Translate the vertex centroid to the origin, rotate, and translate back:
rotatePoly :: Polygon -> Double -> Polygon
rotatePoly ps theta =
  (translate c . map turn . translate (-cx,-cy)) ps
  where
    c@(cx,cy) = centroid ps
    turn (x,y) = (cos theta*x + sin theta*y,
                 -sin theta*x + cos theta*y)
This follows the supplied rotation matrix, so positive rotates clockwise in the usual Cartesian axes. The opposite signs give the conventional counterclockwise matrix. Since the vertex centroid of the centered vertices is zero and a linear map commutes with their average, the final centroid remains c.

Ancestors (11)

  1. 4
  2. Functional programming, design and analysis of algorithms (resit)
  3. 2016
  4. Past exam of the year 1 of the computer science course of the University of Oxford
  5. Year 1 of the computer science course of the University of Oxford
  6. Computer science course of the University of Oxford
  7. Undergraduate course of the University of Oxford
  8. Course of the University of Oxford
  9. University of Oxford
  10. List of universities
  11. Home

View article source

Discussion (0) New discussion

There are no discussions about this article yet.

Articles by others on the same topic (0)

There are currently no matching articles.
See all articles in the same topic Create my own version