«Animation's Role in Visualization Animation brings life to otherwise inanimate objects and greatly enhances one's understanding of geometry, motion ...»
Animation for Science and Engineering
Kent Misegades, President, CEI Inc.
Animation's Role in Visualization
Animation brings life to
otherwise inanimate objects
and greatly enhances one's
geometry, motion and
Pioneered by cartoonists
such as Walt Disney in
the early part of the 20th
century, animation is a
mature artistic technique
that in recent years has
greatly benefited from
While the use of computers to create animations for entertainment media has become commonplace through the advent of highly sophisticated software packages, its use in scientific visualization is far less widespread. CEI has long recognized the benefits of computer animation for scientists and engineers and has provided a powerful set of capabilities for the creation and display of animations in its products. The following article describes these features and how they have been implemented in our products, which are briefly
! EnSight -- general-purpose visualization software for science and engineering ! EnSight Gold -- high-end visualization package for very large data sets and virtual reality ! EnLiten -- 3D model and animation viewer ! EnVideo -- animation player ! EnVe -- animation editor EnSight and EnSight Gold are used to visualize data and create animations. These can be played in EnSight or recorded to a number of different formats. EnLiten is used to view models as they were rendered and animated in EnSight. EnVideo is a simple animation player. EnVe is used to edit multiple animation sequences into one long movie. (In the following paragraphs, references to EnSight apply also to EnSight Gold, whose capabilities constitute a superset of those in EnSight.) The following paragraphs are meant to provide you with an introductory description of the means to create, edit, play and record animations in our products. This is not an exhaustive user guide on animation, and it is recommended that you refer to the extensive descriptions of these capabilities found in the online manuals for each product.
Types of Animations and their Creation in EnSight
The following different types of animations can be created in EnSight:
! Streamline Animation ! Plane Sweep Animation ! Isosurface Animation ! Flipbook Animation ! Create Data Animation ! Transient Data Animation ! Linear Load Animation ! Mode Shape Animation ! Keyframe Animation Each of these will be described in detail in the following sections.
Additional information can also be found in the help documentation for each product.
Streamline Animation Any particle trace that has been created in EnSight, i.e. steady streamlines, pathlines from transient flows, massless or massed particles, or traces computed or measured externally and imported into EnSight, can be animated using the options found in the quick interaction area for the streamline feature. Select the particle trace part(s) that are to be animated from the part list and select Animate from the quick interaction options. A single pulse will move in the positive time sense from the start to the end of each trace. As the default color of this pulse is identical to the color of the trace, you may find it useful to deactivate the visibility of the trace itself, clicking the visibility icon (eye) found on the left of the EnSight GUI.
There are many options to affect the appearance of the trace animation.
These are found in the animation option dialog, labeled Animate... in the quick interaction area. Pulse length, speed, color, thickness, max time, and frequency can be modified. A sphere can be displayed on the head of the pulse, the size of which can be constant or scaled according to a local variable; the head would grow, for example, in areas of high temperature or velocity magnitude. If a transient solution is animated using pathlines, it is possible to synchronize the trace animations to a different type of animation, such as a flipbook animation (see below) of moving geometry or a changing variable displayed somewhere in the solution.
The animation options are intuitive and the result of changes will be seen immediately. The best means to understand these options is to experiment with a small number of traces, making adjustments to each option and observing the effects of these changes. Note that while it is possible to animate traces on a per part basis, animation settings are global, i.e. they apply to all traces animated.
Plane Sweep Animation EnSight provides several ways to animate the motion, or sweep, of a plane through model parts. The plane might actually be one of the
several types of clip planes that can be created in EnSight's Clip feature:
IJK, XYZ, Line, or Plane. (Cylinder, Sphere, Cone, XYZ Box, Revolution Tool and Revolve 1D Part types of Clips cannot currently be animated in EnSight). One might be interested in observing how a variable used to color this plane changes as it sweeps across the model. Another part could be attached to this clip, such as contours of a variable or vector arrows, and one could observe these sweeping across the model.
For IJK and XYZ clips, one can quickly sweep in the direction of the coordinate (I/J/K or X/Y/Z) used to create the initial clip by selecting Interactive Auto or Interactive Auto Cycle for any such clip parts from the options in the Quick Interaction area for clips. The parameters Range Min and Max that appear when using Interactive Auto or Interactive Auto Cycle limit the extent of the sweeps. The parameter Auto Delta defines the granularity of the sweep; decreasing this value results in finer and thus slower sweeps over a range defined by Min/Max.
A second, more general type of plane sweep is available in the create data type of flipbook animation, described below.
Isosurface Animation Similar to plane sweeps described above, isosurfaces can be animated over a range of Min/Max values. The same options to adjust the Min, Max and Delta values, found in the Quick Interaction area for isosurfaces, apply to animated isosurfaces as for animated planes.
A second, more general type of isosurface animation is available in the create data type of flipbook animation, described below. Note that if a component of the coordinate vector variable is used as the basis of an isosurface, a constant XYZ clip results, which itself can be animated as an isosurface, equivalent to an XYZ clip plane sweep Flipbook Animation The term flipbook originated in the simple printed animations popular in the early part of the 20th century. One flipped through the pages rapidly to view one or more animated cartoons. EnSight mimics this, loading a series of images into its flipbook memory to be played back rapidly.
