taper.hs

taperGeometric
  :: Double
  -- ^ percentage to decrease by each iteration
  -> Double
  -- ^ Starting width
  -> [V2 Double]
  -- ^ The path
  -> [(V2 Double, Double)]
  -- ^ The path, augmented with line widths
taperGeometric percentage startingWidth path = zip path widths
 where
 -- TODO: Probably want to use DList here? But can easily just reverse the path for now
  widths = iterate (* percentage) startingWidth

-- left biased
taperedPair (v, s) (u, t) = (LineSegment v u, s)

renderSketch :: Generate ()
renderSketch = do
  fillScreenHsv charcoal

  let rects' = flip map ((,) <$> [0,20..80] <*> [0,20..80]) $ \(x,y) -> Rect x y 20 20

  rects <- shuffleM rects'

  for_ (zip [3..] rects) $ \(n, rect) -> do
    path <- chaikinN 5 <$> replicateM n (genPointIn (scaleRect 0.8 rect))

    let
      tapered = taperGeometric 0.99 1 path

    cairo $ setLineCap LineCapRound

    for_ (pairsWith taperedPair tapered) $ \(segment, size) -> do
      cairo $ do
        setLineWidth size
        drawLineSegment segment
        setSourceHsv (lighten (1 - size) linen) *> stroke