reanimate-0.2.0.0: examples/vector_field.hs

#!/usr/bin/env stack
-- stack runghc --package reanimate
{-# LANGUAGE FlexibleContexts #-}
module Main (main) where

main :: IO ()
main = return ()
{-
import           Diagrams.Prelude              hiding (Animation, boundingBox,
                                                center, circle, duration,
                                                fontSize, rotate, scale,
                                                translate)
import qualified Diagrams.Prelude              as D
import           Reanimate.Diagrams
import           Reanimate hiding ((#))


main :: IO ()
main = reanimate $ repeatA 5 $ mkAnimation 5 $ \t ->
    mkGroup
    [ mkBackground "black"
    , scale (2/50) $ center $ -- translate (-320/2) (-180/2) $
      withStrokeColor "white" $
      renderDiagram $
        withEnvelope (D.rect 320 180 :: SvgDiagram) $
        D.scale 50 $
        lc white $
        example t ]

vectorField :: (Double, Double) -> V2 Double
vectorField (x, y) = r2 (sin (y + 1), sin (x + 1))

arrowAtPoint :: (Double, Double) -> SvgDiagram
arrowAtPoint (x, y) = arrowAt' opts (p2 (x, y)) (sL *^ vf) # alignTL
  where
    vf   = vectorField (x, y)
    m    = norm $ vectorField (x, y)

-- Head size is a function of the length of the vector
-- as are tail size and shaft length.

    hs   = 0.02 * m
    sW   = 0.004 * m
    sL   = 0.05 + 0.1 * m
    opts = (with & arrowHead  .~ spike
                 & headLength .~ normalized hs
                 & shaftStyle %~ lwN sW)

example :: Double -> SvgDiagram
example n = field
  where
    xOffset = cos (2*pi*n)
    yOffset = sin (2*pi*n)
    locs   = [(x+xOffset, y+yOffset) | x <- [0.1, 0.3 .. 3.25], y <- [0.1, 0.3 .. 3.25]]

    points = map p2 locs

    arrows = map arrowAtPoint locs
    field   = position $ zip points arrows
-}