Interactive applications have many coordinate systems

• Our shape is drawn in Normalized Device Coordinates (NDCs)
  • \([-1,1]\) in both the \(x-\) and \(y-\)dimensions
• Mouse moving in window coordinates
  • \([0,width] \times [0,height]\) measured in pixels
• Need to convert input coordinates into the appropriate space
  • NDCs for this application
  • many different scenarios (e.g., 3D space for flight simulation)