Add source files, commit before reverting pictures to lists

This commit is contained in:
jgk
2021-02-15 00:07:55 +01:00
parent c6bcfacc7a
commit 8447844bcd
41 changed files with 13677 additions and 35 deletions
+576
View File
@@ -0,0 +1,576 @@
{-# LANGUAGE BangPatterns #-}
module Geometry
( module Geometry
, module Geometry.Data
)
where
import Geometry.Data
import Data.Function
import Data.List
import Data.Maybe
import Control.Applicative
zeroZ :: Point2 -> Point3
zeroZ (x,y) = (x,y,0)
infixl 6 +.+, -.-
infixl 7 *.*
(+.+) :: Point2 -> Point2 -> Point2
{-# INLINE (+.+) #-}
(x1, y1) +.+ (x2, y2) =
let
!x = x1 + x2
!y = y1 + y2
in (x, y)
(-.-) :: Point2 -> Point2 -> Point2
{-# INLINE (-.-) #-}
(x1, y1) -.- (x2, y2) =
let
!x = x1 - x2
!y = y1 - y2
in (x, y)
(*.*) :: Float -> Point2 -> Point2
{-# INLINE (*.*) #-}
a *.* (x2, y2) =
let
!x = a * x2
!y = a * y2
in (x, y)
infixl 6 +.+.+, -.-.-
infixl 7 *.*.*
(+.+.+) :: Point3 -> Point3 -> Point3
{-# INLINE (+.+.+) #-}
(x1, y1, z1) +.+.+ (x2, y2, z2) =
let
!x = x1 + x2
!y = y1 + y2
!z = z1 + z2
in (x, y, z)
(-.-.-) :: Point3 -> Point3 -> Point3
{-# INLINE (-.-.-) #-}
(x1, y1, z1) -.-.- (x2, y2, z2) =
let
!x = x1 - x2
!y = y1 - y2
!z = z1 - z2
in (x, y, z)
(*.*.*) :: Point3 -> Point3 -> Point3
{-# INLINE (*.*.*) #-}
(x1, y1, z1) *.*.* (x2, y2, z2) =
let
!x = x1 * x2
!y = y1 * y2
!z = z1 * z2
in (x, y, z)
normalizeV :: Point2 -> Point2
{-# INLINE normalizeV #-}
normalizeV p = (1 / magV p) *.* p
angleVV :: Point2 -> Point2 -> Float
{-# INLINE angleVV #-}
angleVV a b = let ma = magV a
mb = magV b
d = a `dotV` b
in acos $ d / (ma * mb)
dotV :: Point2 -> Point2 -> Float
{-# INLINE dotV #-}
dotV (x,y) (z,w) = x*z + y*w
closestPointOnLine :: Point2 -> Point2 -> Point2 -> Point2
{-# INLINE closestPointOnLine #-}
closestPointOnLine a b p
= a +.+ u *.* (b -.- a)
where u = closestPointOnLineParam a b p
closestPointOnLineParam :: Point2 -> Point2 -> Point2 -> Float
{-# INLINE closestPointOnLineParam #-}
closestPointOnLineParam a b p
= (p -.- a) `dotV` (b -.- a) / (b -.- a) `dotV` (b -.- a)
argV :: Point2 -> Float
{-# INLINE argV #-}
argV (x,y) = normalizeAngle $ atan2 y x
detV :: Point2 -> Point2 -> Float
{-# INLINE detV #-}
detV (x1, y1) (x2, y2)
= x1 * y2 - y1 * x2
-- | Angle in radians, anticlockwise from +ve x-axis.
unitVectorAtAngle :: Float -> Point2
{-# INLINE unitVectorAtAngle #-}
unitVectorAtAngle r
= (cos r, sin r)
-- | Rotate a vector by an angle (in radians). +ve angle is counter-clockwise.
