Creating a key-framed animation

Keyframing in Vapor 2

VAPOR users can specify animation sequences using key framing.  To design a key-framed animation sequence, the user specifies the camera position (i.e. viewpoint) and the time step at a few different animation frames.  VAPOR will smoothly interpolate the time step and the viewpoint so that the camera smoothly moves from one key-frame to the next key-frame, and the time step is linearly interpolated between its values at the key frames. 

The following process can be used to create a key framed sequence.  Begin with the "Enable Key Framing" checkbox un-checked.  The "Current Key Index" should be 0.

1. First, navigate to the viewpoint where you want the animation to start.  Also set the current time step to the time step in the data where the animation will start.
2. Click the button "Set current key".  This will make the first key frame use the current timestep and viewpoint.
3. Then, navigate to the next viewpoint and set the current timestep to be the time step that you want displayed at the second viewpoint.  The next viewpoint should not be very far from the first viewpoint or you may find that the interpolation moves the camera in unexpected ways.
4. Click the "Insert new key frame" button.
5. Repeat steps 3. and 4. until you have specified all the desired key frames.

Check the "Enable Key Framing" checkbox to see the resulting animation.  Set the Current Frame to 0 and click the play button to see how the animation proceeds over time.  You may find it useful to adjust the keyframes as follows:

• If the camera is moving too fast or too slow at a keyframe, you can adjust the speed.  Set the Key index to the key frame to be adjusted, and change the value of "Speed" to be larger or smaller.  The time step at the key frame can also be changed.
• Note that if the checkbox "Advance with Time steps" is checked, then the speed cannot be edited because the speed is automatically calculated so as to synchronize the frame counter with the time steps. This can be un-checked and the speed can be manually set, if you do not want the frames to be synchronized with the time steps.
• Set the speed to be zero if you want the viewpoint to be stationary at a key frame.  If you would like the viewpoint to remain stationary while the time step is advanced, then do the following:

1. Set the current key index at the key frame where you want the camera to stop
2. Set the speed to be zero (at that stopped key index)
3. Without changing the viewpoint, click "Insert New Key frame". This will result in a new key frame with speed 0 at the same viewpoint as the frame where you stopped.
4. To control the number of frames between the first stopped key frame and the second stopped key frame:

• Set the key index at the second stopped key frame.
• Set the desired time step at the second stopped key frame.
• Check the box "Advance with time steps"
• Set the "Timesteps per frame" to be the rate (in timesteps per frame) at which you want the time steps to advance while the camera is stopped. Note that this value must be an integer.

• Note that you cannot specify two adjacent keyframes to have different viewpoints if their speeds are zero.  If you attempt to set two adjacent key frames to have speed zero and the camera positions are different, then VAPOR will insert a hidden key frame in between the two stationary frames, but (starting with VAPOR 2.5) this hidden key-frame will not appear in the key frames displayed.

It is often useful to have the time steps advance at a constant rate (say 1 time step per frame) while the camera is moving.  This can be obtained as follows:

1. Specify the first and second camera positions and the associated time steps, as described above, i.e., set the viewpoint and the time step at each of the two key frames, and click the "Set current key" button to establish the two viewpoints and time steps.
2. The "Advance with time steps" checkbox will be checked (if the two timesteps are different).
3. Set the "Timesteps per frame" to the desired timestep advance rate, an integer; by default it is 1.

Tips: 

For best control of camera motion, have frequent key frames.  Between each pair of key frames have simple camera motion, such as a zoom or a translate or a rotate.  Combining rotations, translations and zooms in one move can result in unexpected camera behavior.

When zooming into a scene, do not specify viewpoints that pass through the rotation center (which is a point in the center of the camera view).  The key-frame interpolation cannot interpolate through the rotation center.  To specify an animation path that passes through the center of the scene, specify the rotation center as a point on the opposite side of the scene, and use that rotation center during the zoom-in.  Check "viewpoint and lighting" for instructions on specifying the rotation center using the probe.