Optical pattern. Computer model of patterns formed by bending a coloured transparent sheet. The flat structure is distorted, as seen by the distortion of the gridlines. Viewing the distortion from this angle shows areas of overlap (darker) and actual fold lines. The colours have also been modified to reflect the distortion of the sheet. This pattern is an example of caustics, the patterns arising when overlap is observed. This model was created as an artwork by Professor Eric Heller.