QtQuick Qt Quick Examples - Shader Effects

This example demonstrates a couple of visual effects that you can perform with shaders in Qt Quick. It applies five different effects on a text and a couple of images. For more information, visit Important Concepts In Qt Quick - Graphical Effects

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.

The ShaderEffect type typically operates on other types, using a ShaderEffectSource:

ShaderEffectSource {
    id: theSource
    sourceItem: theItem
}

In the above snippet, theItem is the ID of a complex QML object in the file.

ShaderEffects can use this ShaderEffectSource as a texture in their fragment shader:

fragmentShader:
    "uniform lowp float qt_Opacity;" +
    "uniform highp float amplitude;" +
    "uniform highp float frequency;" +
    "uniform highp float time;" +
    "uniform sampler2D source;" +
    "varying highp vec2 qt_TexCoord0;" +
    "void main() {" +
    "    highp vec2 p = sin(time + frequency * qt_TexCoord0);" +
    "    gl_FragColor = texture2D(source, qt_TexCoord0 + amplitude * vec2(p.y, -p.x)) * qt_Opacity;" +
    "}"

You can use any custom property on the ShaderEffect in your shader. This makes animated shader code very easy:

property variant source: theSource
property real bend: 0
property real minimize: 0
property real side: genieSlider.value
SequentialAnimation on bend {
    loops: Animation.Infinite
    NumberAnimation { to: 1; duration: 700; easing.type: Easing.InOutSine }
    PauseAnimation { duration: 1600 }
    NumberAnimation { to: 0; duration: 700; easing.type: Easing.InOutSine }
    PauseAnimation { duration: 1000 }
}
SequentialAnimation on minimize {
    loops: Animation.Infinite
    PauseAnimation { duration: 300 }
    NumberAnimation { to: 1; duration: 700; easing.type: Easing.InOutSine }
    PauseAnimation { duration: 1000 }
    NumberAnimation { to: 0; duration: 700; easing.type: Easing.InOutSine }
    PauseAnimation { duration: 1300 }
}

ShaderEffects can also have a custom vertext shader. Setting the mesh property on ShaderEffect provides more vertices for you to manipulate, enabling more effects.

mesh: Qt.size(10, 10)
vertexShader: "
    uniform highp mat4 qt_Matrix;
    uniform highp float bend;
    uniform highp float minimize;
    uniform highp float side;
    uniform highp float width;
    uniform highp float height;
    attribute highp vec4 qt_Vertex;
    attribute highp vec2 qt_MultiTexCoord0;
    varying highp vec2 qt_TexCoord0;
    void main() {
        qt_TexCoord0 = qt_MultiTexCoord0;
        highp vec4 pos = qt_Vertex;
        pos.y = mix(qt_Vertex.y, height, minimize);
        highp float t = pos.y / height;
        t = (3. - 2. * t) * t * t;
        pos.x = mix(qt_Vertex.x, side * width, t * bend);
        gl_Position = qt_Matrix * pos;
    }"

Files:

  • shadereffects/shadereffects.qml
  • shadereffects/content/Slider.qml
  • shadereffects/main.cpp
  • shadereffects/shadereffects.pro
  • shadereffects/shadereffects.qmlproject
  • shadereffects/shadereffects.qrc