Rotations Example#

Using rotated scatter items.

This example shows how to do the following:

  • Use item rotations

  • Use custom item meshes

  • Use range gradient to color the series

For more basic example about using Qt Data Visualization graphs, see Bars Example .

../_images/rotations-example.png

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.

Using Rotations#

In this example we want to orient the arrow items tangentially to the origin. This requires rotating them, which can be achieved by specifying rotation quaternion to each item:

yRotation = QQuaternion.fromAxisAndAngle(0.0f, 1.0f, 0.0f, horizontalAngle * radiansToDegrees)        zRotation = QQuaternion.fromAxisAndAngle(0.0f, 0.0f, 1.0f, verticalAngle * radiansToDegrees)
totalRotation = yRotation * zRotation        ptrToDataArray.setRotation(totalRotation)

Since the items need to be rotated along two axes, we define two rotation quaternions, one for Y-axis and one for Z-axis, and then multiply these together to get the total rotation, which we set to the data item.

Using Custom Item Meshes#

The narrow arrow mesh we use for magnetic field arrow items is not a standard mesh. Instead we supply our own narrowarrow.obj file which contains the object definition for the mesh in Wavefront obj format:

m_magneticField.setMesh(QAbstract3DSeries.MeshUserDefined)
m_magneticField.setUserDefinedMesh(QStringLiteral(":/mesh/narrowarrow.obj"))

Using Range Gradient#

Setting the color style to range gradient in a series means that the item is colored according to its relative Y-value on the visible Y-coordinate range. We want the arrows on the bottom part of the graph to be darker and gradually get lighter higher they are, so we define a range gradient with black color at the position 0.0 and white color at the position 1.0:

fieldGradient = QLinearGradient(0, 0, 16, 1024)
fieldGradient.setColorAt(0.0, Qt.black)
fieldGradient.setColorAt(1.0, Qt.white)
m_magneticField.setBaseGradient(fieldGradient)
m_magneticField.setColorStyle(Q3DTheme.ColorStyleRangeGradient)

Example Contents#

Example project @ code.qt.io