7. Animation

In ParaView, you can create an animated scene where input data but also analysis and visualization parameters can change at each timestep.

When loading a time varying dataset, ParaView automatically loads the timesteps information. Then you can choose the current time, and the pipeline will be recomputed accordingly.

A property animation is created by recording a series of keyframes. At each keyframe, you set values for the properties of the readers, sources, and filters that make up the visualization pipeline, as well as the position and orientation of the camera. Once you have chosen the parameters, you can play through the animation.

Also, the results of the animation can be saved to different format from the File: menu.

• Save Animation: images files (one image per animation frame) or movies (depends on available codecs)

• Save Geometry: all geometries in scene with ParaView’s PVD file format

• Save Extracts: save datasets and screenshots as configured in the pipeline with Extractors sources.

• Export Animated Scene: for external viewer, as vtk.js format

image files or to a movie file. The geometry rendered at each frame can also be saved in file format, which can be loaded back into ParaView as a time varying dataset.

7.1. Time Manager

Time Manager is the main place where to control time. This is accessible from the View menu.

Fig. 7.1 Time Manager.

This panel is presented as a table. Above the table are controls that administer how time progresses in the animation.

Within the table, the tracks are organized into two sections. The first displays information about time varying data present in the pipeline. Each row match one temporal pipeline source, and its associated timesteps. The first row in the table, simply labeled Time, shows the scene times, i.e. the times that will be used when playing the scene. That can be a combination of pipeline source data times. The current displayed time is indicated both in the Time field at the top and with a thick, vertical line within the table.

Note that both the first and the last time labels of the timeline have special background. Click on them to enter Start Time and End Time entry-boxes and configure the start and end times for the animation. By default, when you load time varying datasets, the start and end times are automatically adjusted to cover the entire time range present in the data. The lock check-buttons just next to the Start Time and End Time labels will prevent this from happening, so that you can ensure that your animation covers a particular time domain of your choosing.

In the second part come the animation tracks. The Animations row contains widget to creates animations.

Fig. 7.2 Animation Tracks.

You choose a data source and then a particular property of the data source in the bottom row. To create an animation track with keyframes for that property, click the + on the right-hand side; this will create a new track. In the figure, tracks already exist for SphereSource1’s Phi Resolution property and for the camera’s position. To delete a track, press the X button. You can temporarily disable a track by unchecking the check box on the left of the track. To enter values for the property, double-click within the white area to the right of the track name. This will bring up the Animation Keyframes dialog. Double-clicking in the camera entry brings up a dialog like the one in Fig. 7.3.

Fig. 7.3 Editing the camera track.

From the Animation Keyframes dialog, you can press New to create new keyframes. You can also press Delete or Delete All to delete some or all of the keyframes. Clicking New will add a new row to the table. In any row, you can click within the Time column to choose a particular time for the keyframe, and you can click in the right-hand column to enter values for the parameter. The exact user interface components that let you set values for the property at the keyframe time vary. When available, you can change the interpolation between two keyframes by double-clicking on the central interpolation column.

Within the tracks of the Time Manager , the place in time where each keyframe occurs is shown as a vertical line. The values chosen for the property at that time and the interpolation function used between that value and the next are shown as text, when appropriate. In the previous figure, for example, the sphere resolution begins at 10 and then changes to 20, varying by linear interpolation between them. The camera values are too lengthy to show as text so they are not displayed in the track, but we can easily see that there are four keyframes spaced throughout the animation. The vertical lines in the tracks themselves may be dragged, so you can easily adjust the time at which each keyframe occurs.

Did you know?

You can quickly add a simple animation track and edit the keyframe without using the Time Manager by using Animation Shortcut . First, enable Show Animation Shortcut from Settings dialog (on the General tab, search for the option by name or switch to advanced view). Then, several of the animatable properties on the Properties panel will have a icon. Click this icon to add a new animation track for this property and edit it.

