Vector field example.

examples/vector_field.hs

@@ -0,0 +1,66 @@
+#!/usr/bin/env stack
+-- stack --resolver lts-13.14 runghc --package reanimate
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE FlexibleContexts #-}
+module Main (main) where
+
+import           Codec.Picture.Types
+import qualified Data.Colour.Palette.BrewerSet as D
+import qualified Diagrams.Backend.SVG          as D
+import           Diagrams.Prelude              hiding (Animation, boundingBox,
+                                                center, circle, duration,
+                                                fontSize, rotate, scale,
+                                                translate)
+import qualified Diagrams.Prelude              as D
+import qualified Diagrams.TwoD.Path.LSystem    as D
+import           Graphics.SvgTree              (Number (..))
+import           Graphics.SvgTree              as S
+import           Linear.V2
+import           Reanimate.Diagrams
+import           Reanimate.Driver              (reanimate)
+import           Reanimate.LaTeX
+import           Reanimate.Monad
+import           Reanimate.Signal
+import           Reanimate.Svg
+
+
+main :: IO ()
+main = reanimate $ repeatAnimation 5 $ mkAnimation 5 $ do
+    s <- getSignal signalLinear
+    emit $ mkBackground "black"
+    emit $ center $ -- translate (-320/2) (-180/2) $
+      withStrokeColor "white" $
+      renderDiagram $
+        withEnvelope (D.rect 320 180 :: SvgDiagram) $
+        D.scale 50 $
+        lc white $
+        example s
+
+vectorField (x, y) = r2 (sin (y + 1), sin (x + 1))
+
+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