# The Parametric Animation Panel

### The Pisces Parametric Animation Panel.

The parametric animation panel can animate a two-parameter family
of model along a one-parameter path in parameter space. In other
words, if a model depends on the parameters *(a,b)*, then the
parametric animation panel allows the user to animate level sets of
the model along any path *(a(t), b(t))*.
## How it works

The animation is created by the following
algorithm:
- The step size is computed by taking the difference
between
**Ending t** and **Starting t** and dividing the
difference by the **Steps**.
- The current values values of the parameters to animate are saved.
We will denote these parameters as
*(a,b)*.
- The value of
**Current t** is set to the value of
**Starting t**. This value and the Tcl expressions
next to the parameters to animate are used to determine the point
*(a(t0), b(t0))* which will be used as the
parameter values for the initial level set.
- The
**Algorithm** is called to compute the level set.
- The value of
**Current t** is incremented by step size.
- If the value of
**Current t** is less then or equal to
the **Ending t** then go to the previous step.
- The value of the animation parameters are restored.

## Controlling the Algorithm from Pisces

The parametric animation panel has the following fields:
**Steps**
- The number of frames of animation that will
be produced. This must be a positive integer.
** Starting t**
- The value that the independent variable
takes for the first frame of the animation.
** Ending t **
- The value the independent variable takes for the
last frame of the animation.
**Current t **
- The current value of the independent variable.
**Variable/Expression**
- The menus and Tcl expression in these fields determine the
parameters to animate and determine the parametric
paths that the parameters will follow. The main
point to remember about Tcl expressions is that you must
place a $ (dollar sign) in front of the name of the variable
(which is always
*t*).
** Algorithm **
- This menu selection determines method of
computing the level set. The parameters for each
algorithm may be set using
the control panel specific to each algorithm.

To see the animation press the **Go** button. To step through
the animation one frame at a time, you may press the **Step**
button.
The animation path you have specified may be viewed by pressing the
**Show Parametric Path** button.

### Known Bugs

Same as for the animate panel. Also, the name of
the independent variable *must* be *t*.
### Bug Reports

software@geom.umn.edu
### Implemented By

John Golden and
Erik Streed.

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Last modified: Sun Nov 26 18:50:32 1995

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The Geometry Center,
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