2D Animation/Basic Concept

In this learning resource we create the SIR-Model animation for the learning resource COVID-19.

As a requirement for animation of object in the 2D plane we need:
 * background image and
 * objects that are moving in front of the background

Background Image
A background image can be For the SIR-model in epidemiology we use a vector image as background, because the animation more like an animated diagram with geometric shapes than a snapshot with camera. The background composed of 3 circles in different colors that are representing the epidemioligical state of the people.
 * raster image - e.g. snapshot of a building that is used as background image for the animation.
 * vector image - e.g. for diagrams, flow charts, .... as background
 * (S - Blue Circle) for susceptible people,
 * (I - Red Circle) for infected people,
 * (R - Green Circle) for recovered people.
 * Text elements as part of vector graphics is used to display information about the circle (e.g. "Susceptible"). These text elements can be replaced in the background image e.g. for translation in another language.

Moving Objects
Moving objects are the icons for people. The icons (people) move e.g. from the blue circle (S) for susceptible people towards the red circle (O) for infected people. This movement of objects visualize the infection of susceptible people. If infected people recover the icon moves from the red circle (I) to the green circle for recovered.
 * Red arrow as vector image is used to point at a specific object in the animation.
 * Icon for a person is used to visualize someone is in a specific epidemioligical status.

Generation of the Background Image
The background image can be a snapshot. Then the background will be a raster image. In this case the circle consist of geometrical objects, so the background image is generated as a vector image.
 * (Learning Task) Create the background image in LibreOffice Draw and save that as ODG file format in LibreOffice for further editing or export the background image as SVG-image (Scalable Vector Graphic) for further editing in the OpenSource software InkScape.