rotateV :: Float -> Point2 -> Point2
rotateV r (x, y)
= ( x * cos r - y * sin r
, x * sin r + y * cos r)
{-# INLINE rotateV #-}
-- | Convert degrees to radians
degToRad :: Float -> Float
degToRad d = d * pi / 180
{-# INLINE degToRad #-}
-- | Convert radians to degrees
radToDeg :: Float -> Float
radToDeg r = r * 180 / pi
{-# INLINE radToDeg #-}
-- | Normalize an angle to be between 0 and 2*pi radians
normalizeAngle :: Float -> Float
normalizeAngle f = f - 2 * pi * floor' (f / (2 * pi))
where floor' :: Float -> Float
floor' x = fromIntegral (floor x :: Int)
{-# INLINE normalizeAngle #-}
-- the following helper draws a rectangle based on maximal N E S W values
rectNESW :: Float -> Float -> Float -> Float -> [Point2]
rectNESW a b c d = [(b,a),(b,c),(d,c),(d,a)
]
rectNSEW n s e w = rectNESW n e s w
rectNSWE :: Float -> Float -> Float -> Float -> [Point2]
rectNSWE n s w e = [ (w,n), (w,s), (e,s), (e,n)]
-- -- the following filters points in a polygon: supposes the points in the
-- polygon are listed in anticlockwise order
pointInOrOnPolygon :: Point2 -> [Point2] -> Bool
pointInOrOnPolygon p (x:xs) = all (\l -> not (uncurry isRHS l p)) $ zip (x:xs) (xs ++ [x])
pointInPolygon :: Point2 -> [Point2] -> Bool
pointInPolygon p [] = False
pointInPolygon p (x:xs) = all (\l -> uncurry (errorIsLHS 1) l p) $ zip (x:xs) (xs ++ [x])
errorPointInPolygon :: Int -> Point2 -> [Point2] -> Bool
errorPointInPolygon i p xs | length xs == 1 = error "one point polygon"
| length xs == 2 = error "two point polygon"
| nub xs == xs = pointInPolygon p xs
| otherwise = error $ "errorPointInPolygon "++ show i
errorNormalizeV :: Int -> Point2 -> Point2
errorNormalizeV i (0,0) = error $ "problem with function: errorNormalizeV "++show i
errorNormalizeV i p = normalizeV p
errorAngleVV :: Int -> Point2 -> Point2 -> Float
errorAngleVV i (0,0) _ = error $ "problem with function: errorAngleVV "++show i
errorAngleVV i _ (0,0) = error $ "problem with function: errorAngleVV "++show i
errorAngleVV i p p' = angleVV p p'
errorIsLHS :: Int -> Point2 -> Point2 -> Point2 -> Bool
errorIsLHS i x y | x == y = error $ "problem with function: errorIsLHS "
++show i
| otherwise = isLHS x y
errorClosestPointOnLine :: Int -> Point2 -> Point2 -> Point2 -> Point2
errorClosestPointOnLine i x y | x == y = error $ "problem with function: errorClosestPointOnLine "
++show i
| otherwise = closestPointOnLine x y
errorClosestPointOnLineParam :: Int -> Point2 -> Point2 -> Point2 -> Float
errorClosestPointOnLineParam i x y z | x == y = dist x z
-- error $ "problem with function: errorClosestPointOnLineParam " ++show i
| otherwise = closestPointOnLineParam x y z
safeNormalizeV :: Point2 -> Point2
safeNormalizeV (0,0) = (0,0)
safeNormalizeV p = normalizeV p
-- tests whether a point is on the LHS of a line
-- this has been called somewhere with l1 == l2
isLHS :: Point2 -> Point2 -> Point2 -> Bool
{-# INLINE isLHS #-}
isLHS' l1 l2 p | l1 == l2 = False
| otherwise = closestPointOnLineParam l1 (l1 +.+ vNormal (l2 -.- l1)) p < 0
isLHS (x,y) (x',y') (x'',y'')
| (x,y) == (x',y') = False
| otherwise = a1 * b2 - a2 * b1 > 0
where a1 = x' - x
a2 = y' - y
b1 = x'' - x
b2 = y'' - y
isRHS :: Point2 -> Point2 -> Point2 -> Bool
{-# INLINE isRHS #-}
isRHS (x,y) (x',y') (x'',y'')
| (x,y) == (x',y') = False
| otherwise = a1 * b2 - a2 * b1 < 0
where a1 = x' - x
a2 = y' - y
b1 = x'' - x