Flipbooks can be either an object type, where the entire geometry is loaded for each page of the flipbook, or an image type, where only an image pixel representation of the model is loaded. Object flipbooks require more memory, but permit one to modify the orientation and visibility of model parts during the animation. Image flipbooks require less memory, but the model orientation and appearance cannot be altered without reloading the flipbook.
Four different types of flipbooks can be loaded and animated:
! Create Data Animation -- create a series of clip planes or isosurfaces ! Transient Animation -- loads a series of time steps or time slices from a transient model ! Linear Load Animation -- animate model deformation by scaling a displacement vector ! Mode Shape Animation - animate the cyclical motion of a model's mode shape For each of these types of flipbooks described below, a number of options are provided in EnSight to play the loaded pages automatically or manually, stepping through the pages in either direction. One can also modify the speed, direction or extent of the animation by adjusting the parameters found in the Modify Run parameters. Changes to the model part representation, other than part visibility and transparency, do not result automatically in changes to the flipbook. These require a new flipbook to be reloaded.
For complex scenes and/or large models, a flipbook, especially one of the object type, can result in a substantial allocation of memory. Therefore it is advisable to delete a flipbook if it is no longer needed. Lower memory usage will result if all model parts that are not to be visible in the flipbook animation are either deleted or their element visual representation is set to NonVisual prior to loading the flipbook.
Create Data Animation A create data flipbook does just that: For each page, a new clip plane or isosurface is created. For clip planes, one first must create a clip plane using the IJK, XYZ, Line or Plane options. The resulting clip is made interactive and positioned at the starting location of the desired motion in the flipbook. Switching now to the flipbook Quick Interaction parameters, a Create Data load type is selected, Start is selected, and the Number of Flipbook Pages to Create is set to the desired number of pages, or total number of clips to create between the start and stop positions. The plane is now moved to its final position by adjusting the appropriate parameters or tools, depending on how the plane was originally created. Stop is then selected for the flipbook, and the two limits have now been set. Selecting Load generates the intermediate positions of the clip plane/line. Note that for planes defined using the plane or line tool, the transformation, or motion of the clip, is interpolated linearly between the Start and Stop positions. With the flipbook loaded, the animation can now be played per the instructions in the previous paragraphs dealing with flipbook animations in general.
A similar approach is followed if an isosurface animation is to be loaded in the flipbook. Create the first isosurface and set the interactivity to Manual, select Start and Number of Flipbook Pages to Create in the flipbook parameters as before, adjust the isosurface to the final value, then select Stop and Load in the flipbook parameters.
One might wonder why clips and isosurfaces can be animated through both their respective Quick Interaction parameters as well as by a Create Data flipbook animation. While isosurfaces and clips can indeed be quickly animated using the Min/Max/Delta parameters as described above, the flipbook also provides a means to animate clipped lines defined using the line tool and clip planes defined using the plane tool, allowing more arbitrary motion during plane sweeps. The flipbook animator also permits image flipbook animations (resulting in lower memory requirements) and a means to record animations, not available in the clip and isosurface animators.
Transient Data Animation The most common type of flipbook is a Load Type Transient animation.
One simply creates a desired visual (background, part visibility, coloring, newly created parts, annotation, plots -- the sum of all graphical entities as they appear in the graphics window) and loads the flipbook. Control is provided for the range of time steps or solution time (Adjust Beg/End Time...) as well as for the step increment or time slice (Increment Time by) to be taken when loading the flipbook. If particle paths (time accurate) have already been computed, these can also be animated and are by default synchronized to the loaded flipbook when it is played.
Static structural analyses result typically in a displacement vector and one or more scalar, vector or tensor variables representing the state of the model upon application of a given load. The nature of a static analysis permits one to scale the load and the resulting displacement linearly from unloaded to the fully loaded state. A linear load animation depicts the transition from these two states. Before loading a linear load flipbook, apply the displacement vector variable to the appropriate model parts, and color these by an appropriate variable if desired. The flipbook will scale the displacement vector from zero to the value of the vector, and vary the color from its lowest level to the color palette chosen for the variable by which the parts are colored.
Linear load animation of ANSYS cantilever beam Mode Shape Animation Structural analysis software can be used to predict the vibrational modes for an excited structure, also referred to as an Eigenvalue or mode shape solution. Such computations result in a displacement vector for each vibrational mode, or input load frequency. By animating the motion of a model from the positive to the negative extremes of this displacement, it is possible to gain an understanding of the relative importance of each vibrational mode. Before loading a mode shape flipbook, apply the displacement vector variable to the appropriate model parts. The flipbook will automatically scale the displacement vector from its negative to its positive extreme.
Keyframe Animation Keyframe animations depict model details and results. By saving a series of key frames, or model positions, then interpolating between these positions, it is possible to create smooth fly-arounds, fly-throughs or even part explosions for a given model. One begins by choosing the initial desired position of the model and saving this position, or keyframe, by selecting the save button in the Quick Interaction area for keyframe animations. The model is then moved to the next desired position, a new keyframe is saved, and so forth. When the keyframe is run, the model will move smoothly from one keyframe to the next.
Selecting the option Animate Transparency Change will include changes in part transparency between keyframes, allowing parts to fade in or out during playback of the animation. Selecting the option Use Interactive Iso/Clip will record the value of an interactive isosurface or the position of an interactive clip (IJK, XYZ, Plane, Line type of clips) along with the model part position at each keyframe. Saving a series of different clip positions at each keyframe allows complex motions of plane sweeps, such as along the axis of a manifold or any other curved model part.