Public Class Form1
    Private Const LP = 20000  '計算回数
    Private MID As Integer   '確率指定数 - 1 (DP, PROPの最大添え字)
    Private PROP() As Double '確率累積
    Dim img As New Bitmap(300, 300) '300x300サイズのImage
    '------------------ ぶどうの葉 ---------------------------------
    'Private Const SCX = 200   'X方向描画スケール
    'Private Const SCY = -200  'Y方向描画スケール
    'Private Const XMIN = 0    '左座標
    'Private Const YMIN = 200  '上座標
    'Private DP() As Double = {0.5, 0.168, 0.166, 0.166} '確率
    'Private Fun(,,) As Double = { _
    '    {{0.8, 0.0, 0.1}, {0.0, 0.8, 0.04}}, _
    '    {{0.5, 0.0, 0.25}, {0.0, 0.5, 0.4}}, _
    '    {{0.355, -0.355, 0.266}, {0.355, 0.355, 0.078}}, _
    '    {{0.355, 0.355, 0.378}, {-0.355, 0.355, 0.434}} _
    '}
    '------------------ シダの葉 ---------------------------------
    'Private Const SCX = 200   'X方向描画スケール
    'Private Const SCY = -200  'Y方向描画スケール
    'Private Const XMIN = 0    '左座標
    'Private Const YMIN = 200  '上座標
    'Private DP() As Double = {0.73, 0.13, 0.13, 0.01} '確率
    'Private Fun(,,) As Double = { _
    '   {{0.856, 0.0414, 0.07}, {-0.0205, 0.858, 0.147}}, _
    '   {{0.244, -0.385, 0.393}, {0.176, 0.244, 0.102}}, _
    '   {{-0.144, 0.39, 0.527}, {0.181, 0.259, -0.014}}, _
    '   {{0.0, 0.0, 0.486}, {0.355, 0.216, 0.05}} _
    '}
    '------------------ アンモナイト ---------------------------------
    'Private Const SCX = 100   'X方向描画スケール
    'Private Const SCY = -100  'Y方向描画スケール
    'Private Const XMIN = 100    '左座標
    'Private Const YMIN = 100  '上座標
    'Private DP() As Double = {0.06, 0.02, 0.92} '確率
    'Private Fun(,,) As Double = { _
    '   {{-0.29, 0, 0.59}, {0, 0.2, -0.32}}, _
    '   {{-0.07, -0.02, 0.79}, {-0.01, 0.29, -0.06}}, _
    '   {{0.94, -0.22, -0.05}, {0.21, 0.96, 0.01}} _
    '}
    '------------------ 樹木 ---------------------------------
    Private Const SCX = 100   'X方向描画スケール(樹木）
    Private Const SCY = -100  'Y方向描画描画スケール
    Private Const XMIN = 100  '左座標
    Private Const YMIN = 200  '上座標
    Private DP() As Double = {0.1, 0.2, 0.2, 0.2, 0.2, 0.1} '確率
    Private Fun(,,) As Double = { _
        {{0.05, 0.0, 0.0}, {0.0, 0.6, 0.0}}, _
        {{0.05, 0.0, 0.0}, {0.0, -0.5, 1.0}}, _
        {{0.46, -0.32, 0.0}, {0.39, 0.38, 0.6}}, _
        {{0.47, -0.15, 0.0}, {0.17, 0.42, 1.1}}, _
        {{0.43, 0.28, 0.0}, {-0.25, 0.45, 1.0}}, _
        {{0.42, 0.26, 0.0}, {-0.35, 0.31, 0.7}} _
    }
    Private Sub 累積確率設定()
        MID = DP.Length - 1 : ReDim PROP(MID)
        Dim S As Double = 0
        For i = 0 To MID
            S = S + DP(i) : PROP(i) = S
        Next
    End Sub
    Private Function setID() As Integer
        Dim i As Integer, S As Double = Rnd()
        For i = 0 To MID
            If S < PROP(i) Then Return i
        Next
        Return MID
    End Function
    Private Sub 描画(X As Double, Y As Double)
        Dim IX As Integer = X * SCX + XMIN + 0.5
        Dim IY As Integer = Y * SCY + YMIN + 0.5
        If IX >= 0 And IX < img.Width And IY >= 0 And IY < img.Height Then
            img.SetPixel(IX, IY, Color.DarkGreen)
        End If
    End Sub
    Private Function setFun(ID As Integer, Row As Integer, X As Double, Y As Double)
        Return Fun(ID, Row, 0) * X + Fun(ID, Row, 1) * Y + Fun(ID, Row, 2)
    End Function
    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim X1 As Double, Y1 As Double, X2 As Double = 0, Y2 As Double = 0
        Dim ID As Integer, k As Integer
        Dim g As Graphics = Graphics.FromImage(img) : g.Clear(Color.White) '描画クリア
        累積確率設定() : Randomize()
        For k = 1 To LP
            X1 = X2 : Y1 = Y2 : ID = setID()
            X2 = setFun(ID, 0, X1, Y1) : Y2 = setFun(ID, 1, X1, Y1)
            描画(X2, Y2)
        Next
        PictureBox1.Image = img : g.Dispose() 'リソースを解放する
    End Sub
End Class