forest-dojo.fsx

open System
open System.Drawing
open System.Windows.Forms


// Create a form to display the graphics
let width, height = 1000, 1000         
let form = new Form(Width = width, Height = height)
let box = new PictureBox(BackColor = Color.White, Dock = DockStyle.Fill)
let image = new Bitmap(width, height)
let graphics = Graphics.FromImage(image)
//The following line produces higher quality images, 
//at the expense of speed. Uncomment it if you want
//more beautiful images, even if it's slower.
//Thanks to https://twitter.com/AlexKozhemiakin for the tip!
graphics.SmoothingMode <- System.Drawing.Drawing2D.SmoothingMode.HighQuality
let brush = new SolidBrush(Color.FromArgb(0, 0, 0))

box.Image <- image
form.Controls.Add(box) 

// Compute the endpoint of a line
// starting at x, y, going at a certain angle
// for a certain length. 
let endpoint x y angle length =
    x + length * cos angle,
    y + length * sin angle

let flip x = (float)height - x

// Utility function: draw a line of given width, 
// starting from x, y
// going at a certain angle, for a certain length.
let drawLine (target : Graphics) (brush : SolidBrush) 
             (x : float) (y : float) 
             (angle : float) (length : float) (width : float)
             (color: Color) =
    use brush2 = new SolidBrush(color)
    let x_end, y_end = endpoint x y angle length
    let origin = new PointF((single)x, (single)(y |> flip))
    let destination = new PointF((single)x_end, (single)(y_end |> flip))
    let pen = new Pen(brush2, (single)width)
    target.DrawLine(pen, origin, destination)

let draw x y angle length width color = 
    drawLine graphics brush x y angle length width color

let pi = Math.PI

// Now... your turn to draw
// The trunk
//draw 250. 50. (pi*(0.5)) 100. 4.
//let x, y = endpoint 250. 50. (pi*(0.5)) 100.
//// first and second branches
//draw x y (pi*(0.5 + 0.3)) 50. 2.
//draw x y (pi*(0.5 - 0.4)) 50. 2.
let random = System.Random()

//let drawTree angle1Delta angle2Delta iterations = 
let rec tree x y angle length width length1Div length2Div length3Div angle1Delta angle2Delta angle3Delta =
    if length < 1.5 then ()
    else
        let r = (random.Next(200/int length))
        let g = (random.Next(200/int length))
        let b = (random.Next(200/int length))
        let color = Color.FromArgb(r, g, b)
        draw x y (pi*angle) length width color
        let x', y' = endpoint x y (pi*angle) length
        let chaosAngle1 = (random.NextDouble()*2. - 1.)/10.
        let chaosAngle2 = (random.NextDouble()*2. - 1.)/10.
        let chaosAngle3 = (random.NextDouble()*2. - 1.)/10.
        tree x' y' (angle + (angle1Delta + chaosAngle1)) (length*length1Div) (width*length1Div) length1Div length2Div length3Div angle1Delta angle2Delta angle3Delta 
        tree x' y' (angle + (angle2Delta + chaosAngle2)) (length*length2Div) (width*length2Div) length1Div length2Div length3Div angle1Delta angle2Delta angle3Delta 
        tree x' y' (angle + (angle2Delta + chaosAngle3)) (length*length3Div) (width*length3Div) length1Div length2Div length3Div angle1Delta angle2Delta angle3Delta 
//tree 250. 50. (pi*(0.5)) 100. 4. iterations

let rec forest numberOfTrees = 
    if numberOfTrees = 0 then ()
    else
        let startX, startY = (random.Next(width/2)+250, 200+random.Next(height/3))

        let startLength = (random.Next(200) + 20)
        let randDouble lower upper = random.NextDouble()*(upper-lower)+lower
        let start1LengthDiv = randDouble 0.3 0.75
        let start2LengthDiv = randDouble 0.3 0.55
        let start3LengthDiv = randDouble 0.3 0.75
        let chunk = 1. + random.NextDouble()*7.

        tree (float startX) (float startY) (0.5) (float startLength) chunk start1LengthDiv start2LengthDiv start3LengthDiv 0.3 -0.2 0.1 
        forest (numberOfTrees-1)

forest 20

form.ShowDialog()

(* To do a nice fractal tree, using recursion is
probably a good idea. The following link might
come in handy if you have never used recursion in F#:
http://en.wikibooks.org/wiki/F_Sharp_Programming/Recursion
*)