b2 = y'' - y
--isRHS l1 l2 p = closestPointOnLineParam l1 (l1 +.+ vNormal (l2 -.- l1)) p > 0
-- reorders points to be anticlockwise around their center
orderPolygon :: [Point2] -> [Point2]
orderPolygon [] = []
orderPolygon ps = sortBy (compare `on` \p -> argV (p -.- cen)) ps
where cen = 1/ fromIntegral (length ps) *.* foldr1 (+.+) ps
vNormal :: Point2 -> Point2
{-# INLINE vNormal #-}
vNormal (x,y) = (y,-x)
vInverse :: Point2 -> Point2
vInverse (x,y) = (-x,-y)
dist :: Point2 -> Point2 -> Float
{-# INLINE dist #-}
dist p1 p2 = magV (p2 -.- p1)
normV :: Point2 -> Point2
{-# INLINE normV #-}
normV (0,0) = (0,0)
normV p = (1/magV p ) *.* p
magV :: Point2 -> Float
{-# INLINE magV #-}
magV (x,y) = sqrt $ x^2 + y^2
pHalf :: Point2 -> Point2 -> Point2
pHalf a b = 0.5 *.* (a +.+ b)
linGrad :: (Eq a,Fractional a) => (a,a) -> (a,a) -> Maybe a
linGrad (x,y) (a,b) | x-a == 0 = Nothing
| otherwise = Just $ (y-b)/(x-a)
axisInt :: (Eq a,Fractional a) => (a,a) -> (a,a) -> Maybe a
axisInt p (a,b) = pure b ^-^ (pure a ^*^ linGrad p (a,b))
where (^-^) = liftA2 (-)
(^*^) = liftA2 (*)
-- intersectSegSeg is sometimes broken-- the following fixes at least some of
-- the cases
-- it is, however, slow
myIntersectSegSeg a@(ax,ay) b@(bx,by) c@(cx,cy) d@(dx,dy) = case ratIntersectLineLine a b c d of
Nothing -> Nothing
Just (x,y) -> if inbetween x && inbetween' y
then Just (x,y)
else Nothing
where inbetween x = ((ax <= x && x <= bx) || (bx <= x && x <= ax)) &&
((cx <= x && x <= dx) || (dx <= x && x <= cx))
inbetween' y = ((ay <= y && y <= by) || (by <= y && y <= ay)) &&
((cy <= y && y <= dy) || (dy <= y && y <= cy))
crossV :: Point2 -> Point2 -> Float
crossV (ax,ay) (bx,by) = ax*by - ay*bx
myIntersectLineLine :: (Eq a,Fractional a) => (a,a) -> (a,a) -> (a,a) -> (a,a) -> Maybe (a,a)
myIntersectLineLine a@(ax,ay) b c@(cx,cy) d
| linGrad a b == Nothing = fmap ((,) ax) $ axisInt (c *-* (ax,0)) (d *-* (ax,0))
| linGrad c d == Nothing = fmap ((,) cx) $ axisInt (a *-* (cx,0)) (b *-* (cx,0))
| otherwise
= case linGrad a b ^-^ linGrad c d of
Just 0 -> Nothing
_ -> liftA2 (,) newx
((linGrad a b ^*^ newx) ^+^ axisInt a b)
where (^-^) = liftA2 (-)
(^+^) = liftA2 (+)
(^/^) = liftA2 (/)
(^*^) = liftA2 (*)
newx = (axisInt c d ^-^ axisInt a b) ^/^ (linGrad a b ^-^ linGrad c d)
(*-*) (ax,ay) (bx,by) = (ax-bx,ay-by)
ratIntersectLineLine :: Point2 -> Point2 -> Point2 -> Point2 -> Maybe Point2
ratIntersectLineLine a b c d = fmap toNumPoint2 $ myIntersectLineLine (toRatPoint2 a) (toRatPoint2 b) (toRatPoint2 c) (toRatPoint2 d)
where toRatPoint2 (x,y) = (toRational x, toRational y)
toNumPoint2 (x,y) = (fromRational x, fromRational y)
f = toRatPoint2 . roundPoint2
roundPoint2 :: Point2 -> Point2
roundPoint2 (x,y) = (fromIntegral $ round x,fromIntegral $ round y)
circOnLine' :: Point2 -> Point2 -> Point2 -> Float -> Bool
circOnLine' p1 p2 c rad = isJustTrue (fmap (\p -> magV (p -.- c) < rad) y)
where y = intersectSegLine' p1 p2 c (c +.+ vNormal (p1 -.- p2))
isJustTrue (Just True) = True
isJustTrue _ = False
circOnLine :: Point2 -> Point2 -> Point2 -> Float -> Bool
circOnLine p1 p2 c rad = magV (p1 -.- c) <= rad || magV (p2 -.- c) <= rad
|| isJustTrue (fmap (\p -> magV (p -.- c) < rad) y)
where y = intersectSegLine' p1 p2 c (c +.+ vNormal (p1 -.- p2))
isJustTrue (Just True) = True
isJustTrue _ = False
difference x y | x > y = x - y
| otherwise = y - x
