ReCode Project - Topographic Form

Topographic Form 1976

Topographic Form recreated

Previously I wrote about the ReCode Project. Today I had a go at another image from the collection, it's not quite pixel perfect but getting pretty close:

import Diagrams.Prelude
import Diagrams.Backend.SVG.CmdLine (defaultMain)

main = defaultMain diagram

diagram = fromVertices zigzag

zigzag = concat $ zipWith line ys (cycle [xs, reverse xs])

line y = map (point y)

point y x = p2 (x, y + heightMap x y)

heightMap x y = maximum
  [ arcH 36   (\t -> t < 0 || pi/2 < t) x y
  , arcH 67.5 (\t -> True)              x y
  , arcH 99   (\t -> -pi/2 < t)         x y
  ]

arcH x0 f x y
  | f t && ri < r && r < ro = h0 * cos (pi * (r - r0) / (ro - ri))
  | otherwise = 0
  where
    t = atan2 y' x'
    r = sqrt $ x'^2 + y'^2
    x' = x - x0
    y' = y - y0

y0 = 40.5
r0 = 15.75
ri = r0 * 0.75
ro = r0 * 1.25
h0 = (ro - ri) / 2
xs = [0 .. 135]
ys = [0 .. 81]

You can download this Haskell source code.