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demo_stars: use fold, give names

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This commit is contained in:
Alexander Gudev 2025-01-18 15:34:53 +02:00
commit 06456c44a0
1 changed files with 13 additions and 13 deletions
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26
examples/demo_stars.hs
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@ -30,12 +30,12 @@ main = reanimate $ scene $ do
starAnimation :: Animation
starAnimation = mkAnimation 10 $ \t ->
let camZ = t * 4
in withStrokeWidth 0 $ rotate (t * 360) $ mkGroup
[ translate (x / newZ) (y / newZ) $ dot (1 - newZ)
| (x, y, z) <-
reverse $ take nStars $ dropWhile (\(_, _, z) -> z < camZ) allStars
, let newZ = z - camZ
]
dropInvisible = dropWhile $ \(_, _, z) -> z < camZ
placeDot (x, y, z) =
let newZ = z - camZ
in translate (x / newZ) (y / newZ) $ dot (1 - newZ)
starSVGs = map placeDot . reverse . take nStars . dropInvisible $ allStars
in withStrokeWidth 0 $ rotate (t * 360) $ mkGroup starSVGs
where
black = PixelRGB8 0x0 0x0 0x0
dot o =
@ -52,15 +52,15 @@ trails trailDur raw = mkAnimation (duration raw) $ \t ->
in construct $ reverse [idx - trailFrames .. idx]
where
fps = 200
construct [] = mkGroup []
construct (x : xs) = mkGroup
[ withGroupOpacity (fromIntegral trailFrames / fromIntegral (trailFrames + 1))
$ construct xs
, getFrame x
]
construct :: [Int] -> SVG
construct = foldl' go (mkGroup []) where
go acc idx = mkGroup $ [reduceOpacity acc, getFrame idx]
reduceOpacity = withGroupOpacity (fromIntegral trailFrames / fromIntegral (trailFrames + 1))
getFrame idx = frames V.! (idx `mod` nFrames)
trailFrames = round (trailDur * fps)
nFrames = round (duration raw * fps)
getFrame idx = frames V.! (idx `mod` nFrames)
frames = V.fromList
[ frameAt (fromIntegral i / fromIntegral nFrames * duration raw) raw
| i <- [0 .. nFrames]