ANIMATION

Contents

# Toons

To create an animation, just do the following:

- Run the numerical simulation for however long you need it or run it once the toon is loaded.

- Using a text editor create a description of the animation using the little scripting language described below .

- Click on the `(V)iew axes` `(T)oon` menu item from the main XPP window to bring up the animation window.

- Click on the `File` item in the animation window that pops up and give it the name of your script file.

- If the file is OK, click on `Go` item and the animation will begin.

- Click on the little box in the upper right for animation on the fly -- the animation runs along with the simulation!

## The animation window

A resizeable window will pop up when you choose the `Toon` item form the `Viewaxes` submenu. This has 10 buttons on it. They are

- File Click on this to load a new animation file. Hereafter, I will call these ani files. The usual extension will be filename.ani.

- Go Click on here after you have loaded an ani file and it will run.

- Reset This moves the animation back to the beginning

- Fast speeds up the animation

- Slow slows it down

- Pause pauses the animation. Go restarts it from where it started. This is very sluggish and it takes a long time to respond to it. I hope to fix this someday.

- Skip sets the numbers of frames to skip

- »»»» Move forward one frame

- «««« Move back one frame

- Mpeg Store a series of ppm files for use with the mpeg_encode program. This takes a ton of disk space. Better yet, use the anigif option which creates an animated gif file. 600 frames can be as little as 500K so it wont eat up disk space.

Some computer systems cannot produce the required amount of graphics memory for a pixmap and if this happens, you cannot currently run the animation. You will be told this and the animation window will never appear.

## DASL: Dynamical Animation Scripting Language

In order to use the animation components of XPP, you must first describe the animation that you want to do. This is done by creating a script with a text editor that describes the animation. You describe the coordinates and colors of a number of simple geometric objects. The coordinates and colors of these objects can depend on the values of the variables (both regular and fixed, but not auxiliary) at a given time. The animation then runs through the output of the numerical solution and draws the objects based on that output. I will first list all the commands and then give some examples.

Basically, there are two different types of objects: (i) transient and (ii) permanent. Transient objects have coordinates that are recomputed at every time as they are changing with the output of the simulation. Permanent objects are computed once and are fixed through the duration of the simulation. The objects themselves are simple geometric figures and text that can be put together to form the animation.

Each line in the script file consists of a command or object followed by a list of coordinates that must be separated by semicolons. For some objects, there are other descriptors which can be optional. Since color is important in visualization, there are two ways a color can be described. Either as a formula which is computed to yield a number between 0 and 1 or as an actual color name started with the dollar sign symbol, $. The `ani` file consists of a lines of commands and objects which are loaded into XPP and played back on the animation window. Here are the commands:

  dimension xlo;ylo;xhi;yho

  speed delay

  transient

  permanent

  line x1;y1;x2;y2;color;thickness

  rline x1;y1;color;thickness

  rect x1;y1;x2;y2;color;thickness

  frect x1;y1;x2;y2;color

  circ x1;y1;rad;color;thickness

  fcirc x1;y1;rad;color

  ellip x1;y1;rx;ry;color;thickness

  fellip x1;y1;rx;ry;color

  comet x1;y1;type;n;color

  text x1;y1;s

  vtext x1;y1;s;z

  settext size;font;color

  end

All commands can be abbreviated to their first three letters and case is ignored. At startup the dimension of the animation window in user coordinates is (0,0) at the bottom left and (1,1) at the top right. Thus the point (0.5,0.5) is the center no matter what the actual size of the window on the screen. Color is described by either a floating point number between 0 and 1 with 0 corresponding to red and 1 to violet. When described as a floating point number, it can be a formula that depends on the variables. In all the commands, the color is optional except settext. The other way of describing color is to use names which all start with the $ symbol. The names are: $WHITE, $RED, $REDORANGE, $ORANGE, $YELLOWORANGE, $YELLOW, $YELLOWGREEN, $GREEN, $BLUEGREEN, $BLUE,$PURPLE, $BLACK.

The transient and permanent declarations tell the animator whether the coordinates have to be evaluated at every time or if they are fixed for all time. The default when the file is loaded is transient. Thus, these are just toggles between the two different types of objects.

The number following the speed declaration must be a nonnegative integer. It tells tha animator how many milliseconds to wait between pictures.

The dimension command requires 4 numbers following it. They are the coordinates of the lower left corner and the upper right. The defaults are (0,0) and (1,1).

The settext command tells the animator what size and color to make the next text output. The size must be an integer, { 0,1,2,3,4 } with 0 the smallest and 4 the biggest. The font is either roman or symbol. The color must be a named color and not one that is evaluated.

The remaining ten commands all put something on the screen.

- line x1;y1;x2;y2;color;thickness draws a line from (x1,y1) to (x2,y2) in user coordinates. These four numbers can be any expression that involves variables and fixed variables from your simulation. They are evaluated at each time step (unless the line is permanent) and this is scaled to be drawn in the window. The color is optional and can either be a named color or an expression that is to be evaluated. The thickness is also optional but if you want to include this, you must include the color as well. thickness is any nonnegative integer and will result in a thicker line.

- rline x1;y1;color;thickness is similar to the line command, but a line is drawn from the endpoints of the last line drawn to (xold+x1,yold+y1) which becomes then new last point. All other options are the same. This is thus a ``relative'' line.

- rect x1;y1;x2;y2;color;thickness draws a rectangle with lower corner (x1,y1) to upper corner (x2,y2) with optional color and thickness.

- frect x1;y1;x2;y2;color draws a filled rectangle with lower corner (x1,y1) to upper corner (x2,y2) with optional color.

- circ x1;y1;rad;color;thick draws a circle with radius rad centered at (x1,y1) with optional color and thickness.

- fcirc x1;y1;rad;color draws a filled circle with radius rad centered at (x1,y1) with optional color.

- ellip x1;y1;rx;ry;color draws an ellipse with radii rx,ry centered at (x1,y1) with optional color and thickness.

- fellip x1;y1;rx;ry;color draws a filled ellipse with radii rx,ry centered at (x1,y1) with optional color.

- comet x1;y1;type;n;color keeps a history of the last `n` points drawn and renders them in the optional `color`. If `type` is non-negative, then the last n points are drawn as a line with thickness in pixels of the magnitude of `type`. If `type` is negative, filled circles are drawn with a radius of `-thick` in pixels.

- text x1;y1;s draws a string s at position (x1,y1) with the current color and text properties. Only the coordinates can depend on the current values.

- vtext x1;y1;s;z draws a string s followed by the floating point value z at position (x1,y1) with the current color and text properties. Thus, you can print out the current time or value of a variable at any given time.

REMARK. As with lines in ODE files, it is possible to create arrays of commands using the cobination of the [i1..i2] construction. Some examples are shown below.