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Diagrams.hs
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Diagrams.hs
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{-# LANGUAGE Arrows #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE NoMonomorphismRestriction #-}
-- |
-- Copyright : (c) Ivan Perez, 2018-2022
-- License : BSD-style (see the LICENSE file in the distribution)
-- Maintainer : ivan.perez@keera.co.uk
--
-- Example of connecting the diagrams drawing library with Yampa.
--
-- Based on:
-- https://archives.haskell.org/projects.haskell.org/diagrams/gallery/VectorField.html
--
-- Install diagrams with Cairo support, together with Yampa:
--
-- cabal sandbox init
-- cabal install Yampa diagrams -fcairo
--
-- Compile in a sandbox with:
--
-- cabal exec -- ghc --make examples/Diagrams.hs
--
-- And run with:
--
-- ./examples/Diagrams -w 400 -h 400 -o output.gif
import Diagrams.Backend.Cairo.CmdLine
import Diagrams.Prelude
import FRP.Yampa hiding (norm, ( # ), (*^))
main = mainWith $ take 60 frames
frames :: [(Diagram B, Int)]
frames = zip ((embed sfVF $ deltaEncode 1 $ repeat ())) (repeat 1)
sfVF :: SF () (Diagram B)
sfVF = proc () -> do
t <- time -< ()
let diag = ( field t # translateY 0.05 # lc white
<> ( square 3.5 # lw none # alignBL))
returnA -< diag
field t = position $ zip points (arrows t)
locs = [(x, y) | x <- [0.1, 0.3 .. 3.25], y <- [0.1, 0.3 .. 3.25]]
points = map p2 locs
vectorField t (x, y) = r2 (sin (t + y + 1), sin (t + x + 1))
arrows t = map (arrowAtPoint t) locs
arrowAtPoint t (x, y) = arrowAt' opts (p2 (x, y)) (sL *^ vf) # alignTL
where
vf = vectorField t (x, y)
m = norm $ vectorField t (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)