7.2. Scene time configuration

7.2.1. Time controls

The Time Manager has a header bar that lets you control some properties of the animation itself, as you can see in Fig. 7.4.

Fig. 7.4 Time Manager Widgets.

The Time entry-box shows the current animation time, which is the same as shown by a vertical marker in this view. You can change the current animation time by either entering a value in this box, if available, or by dragging the vertical marker. The second entry-box is the timestep index. You can also edit it.

If the scene does not use any pipeline sources to get its list of times (see below), you can also edit Number of frames to set the total number of frames for the scene.

The Stride parameter, available in advanced mode, allows to jump by this number of timesteps when navigating through times.

7.2.2. Time list

ParaView supports two modes to configure scene times. The time list can either come from the data themself or it can be generated. We call them Snap to Timestep and Sequence respectively.

Fig. 7.5 Time Manager Sequence.

In Sequence mode, the number of frames is controlled by the No. Frames spinbox. Times are evenly spaced between Start and End time. This is the preferred mode when working with non-temporal data. This is activated when none of the Time tracks are enabled, i.e. the checkbox left to the Time label of first track is disabled.

In the figure, the main timeline has 12 ticks. They do not match the times from the data, as expected for a sequence.

Fig. 7.6 Time Manager Snap to timesteps.

In Snap To TimeSteps mode, the number of frames in the animation is determined by the number of time values in the dataset being animated and thus cannot be changed. This is the animation mode used by default by ParaView when a dataset with time values is loaded. Then playing the animation means playing through the time values of the dataset one after the other. This is enabled when at least one Time track is checked.

In the figure, only can.ex2 is checked so the scene knows only about its timesteps: the main timeline has same ticks as the can.ex2 track.

Did you know?

You can change the precision (number of significant digits) displayed by the animation clock by changing the Animation Time Precision value in the Settings under the General tab.

7.3. Animating time-varying data

We saw that the main scene of ParaView can know about the times available from a pipeline source, such as a reader that produces time varying data. Then a current time is set at the scene level, and by default the pipeline is updated to the relevant time.

But what happen when asking for a time that does not exist in the data? How to do some properties animation at a fixed data time? Can I animate the time itself?

ParaView offers one answer to all those questions: the Time Keeper. This is an animation track, visible only in advanced mode. The Time Keeper maps the scene time to a new time used to update the pipeline. The default mapping simply maps the scene time to itself.

But you can uncouple the data time from the animation time so that you can create complex animations.

If you double-click in the TimeKeeper – Time track, the Animation Keyframes dialog, an example of which is shown in Fig. 7.7, appears. In this dialog, you can make data time progress in three fundamentally different ways. If the Animation Time radio-button is selected, the data time will be tied to and scaled with the animation time so that, as the animation progresses, you will see the data evolve naturally. If you want to ignore the time varying nature of the data, you can select Constant Time instead. In this case, you choose a particular time value at which the data will be displayed for the duration of the animation. Finally, you can select the Variable Time radio-button to have full control over data time and to control it as you do any other animatable property in the visualization pipeline. In the example shown in Fig. 7.7, time is made to progress forward for the first 15 frames of the animation, backward for the next 30, and forward for the final 15.

Fig. 7.7 Controlling Data Time with keyframes.

7.4. Animating the camera

Just like you can change parameters on sources and filters in an animation, you can also change the camera parameters. You can add animation tracks to animate the camera for all the 3D render views in the setup separately. To add a camera animation track for a view, with the view selected, choose Camera from the first drop-down menu. The second drop-down list allows you to choose how to animate the camera. Then click on the + button. There are three possible options, each of which provides different mechanisms to specify the keyframes. It’s not possible to change the mode after the animation track has been added, but you can simply delete the track and create a new one.

7.4.1. Follow data

In this mode, the camera focal point and position is changed to keep the data centered in the view. It does not change the camera zoom level, however.

7.4.2. Interpolate cameras

In this mode, you specify camera position, focal point, view angle, and up direction at each keyframe. The animation player interpolates between these specified locations. As with other parameters, to edit the keyframes, double-click on the track. It is also possible to capture the current location as a keyframe by using the Use Current button.