reflectIn :: Point2 -> Point2 -> Point2
reflectIn line vec = let angle = 2 * angleBetween line vec
in rotateV angle vec
angleBetween v1 v2 = argV v1 - argV v2
doublePair :: (a,a) -> [(a,a)]
doublePair (x,y) = [(x,y),(y,x)]
polysIntersect :: [Point2] -> [Point2] -> Bool
polysIntersect (p:ps) (q:qs)
= any isJust $ (\(a,b) (c,d) -> myIntersectSegSeg a b c d) <$> pairs1 <*> pairs2
where pairs1 = zip (p:ps) (ps++[p])
pairs2 = zip (q:qs) (qs++[q])
anyPolyssIntersect :: [[Point2]] -> [[Point2]] -> Bool
anyPolyssIntersect x y = or $ polysIntersect <$> x <*> y
nRays :: Int -> [Point2]
nRays n = take n $ iterate (rotateV (2*pi/fromIntegral n)) $ (600,0)
nRaysRad :: Int -> Float -> [Point2]
nRaysRad n x = take n $ iterate (rotateV (2*pi/fromIntegral n)) $ (x,0)
-- angles go from 0 to 2pi, need to work out what is left of another
isLeftOfA :: Float -> Float -> Bool
isLeftOfA angle1 angle2 = (angle1 - angle2 < pi && angle1 > angle2)
|| (angle2 - angle1 > pi && angle2 > angle1)
isLeftOf :: Point2 -> Point2 -> Bool
isLeftOf x y = isLeftOfA (argV x) (argV y)
-- diffAngles has an issue...
diffAngles :: Float -> Float -> Float
diffAngles x y | diff > pi = diffAngles (x - 2*pi) y
| diff >= 0 = diff
| diff > -pi = -diff
| otherwise = diffAngles (x + 2*pi) y
where diff = x-y
differenceAngles = diffAngles
angleDifference = diffAngles
-- given a triangle where we know the length of a first side,
-- the length of a second side, and the angle between the first side and the
-- third side, finds the length of the third side
-- not this doesn't necessarily find ALL solutions, asin is a map not a function
ssaTri :: Float -> Float -> Float -> Float
ssaTri ab bc a
| sin a == 0 = 0
| bc == 0 = ab
| otherwise = let c = asin ( (ab * (sin a))/bc)
b = pi - (a + c)
in sin b * bc / sin a
-- fix points: we now fix the triangle in the coordinate system, and return a
-- third unknown point:
-- the point which lies between pa and pc' on a line from b of length bc
-- note that there are likely two such points, this seems to return the point
-- closer to pc'
ssaTriPoint :: Point2 -> Point2 -> Point2 -> Float -> Point2
ssaTriPoint pa pb pc' bc
= let ab = magV (pa -.- pb)
a = errorAngleVV 6 (pb -.- pa) (pc' -.- pa)
ac = ssaTri ab bc a
in pa +.+ (ac *.* errorNormalizeV 47 (pc' -.- pa))
-- the above SHOULD return a Maybe Point...
ssaTriPoint' :: Point2 -> Point2 -> Point2 -> Float -> Maybe Point2
ssaTriPoint' pa pb pc' bc
| dist pb (closestPointOnSeg pa pc' pb) >= bc
= Nothing
| otherwise
= Just $ ssaTriPoint pa pb pc' bc
ssaTriPointCorrect :: Point2 -> Point2 -> Point2 -> Float -> Maybe Point2
ssaTriPointCorrect pa pb pc' bc
| param <= 1 && param >= 0 = Just p
| otherwise = Nothing
where p = ssaTriPoint pa pb pc' bc
param = closestPointOnLineParam pa pc' p
closestPointOnSeg :: Point2 -> Point2 -> Point2 -> Point2
closestPointOnSeg segP1 segP2 p
| errorClosestPointOnLineParam 3 segP1 segP2 p <= 0 = segP1
| errorClosestPointOnLineParam 4 segP1 segP2 p >= 1 = segP2
| otherwise = errorClosestPointOnLine 2 segP1 segP2 p
pointInCircle :: Point2 -> Float -> Point2 -> Maybe Point2
pointInCircle p r c | p == c = Just p
| magV (p -.- c) < r = Just p
| otherwise = Nothing
--determines if a moving point intersects with a circle,
--if so, returns a point on circle that intersects with the line passing
--throught the circle : HOPEFULLY THE CORRECT OF THE TWO!
