hglmandel/04_Mandelbulb/Mandelbulb.lhs
2012-05-10 16:50:44 +02:00

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## Cleaning the code
The first thing to do is to separate the GLUT/OpenGL
part from the computation of the shape.
Here is the cleaned version of the preceeding section.
Most boilerplate was put in external files.
- [`YBoiler.hs`](code/YBoiler.hs), the 3D rendering
- [`Mandel`](code/Mandel.hs), the mandel function
- [`ExtComplex`](code/ExtComplex.hs), the extended complexes
> import YBoiler -- Most the OpenGL Boilerplate
> import Mandel -- The 3D Mandelbrot maths
>
> -- yMainLoop takes two arguments
> -- the title of the window
> -- a function from time to triangles
> main :: IO ()
> main = yMainLoop "3D Mandelbrot" (\_ -> allPoints)
>
> nbDetails = 200 :: GLfloat
> width = nbDetails
> height = nbDetails
> deep = nbDetails
>
> depthPoints :: [ColoredPoint]
> depthPoints = do
> x <- [-width..width]
> y <- [0..height]
> let
> neighbors = [(x,y),(x+1,y),(x+1,y+1),(x,y+1)]
> depthOf (u,v) = findMaxOrdFor (ymandel u v) 0 deep 7
> -- zs are 3D points with found depth
> zs = map (\(u,v) -> (u,v,depthOf (u,v))) neighbors
> -- ts are 3D pixels + mandel value
> ts = map (\(u,v,w) -> (u,v,w,ymandel u v (w+1))) zs
> -- ps are 3D opengl points + color value
> ps = map (\(u,v,w,c') ->
> (u/width,v/height,w/deep,colorFromValue c')) ts
> -- If the point diverged too fast, don't display it
> if (and $ map (\(_,_,_,c) -> c>=57) ts)
> then []
> -- Draw two triangles
> else [ps!!0,ps!!1,ps!!2,ps!!0,ps!!2,ps!!3]
>
> allPoints :: [ColoredPoint]
> allPoints = planPoints ++ map inverseDepth planPoints
> where
> planPoints = depthPoints ++ map inverseHeight depthPoints
> inverseHeight (x,y,z,c) = (x,-y,z,c)
> inverseDepth (x,y,z,c) = (x,y,-z+1/deep,c)
>
> findMaxOrdFor func minval maxval 0 = (minval+maxval)/2
> findMaxOrdFor func minval maxval n =
> if (func medpoint) /= 0
> then findMaxOrdFor func minval medpoint (n-1)
> else findMaxOrdFor func medpoint maxval (n-1)
> where medpoint = (minval+maxval)/2
>
> colorFromValue n =
> let
> t :: Int -> GLfloat
> t i = 0.7 + 0.3*cos( fromIntegral i / 10 )
> in
> ((t n),(t (n+5)),(t (n+10)))
>
> ymandel x y z = mandel (2*x/width) (2*y/height) (2*z/deep) 64