learn-physics-examples-0.3: src/eFieldLine2D.hs

{-# OPTIONS_GHC -Wall #-}

module Main where

import Graphics.Gloss
import Physics.Learn.CarrotVec
import Physics.Learn.Position
import Physics.Learn.Curve
import Physics.Learn.Charge
import Physics.Learn.Visual.GlossTools

pixelsPerMeter :: Float
pixelsPerMeter = 40

pixelsPerVPM :: Float
pixelsPerVPM = 5.6

scalePoint :: Float -> Point -> Point
scalePoint m (x,y) = (m*x,m*y)

twoD :: Vec -> Point
twoD r = (realToFrac $ xComp r,realToFrac $ yComp r)

twoDp :: Position -> Point
twoDp r = (realToFrac x, realToFrac y)
    where
      (x,y,_) = cartesianCoordinates r

samplePoints :: [Position]
samplePoints = [cart x y 0 | x <- [-8,-6..8], y <- [-6,-4..6], abs y > 0.5 || abs x > 4.5]

curve1 :: Curve
curve1 = Curve (\t -> cart t 0 0) (-4) 4

eFields :: [(Position,Vec)]
eFields = [(r,eFieldFromLineCharge (const 1e-9) curve1 r) | r <- samplePoints]

arrows :: [Picture]
arrows = [thickArrow 5 (scalePoint pixelsPerMeter $ twoDp r)
                         (scalePoint pixelsPerVPM $ twoD e) | (r,e) <- eFields]

main :: IO ()
main = display (InWindow "Electric Field from a Line Charge" (680,520) (10,10)) white $
       Pictures [(Color blue (Pictures arrows))
                ,Color orange $ Line [(-4*pixelsPerMeter,0),(4*pixelsPerMeter,0)]]