GMS:Animations

One of the most powerful visualization tools in GMS is animation. Animations can be created with transient or steady state data. The view angle and zoom factor can be changed during the animation as well. Animations are saved in the Windows (*.avi) format. AVI files can be played back externally to GMS using a variety of applications and can be inserted into multi-media documents and applications.

A new animation can be created by selecting the Animate command from the Display menu.

Animation Options

There are 5 options available when creating an animation:

Option	Type
Data Set	Transient
Particle Tracking	Transient
Cross-sections / Iso-surfaces	Steady State
Flow Trace	Steady State
Moving View	N/A

Transient vs. Steady State Animation

All of the options except Moving view are either considered Transient or Steady state. You cannot use a Transient option and a Steady state option at the same time. Moving view, however, can be used by itself or in conjunction with any combination of the other options.

The typical case for choosing to do a transient animation is when you have a transient solution generated by a model. The transient animation could illustrate how vectors, contours, fringes or iso-surfaces change at different solution times. A transient animation can also be used to show particle tracking over time, even with a steady state solution.

Steady state animation can only be performed using 3D grids or 3D meshes. A steady state animation can be used with a steady state data set, or with one time step of a transient data set. Two options are available for steady state animation: Cross-section / Iso-surface animation and Flow trace animation.

Data Set Animation

Transient data set animation can be used with any object with a transient data set. As each frame is generated, a set of values corresponding to the current time is loaded into memory and the image is redrawn using the current display options. Thus, if the contour display option is selected, the contours will vary from frame to frame according to the changes in the data set.

The total number of frames generated in the animation can be defined by either matching the time steps (one frame per time step) or by using a constant interval (e.g., one frame for every two hour interval). If the Match time steps option is chosen, extra frames can be created between each time step if necessary using linear interpolation of the data values at the specified time steps.

Particle Tracking Animation Particle tracking can be animated to show how pathlines grow over time. Although it is considered a Transient option in the table above, this option can be used with a transient or a steady state solution. Only the forward tracking particle sets can be animated.

If Particle tracking is selected by itself, you can choose how many frames you want in the animation. GMS will then compute the time at which to generate each frame by dividing the total animation time evenly by the number of frames. The animation begins at the minimum start time of all forward tracking particle sets, and ends at the maximum travel time of all particles (in all forward tracking particle sets).

Cross-section / Iso-surface Animation

If the Geometric surface animation option is chosen, a cutting plane and/or an iso-surface can be animated. If the Animate cutting plane over specified XYZ range option is chosen, an x, y, and/or z cutting plane is incrementally moved through the mesh or grid from the specified beginning location to the ending location as each frame is generated. This generates an animation showing a moving cross section. If the Animate iso-surface option is chosen, a single iso-value is incrementally varied between the specified beginning and ending values and a different iso-surface is generated for each frame based on the value.

Flow Trace Animation

This option is not supported in GMS version 5 and greater.

If the Animate flow trace option is chosen, a flow trace animation of the steady state vector data on 3D grid or 3D mesh cross sections is generated. Flow trace animation is a special type of animation that is similar to particle tracking. A series of particles is randomly generated on the cross sections and it is traced through time. Each particle has a limited life span. As a result, the particles appear as a series of streaks. Flow trace animation can result in highly intuitive images of a vector field.

If there is no vector data set or cross section associated with the current 3D grid or 3D mesh, the Animate flow trace option and Flow trace options button are dimmed. The Animate flow trace option is also dimmed if the Flow trace option is not selected in the Cross Section Options dialog. If the active vector data set is transient, only the current time step is used to generate the flow trace animation.

The Avg. number of particles per triangle edit field specifies the density of particles to be generated in the animation. The Decay ratio specifies the amount of time necessary for a particle path to decay as it passes points in the cross section. The Velocity magnitude limit and Velocity direction limit specify the distance that a particle will travel between consecutive frames.

Moving View

The Moving view option can be used by itself or in conjunction with any combination of the other options. This option can be used to change how you view the data as the animation proceeds. You can define views and associate them with particular frames of the animation. When the animation is generated, GMS will interpolate between the defined views to determine what the view should be at every frame.

CODEC

Starting in GMS 6.5 you can choose what codec you use to create your AVI movie. GMS will search your computer for all compatible codecs and they will be available in the pull down menu.

Animation Playback

Once a new animation has been generated, GMS launches the AVI player and plays the animation. The speed of playback can be adjusted using the Speed scroll bar. The maximum speed depends on the speed of the computer and the size of the image being animated. The smaller the image, the faster the maximum playback speed.