Code: (Select All)
_Title "Mandelbrot Set in QB64PE"
Screen 12
Dim Shared xCenter As Double, yCenter As Double, scale As Double, maxIter As Long
xCenter = -0.5: yCenter = 0: scale = 2: maxIter = 100
Do
Cls
DrawMandelbrot xCenter, yCenter, scale, maxIter
_Limit 120
Select Case _KeyHit
Case 18432: yCenter = yCenter - 0.1 * scale
Case 20480: yCenter = yCenter + 0.1 * scale
Case 19200: xCenter = xCenter - 0.1 * scale
Case 19712: xCenter = xCenter + 0.1 * scale
Case 61, 43: scale = scale / 1.1 '= or +
Case 45, 95: scale = scale * 1.1 '- or _
Case 113, 81: maxIter = maxIter + 10 'q or Q
Case 69, 101: maxIter = maxIter - 10 'e or E
Case 27: System 'ESC
End Select
_Display
Loop
Sub DrawMandelbrot (xCenter As Double, yCenter As Double, scale As Double, maxIter As Long)
Dim As Long x, y
Dim As Double zx, zy, zx2, zy2, cx, cy
Dim As Long iter
For y = 0 To 479
For x = 0 To 639
cx = (x / 320 - 1.5) * scale + xCenter
cy = (y / 240 - 1.0) * scale + yCenter
zx = 0: zy = 0: zx2 = 0: zy2 = 0: iter = 0
Do While (zx2 + zy2 <= 4) And (iter < maxIter)
zy = 2 * zx * zy + cy
zx = zx2 - zy2 + cx
zx2 = zx * zx
zy2 = zy * zy
iter = iter + 1
Loop
If iter = maxIter Then
PSet (x, y), 0
Else
PSet (x, y), iter * 255 / maxIter
End If
Next x
Next y
End Sub
Simple enough to run/test.
Arrow Keys - Pan up / down / left / right.
+ / - - Zoom in / out.
Q / E - Increase / decrease maximum iterations.
