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Diffstat (limited to 'examples/datavisualization/qmlspectrogram/doc/src/qmlspectrogram.qdoc')
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1 files changed, 42 insertions, 4 deletions
diff --git a/examples/datavisualization/qmlspectrogram/doc/src/qmlspectrogram.qdoc b/examples/datavisualization/qmlspectrogram/doc/src/qmlspectrogram.qdoc index 6ebba93b..ee0018e3 100644 --- a/examples/datavisualization/qmlspectrogram/doc/src/qmlspectrogram.qdoc +++ b/examples/datavisualization/qmlspectrogram/doc/src/qmlspectrogram.qdoc @@ -22,20 +22,58 @@ \ingroup qtdatavisualization_examples \brief Showing spectrogram graph in a QML application. - The Qt Quick 2 surface example demonstrates how to show a polar and cartesian spectrograms + The Qt Quick 2 Spectrogram example demonstrates how to show a polar and cartesian spectrograms and how to utilize orthographic projection to show them in 2D. - TODO!!! - \image qmlspectrogram-example.png + Spectrogram is simply a surface graph with a range gradient used to emphasize the different + values. Typically spectrograms are shown with two dimensional surfaces, which we simulate + with a top down orthographic view of the graph. In this example, the default input handler + is enabled, so you can also rotate the graph to see how it looks in three dimensions. In + a real application you may want to disable the default input handling if you wish to show + only the two dimensional graph. See \l{Qt Quick 2 Custom Input Example} for guidelines on + customizing input handling. + The focus in this example is on showing how to display spectrograms, so the basic functionality is not explained. For more detailed QML example documentation, see \l{Qt Quick 2 Scatter Example}. - \section1 TODO + \section1 Creating a spectrogram + + To create a 2D spectrogram, we define a Surface3D item: \snippet qmlspectrogram/qml/qmlspectrogram/main.qml 0 + The key properties for enabling the 2D effect are + \l{AbstractGraph3D::orthoProjection}{orthoProjection} and + \l{Camera3D::cameraPreset}{scene.activeCamera.cameraPreset}. We remove the perspective by + enabling orthographic projection for the graph, and then we eliminate the Y-dimension by + viewing the graph directly from above: + + \snippet qmlspectrogram/qml/qmlspectrogram/main.qml 1 + + Since this viewpoint causes the horizontal axis grid to be mostly obscured by the surface, + we also specify that the horizontal grid should be drawn on top of the graph: + + \snippet qmlspectrogram/qml/qmlspectrogram/main.qml 2 + + \section1 Polar spectrogram + + Depending on the data, it is sometimes more natural to use a polar graph instead of a cartesian + one. Qt Data Visualization supports this via \l{AbstractGraph3D::polar}{polar} property. + In this example we provide a button to switch between polar and cartesian modes: + + \snippet qmlspectrogram/qml/qmlspectrogram/main.qml 3 + + In the polar mode, the X-axis is converted into the angular polar axis, and the Z-axis is + converted into the radial polar axis. The surface points are recalculated according to new axes. + + The radial axis labels are drawn outside the graph by default, but in this example we want to + draw them right next to the 0 degree angular axis inside the graph, so we define only a tiny + offset for them: + + \snippet qmlspectrogram/qml/qmlspectrogram/main.qml 4 + \section1 Example contents */ |