collidePointCirc :: Point2 -> Point2 -> Float -> Point2 -> Maybe Point2
collidePointCirc p1 p2 rad c = ssaTriPoint' p2 c p1 rad
-- changes the point to a measure of the distance
collidePointCirc' :: Point2 -> Point2 -> Float -> Point2 -> Maybe Float
collidePointCirc' p1 p2 rad c = fmap (\x -> magV (x -.- p1))
(collidePointCirc p1 p2 rad c)
--returns both the point and the measure of the distance
collidePointCirc'' :: Point2 -> Point2 -> Float -> Point2 -> Maybe (Point2,Float)
collidePointCirc'' p1 p2 rad c = (,) <$> collidePointCirc p1 p2 rad c
<*> collidePointCirc' p1 p2 rad c
collidePointCircCorrect :: Point2 -> Point2 -> Float -> Point2 -> Maybe Point2
collidePointCircCorrect p1 p2 rad c = ssaTriPointCorrect p2 c p1 rad
-- finds the height of a triangle using herons formula
-- the base is the line between the first two points
heron :: Point2 -> Point2 -> Point2 -> Float
heron x y z | x == y = 0
| otherwise = let a = magV $ x -.- y
b = magV $ y -.- z
c = magV $ z -.- x
s = (a+b+c)/2
area = sqrt(s*(s-a)*(s-b)*(s-c))
in 2*area/a
-- multiplies reflection in normal by factor
reflectInParam :: Float -> Point2 -> Point2 -> Point2
reflectInParam x line vec = let angle = 2 * angleBetween line vec
rAng = rotateV angle vec
p = x *.* errorClosestPointOnLine 3 (0,0) (vNormal line) rAng
in rAng -.- p
reflectIn' :: Point2 -> Point2 -> Point2 -> Point2 -> Point2
reflectIn' l1 l2 v1 v2 = v1 +.+ reflectIn (l1 -.- l2) (v2 -.- v1)
isOnLine :: Point2 -> Point2 -> Point2 -> Bool
isOnLine l1 l2 p = errorClosestPointOnLineParam 10 l1 (l1 +.+ vNormal (l2 -.- l1)) p == 0
&& errorClosestPointOnLineParam 11 l1 l2 p <= 1
&& errorClosestPointOnLineParam 12 l1 l2 p >= 0
-- the take 5000 here is a hack, otherwise divideLine seems to sometimes
-- generate an infinite list, and I don't know why
divideLine :: Float -> Point2 -> Point2 -> [Point2]
--divideLine x a b = map (\i -> a +.+ (i / (fromIntegral numPoints)) *.* (b -.- a))
divideLine x a b = take 5000 $ map (\i -> a +.+ (i / (fromIntegral numPoints) *.* (b -.- a)) )
$ map fromIntegral ns
where d = dist a b
numPoints = max 1 $ ceiling $ d / x
ns = [0 .. numPoints]
-- pulled the following from the haskell wiki
bresenham :: (Int,Int) -> (Int,Int) -> [(Int,Int)]
{-# INLINE bresenham #-}
bresenham pa@(xa,ya) pb@(xb,yb) = map maySwitch . unfoldr go $ (x1,y1,0)
where
steep = abs (yb - ya) > abs (xb - xa)
maySwitch = if steep then (\(x,y) -> (y,x)) else id
[(x1,y1),(x2,y2)] = sort [maySwitch pa, maySwitch pb]
deltax = x2 - x1
deltay = abs (y2 - y1)
ystep = if y1 < y2 then 1 else -1
go (xTemp, yTemp, error)
| xTemp > x2 = Nothing
| otherwise = Just ((xTemp, yTemp), (xTemp + 1, newY, newError))
where
tempError = error + deltay
(newY, newError) = if (2*tempError) >= deltax
then (yTemp+ystep,tempError-deltax)
else (yTemp,tempError)
divideCircle :: Float -> Point2 -> Float -> [Point2]
divideCircle x cen rad = map (cen +.+) $ nPointsOnCirc n rad
