Animation

Animation Overview: All VAPOR data sets (VDC's) are indexed by time.  The time step, a non-negative integer, is the same for all renderers in a visualizer.  Each VAPOR renderer operates on the data for the current time step.  The animation tab controls the changing of the current timestep.  There is also support in the animation tab for key-framing.  By using key-framing, users can specify the position and motion of the camera, and the changing of the current timestep, during an animation sequence.

Animation settings can apply to one or many different visualizers, depending on the Local/Global setting.

Time step control:  The current time step can be controlled either by the animation toolbar or by the animation tab.   In the animation tab, there is both a "Current Frame" and a "Timestep" setting.  These two (current frame and timestep) are equal when key-framing is disabled.  When key-framing is enabled, the "Current Frame" goes forwards and backwards during the animation, however the change of Timestep is controlled by the key frame settings, and may move differently from the Current Frame.  Likewise, the Start and End textboxes indicate the first and last time step to be played when key framing is disabled.  When key framing is enabled, the Start and End textboxes go from 0 to the last frame in the key-framed animation sequence.

The animation toolbar (at the top of the main VAPOR GUI window) has buttons to play forward or backwards or stop; to move one step forward or backward, and a text box indicating the current time step, as shown:

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The animation tab has additional buttons for jumping to the start or end of the animation, plus the ability to enable continuous replay, to set the start and end time step, and to jump multiple steps at a time.

Global/Local scope:  The Global/Local scope selector at the top of the animation tab is only used when there are multiple visualizers.  With Global scope, all visualizers use the same time step.  With Local scope, a visualizer has its own time step (and animation control) independent of the other visualizers.  This can be used to make side-by-side comparison of the visualized data at different time steps.

Animation speed: The speed is of course limited by the time for the various renderers to complete, however the animation panel can influence the frame rate.   The "Max Frames/Second" value determines the maximum frame rate, and will force the rendering to perform no faster than specified.

Key Frame Settings:  The key frame settings enable users to specify a moving camera position, and to control how the time steps in the data change as time progresses.  Refer to the page "Creating a key-framed animation" for more detailed instructions.  The key frame settings include the following:

• Enable Keyframing:  When keyframing is disabled, the current frame is always the same as the current timestep.  When disabled, the current timestep changes according to the key frame settings. 
• Key Index is an integer between 0 and the final key frame. This indicates the key frame that is being set in this panel.
• Time step indicates the time step in the data that will be displayed at the key frame associated with Key Index.
• Speed indicates the camera speed, as measured in scene diameters per frame, at the key frame associated with the current Key Index.
• Frame index indicates the frame number (of the full keyframed animation sequence) associated with the current Key Index.
• The "Advance with Time steps" checkbox is used to specify that that data time steps will advance at a fixed rate, synchronized with the frame number, between the previous key frame and the current key frame.  By default (starting with VAPOR 2.5), this checkbox is checked whenever the time step changes between the previous and current key frame.
• Timesteps per frame indicates the time step rate of change between the current key frame and the previous key frame.  It can only be set when "Advance with time steps" is checked.
• No. of frames indicates the number of frames between the previous key frame and the current key frame.  This value can only be specified if the camera speed is zero.
• When you click the "Insert new key frame" button, a new key frame is created immediately after the current Key Frame (as indicated by the Key Index).  This new key frame will use the current viewpoint and current timestep, and will use the default camera speed (which is either 0.1 or the speed of the previous keyframe.)
• When you click "Set Current Key", the current keyframe (as indicated by the key index) is modified to have its viewpoint become the current viewpoint, and its time step becomes the current time step.
• The Delete button deletes the current key frame.
• When the "Go to Key" button is clicked, the current viewpoint is set to the viewpoint associated with the current key frame, and the current time step is set to the time step in the current key frame.

Explicit Time Steps:  Sometimes the valid time steps in a data set are not simply a collection of evenly spaced integers.  When you animate through such data, VAPOR will automatically skip over time steps for which there is no data.  To better control such a sequence of time steps, check the box labelled "Use Explicit Time Steps".  When checked, the time-stepping is limited to the time steps that are specified in the list of time steps.  The time steps are necessarily increasing but any time steps may be skipped.

Capturing animation:  To capture a sequence of images: From the Capture menu, choose "Begin image capture sequence in visualizer No. ...", and choose a jpeg or tiff file name, such as "file.tif".  Then perform the animation, either by clicking on the "play" button, or rotating the scene, or making other changes in the visualization.  Every time the visualization changes, another image will be captured.  The names of the captured files are constructed from the name you supplied by adjoining a 4-digit number to the file name; e.g. file0000.tif, file0001.tif, file0002.tif, etc.  When the animation is complete, click on the Capture menu again, and select "End image capture sequence".  If you need to convert the sequence of jpeg or tiff images to a movie file, this can be done with various software tools such as QuickTime Pro or ffmpeg.

Displaying the time:  The current time step index can be displayed in the scene.  This is enabled under "Time Annotation" in the Visualizer Features Panel.  If the data has time stamps (e.g. WRF or Ocean data) then the current time stamp can be displayed in the scene.  The text size, position, and color for this annotation can also be set in the Visualizer Features Panel.