Unit 3 - Symmetry and Regularity

In this unit, students learn how to combine rotations and scalings with translations and overlays, and how the order of transformations effects the outcome. Rotations provide a way to decompose pictures with axial symmetry and scalings provide ways to decompose pictures with horizontal or vertical mirror symmetries. In the clock exercise, students need to use all four operations (overlays, translations, rotations and scalings) to place the numbers at the proper place in the dial.

Students also learn about the RGB and HSL color representations, and about using functions to transform colors. Finally, they also learn about alpha compositing of images as a technique to emulate transparency.

Unit objectives

  • Demonstrate how to use rotations and scalings to decompose objects with axial or mirror symmetries
  • Design rules for calculating layouts that follow symmetric patterns that repeat
  • Describe the RGB and the HSL representations of colors
  • Demonstrate the use of alpha compositing to create translucid colors