Fig. 7.8 Setting camera animation parameters.

It can be quite challenging to add enough keyframes correctly to ensure that the animation results in a smooth visualization using this mode. However, it is the preferred mode if you want fine control on a few cameras.

7.4.3. Follow path

In this mode, you get the opportunity to specify the path taken by the camera position and the camera focal point. By default, the path is set up to orbit around the selected objects. You can then edit the keyframe to change the paths. This is the preferred mode if you want to control the global motion more than exact points of view.

Fig. 7.9 shows the dialog for editing these paths for a keyframe. When Camera Position or Camera Focus is selected, a widget is shown in the 3D view that can be used to set the path. Use CTRL + Left Click to insert new control points, and ⇧ + Left Click to remove control points. You can also toggle when the path should be closed or not.

Fig. 7.9 Creating a camera path.

This mode makes it possible to quickly create a camera animation in which the camera revolves around objects of interest. Clicking on the Orbit button will pop up a dialog where you can edit the orbit parameters such as the center of revolution, the normal for the plane of revolution, and the origin (i.e., a point on the plane where the revolution begins). By default, the Center is the center of the bounds of the selected objects, the Normal is the current up direction used by the camera, while the origin is the current camera position.

Fig. 7.10 Creating a camera orbit.

7.5. Playing an animation

Once you have designed your animation, you can play through it with the VCR controls toolbar seen in Fig. 2.8.

Fig. 7.11 VCR Controls and Current Time Controls toolbars in paraview.

Note that the frames are rendered as fast as possible. Thus, the viewing frame rate depends on the time needed to generate and render each frame.

When you play the animation, you can cache the geometric output of the visualization pipeline in memory. When you replay the animation, playback will be much faster because very little computation must be done to generate the images.

7.6. Explore an animation using Python

The following Python commands allow you to get and explore an animation scene.

Just like you can navigate through timesteps in paraview’s user interface, you can use Python commands to do the same. These commands are available through an animation scene object, retrieved with:

>>> scene = GetAnimationScene()

This object has several methods available to change which animation timestep is shown:

>>> scene.GoToFirst()
>>> scene.GoToLast()
>>> scene.GoToNext()
>>> scene.GoToPrevious()

Additional methods are available to start and stop playback of the animation:

>>> scene.Play()
>>> scene.Stop()
>>> scene.Reverse()

Play() plays the animation from current timestep to the last. Reverse() plays the animation in reverse from the current timestep to the first.

Finally, you can access the available times in all loaded datasets using

>>> times = scene.TimeKeeper.TimestepValues
>>> times
[0.0, 0.1, 0.2]

Some useful scene properties are:

>>> scene.NumberOfFrames = 100
>>> scene.PlayMode = 'Snap To Timesteps' # or 'Sequence'

You can also create your own animation based on properties of a source/filter

# create a new 'Sphere'
sphere1 = Sphere(registrationName='Sphere1')

# get active view
renderView1 = GetActiveViewOrCreate('RenderView')

# show data in view
sphere1Display = Show(sphere1, renderView1, 'GeometryRepresentation')

# trace defaults for the display properties.
sphere1Display.Representation = 'Surface'

# reset view to fit data
renderView1.ResetCamera(False, 0.9)

# update the view to ensure updated data information
renderView1.Update()

# get animation track
sphere1StartThetaTrack = GetAnimationTrack('StartTheta', index=0, proxy=sphere1)

# create a new key frame
keyFrame0 = CompositeKeyFrame()

# create a new key frame
keyFrame1 = CompositeKeyFrame()
keyFrame1.KeyTime = 1.0
keyFrame1.KeyValues = [360.0]

# initialize the animation track
sphere1StartThetaTrack.KeyFrames = [keyFrame0, keyFrame1]

# get animation scene
animationScene1 = GetAnimationScene()

animationScene1.Play()