where n = ceiling $ rad * 2 * pi / x
nPointsOnCirc :: Int -> Float -> [Point2]
nPointsOnCirc n rad = take n $ iterate (rotateV (2*pi/fromIntegral n)) $ (rad,0)
lineInPolygon :: Point2 -> Point2 -> [Point2] -> Bool
lineInPolygon a b ps = pointInPolygon a ps || pointInPolygon b ps
|| any (isJust . uncurry (intersectSegSeg' a b)) pss
where pss = zip ps (tail ps ++ [head ps])
--intersectSegLineFrom :: Point2 -> Point2 -> Point2 -> Point2 -> Maybe Point2
--intersectSegLineFrom a b c d
-- = case intersectSegLine a b c d of
-- Just p | closestPointOnLineParam c d p >= 0 -> Just p
-- | otherwise -> Nothing
-- Nothing -> Nothing
intersectSegSeg' :: Point2 -> Point2 -> Point2 -> Point2 -> Maybe Point2
{-# INLINE intersectSegSeg' #-}
intersectSegSeg' (x1,y1) (x2,y2) (x3,y3) (x4,y4)
-- | t' < 0 || u' < 0 || t' > den || u' > den || den == 0
-- = Nothing
| den == 0 = Nothing
| den > 0 && (t' < 0 || u' < 0 || t' > den || u' > den)
= Nothing
| den < 0 && (t' > 0 || u' > 0 || t' < den || u' < den)
= Nothing
-- | den > 0 && (t' < 0 || t' > den)
-- = Nothing
-- | den < 0 && (t' > 0 || t' < 0-den)
-- = Nothing
| otherwise = Just (x1 + (x2-x1)*t'/den, y1 + (y2-y1)*t'/den)
where
den = (x1-x2)*(y3-y4) - (y1-y2)*(x3-x4)
t' = (x1-x3)*(y3-y4) - (y1-y3)*(x3-x4)
u' = (y1-y2)*(x1-x3) - (x1-x2)*(y1-y3)
intersectSegLineFrom' :: Point2 -> Point2 -> Point2 -> Point2 -> Maybe Point2
{-# INLINE intersectSegLineFrom' #-}
intersectSegLineFrom' (x1,y1) (x2,y2) (x3,y3) (x4,y4)
-- | t' < 0 || u' < 0 || t' > den || u' > den || den == 0
-- = Nothing
| den == 0 = Nothing
| den > 0 && ( t' < 0 || u' < 0 || t' > den )
= Nothing
| den < 0 && ( t' > 0 || u' > 0 || t' < den )
= Nothing
-- | den > 0 && (t' < 0 || t' > den)
-- = Nothing
-- | den < 0 && (t' > 0 || t' < 0-den)
-- = Nothing
| otherwise = Just (x1 + (x2-x1)*t'/den, y1 + (y2-y1)*t'/den)
where
den = (x1-x2)*(y3-y4) - (y1-y2)*(x3-x4)
t' = (x1-x3)*(y3-y4) - (y1-y3)*(x3-x4)
u' = (y1-y2)*(x1-x3) - (x1-x2)*(y1-y3)
intersectSegLine' :: Point2 -> Point2 -> Point2 -> Point2 -> Maybe Point2
{-# INLINE intersectSegLine' #-}
intersectSegLine' (x1,y1) (x2,y2) (x3,y3) (x4,y4)
-- | t' < 0 || u' < 0 || t' > den || u' > den || den == 0
-- = Nothing
| den == 0 = Nothing
| den > 0 && (t' < 0 || t' > den)
= Nothing
| den < 0 && (t' > 0 || t' < den)
= Nothing
-- | den > 0 && (t' < 0 || t' > den)
-- = Nothing
-- | den < 0 && (t' > 0 || t' < 0-den)
-- = Nothing
| otherwise = Just (x1 + (x2-x1)*t'/den, y1 + (y2-y1)*t'/den)
where
den = (x1-x2)*(y3-y4) - (y1-y2)*(x3-x4)
t' = (x1-x3)*(y3-y4) - (y1-y3)*(x3-x4)
u' = (y1-y2)*(x1-x3) - (x1-x2)*(y1-y3)
intersectLineLine' :: Point2 -> Point2 -> Point2 -> Point2 -> Maybe Point2
{-# INLINE intersectLineLine' #-}
intersectLineLine' (x1,y1) (x2,y2) (x3,y3) (x4,y4)
| den == 0 = Nothing
| otherwise = Just (x1 + (x2-x1)*t'/den, y1 + (y2-y1)*t'/den)
where
den = (x1-x2)*(y3-y4) - (y1-y2)*(x3-x4)
t' = (x1-x3)*(y3-y4) - (y1-y3)*(x3-x4)