GMS:Animations

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Example of the Animation Wizard – Options dialog.

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.

The animation tools are included with all editions of GMS, including the community version.

Animation Options

There are multiple options available when creating an animation:

Option Type
Dataset Transient
Particle Tracking Transient
Cross-sections / Isosurfaces 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. GMS does not allow use of 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 a projects has a transient solution generated by a model. The transient animation could illustrate how vectors, contours, fringes or isosurfaces 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 dataset, or with one time step of a transient dataset. Two options are available for steady state animation: Cross-section / isosurface animation and flow trace animation.

Dataset Animation

Transient dataset animation can be used with any object with a transient dataset. 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 dataset.

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, choose how many frames are wanted 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 / Isosurface Animation

If the Geometric surface animation option is chosen, a cutting plane and/or an isosurface 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 isosurface option is chosen, a single isovalue is incrementally varied between the specified beginning and ending values and a different isosurface is generated for each frame based on the value.

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 to view the data as the animation proceeds. 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.

Flow Trace Animation

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 dataset 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 dataset 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.

CODEC

Starting in GMS 6.5 choose which codec to use to create an AVI movie. GMS will search the 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.