In addition to being controlled manually through entry boxes, sliders, etc., parameters of some of the filters and sources in ParaView can be changed interactively by manipulating 3D widgets in a 3D view. Often the 3D widgets are used to set the parameters approximately, and then the manual controls are used for fine-tuning these values. In the manual controls for each 3D widget, there is a check box for toggling whether the 3D widget is drawn in the scene. The label for the check box depends on the type of 3D widget being used. The following 3D widgets are supported in ParaView.
The line widget is used to set the orientation and the position of a line. It is used in both the stream tracer and elevation filters. The position of the line can be changed by clicking on any point on the line, except the endpoints, and dragging. To position the widget accurately, the user may need to change the camera position as well. Holding Shift while interacting will restrict the motion of the line widget to one of the X, Y, or Z planes. (The plane chosen is the one most closely aligned with the direction of the initial mouse movement.) To move one of the endpoints, simply use one of the point widgets on each end of the line. These are marked by spheres that become red when clicked. You can also reposition the endpoints by pressing the “P” key; the endpoint nearest to the mouse cursor will be placed at the position on the dataset surface beneath the mouse position. Left-clicking while the cursor is over the line and dragging will reposition the entire line. Doing the same with the right mouse button causes the line to resize. Upward mouse motion increases the length of the line; downward motion decreases it.
The show line check box toggles the visibility of the line in the 3D view.
The controls shown in Figure 8.2 can be used to precisely set the endpoint coordinates and resolution of the line. The X Axis, Y Axis, and Z Axis buttons cause the line to be along the selected axis and pass through the center of the bounds of the dataset.
Depending on the source or filter using this widget, the resolution spin box may not be displayed. The value of the resolution spin box determines the number of segments composing the line.
The plane widget is used for clipping and cutting. The plane can be moved parallel to its normal by left-clicking on any point on the plane except the line center and dragging. Right-clicking on the plane, except on the normal line center, and dragging scales the plane widget. Upward mouse motion increases the size of the plane; downward motion decreases it. The plane normal can be changed by manipulating one of the point widgets (displayed as cones that become red when clicked) at each end of the normal vector.
Shown in Figure 8.4, the standard user interface for this widget provides entry boxes for setting the center position (Origin) and the normal direction of the plane as well as toggling the plane widget’s visibility (using the show plane check box). Buttons are provided for positioning the plane at the center of the bounding box of the dataset (Center on Bounds) and for aligning the plane’s normal with the normal of the camera (Camera Normal), the X axis, the Y axis, or the Z axis (X Normal, Y Normal, and Z Normal, respectively). If the bounds of the dataset being operated on change, then you can use the Reset Bounds button to cause the bounding box for the plane widget to match the new bounds of the dataset and reposition the origin of the plane at the center of the new bounds. Using only the Center on Bounds button in this case would move the origin to the center of the new bounds, but the bounds of the widget would not be updated.
The box widget is used for clipping and transforming datasets. Each face of the box can be positioned by moving the handle (sphere) on that face. Moving the handle at the center of the box causes the whole box to be moved. This can also be achieved by holding Shift while interacting. The box can be rotated by clicking and dragging with the left mouse button on a face (not at the handle) of the box. Clicking and dragging inside the box with the right mouse button uniformly scales the box. Dragging upward increases the box’s size; downward motion decreases it.
Traditional user interface controls, shown in Figure 8.6, are also provided if more precise control over the parameters of the box is needed. These controls provide the user with entry boxes and thumb wheels or sliders to specify translation, scaling, and orientation in three dimensions.
The sphere widget is used in clipping and cutting. The sphere can be moved by left-clicking on any point on the sphere and dragging. The radius of the sphere is manipulated by right-clicking on any point on the sphere and dragging. Upward mouse motion increases the sphere’s radius; downward motion decreases it.
As shown in Figure 8.8, the center and radius can also be set manually from the entry boxes on the user interface. There is also a button to position the sphere at the center of the bounding box of the current dataset.
The point widget is used to set the position of a point or the center of a point cloud. It is used by the Stream Tracer, Probe Location and Probe Location over Time filters. The position of the point can be changed by left-clicking anywhere on it and dragging. Right-clicking and dragging anywhere on the widget changes the size of the point widget in the scene. To position the widget accurately, the user may need to change the camera position as well. Holding Shift while interacting will restrict the motion of the point to one of the X, Y or Z planes. The plane chosen is the one that is most closely aligned with the direction of the initial mouse movement.
As shown in Figure 8.10, entry boxes allow the user to specify the coordinates of the point, and a button is provided to position the point at the center of the bounds of the current dataset. If the point widget is being used to position a point cloud instead of a single point, entry boxes are also provided to specify the radius of the point cloud and the number of points the cloud contains.
The spline widget is used to define a path through 3D space. It is used by the Spline Source source and in the Camera animation dialog. The widget consists of a set of control points, shown as spheres in the 3D scene that can be clicked on with the mouse and dragged perpendicular to the viewing direction. The points are ordered and the path through them defines a smoothly varying path through 3D space.
As shown in Figure 8.12, the text control box for the spline widget allows you to add or delete control points and specify their locations exactly. You can hide or show the widget and can choose to close the spline to create a loop, which adds a path segment from the last control point back to the first.