module WindMill
where

import Pan

--
-- Defines a function that is 0 at the origin and has a value between 0 and 1
-- proportial to the distance from the origin. The function has value 1 at
-- distance r from the origin.

circularField r pt =
  let d = distO pt
  in  if d < r then d / r else 1


yellowI :: ImageC
yellowI = lift0 (Col 1 1 0 1)

yellowToBlue :: Frac -> ImageC
yellowToBlue n = lerpI (circularField n) blueI yellowI

bigCircle n = uscale n udisk

smallCircle n = compR $  uscale n udisk

fanRegionPolar :: Int -> PolarRegion
fanRegionPolar numSpokes (Pol r a) = even (floor (a / frac))
  where
    frac = 2*pi / fromIntegral (2*numSpokes)

polarReg :: PolarRegion -> Region
polarReg reg p = reg (toPolar p)

fanRegion :: Int -> Region
fanRegion n = polarReg (fanRegionPolar n)


intersection :: UI Region
intersection = do
  n <- makeISlider "spokes" (3,15) 8
  r1 <- makeSlider "outer radius" (10,100) 30
  r2 <- makeSlider "inner radius" (1,30) 5
  return $ bigCircle r1 `intersectR` smallCircle r2 `intersectR` fanRegion n

croppedYellowToBlue = do
  n <- makeISlider "spokes" (3,15) 8
  r1 <- makeSlider "outer radius" (10,100) 30
  r2 <- makeSlider "inner radius" (1,30) 5
  let intersection = bigCircle r1 `intersectR` smallCircle r2
                                   `intersectR` fanRegion n
  return $ crop intersection (yellowToBlue r1)

effect = do
  cytb <- croppedYellowToBlue
  imageToDisplayFun cytb