             from: lowColor
             to: highColor
             duration: animationDuration
         }

         QQ2.PauseAnimation {
             duration: animationDuration
         }

         QQ2.ColorAnimation {
             from: highColor
             to: lowColor
             duration: animationDuration
         }
     }

The magnitude of each bar is read from a separate .raw file that is based on the track being played. As the bars rotate around the ring the height is scaled to highlight currently played position. After a full round of rotation, a new value is fetched for the bar.

Example project @ code.qt.io