[bb] Midpoint Displacement Algorithm by Pakz [ 1+ years ago ]

[BlitzBot]

Title : Midpoint Displacement Algorithm
Author : Pakz
Posted : 1+ years ago

Description :

I found this code more then 10 years ago and used it a couple of times after converting it from c++ I think. I converted it to Blitz, java and back to blitz just yet. I hope I did not break it.

The code makes heightmaps.

Code :

Code: BlitzBasic

1. ; Midpoint Displacement
2. Graphics 640,480,32,2
3. SetBuffer BackBuffer()
4.  
5. Global mapwidth = 100
6. Global mapheight = 100
7. Dim map(mapwidth,mapheight)
8.  
9. domidpoint
10. tw = GraphicsWidth()/mapwidth
11. th = GraphicsHeight()/mapheight
12. For y=0 To mapheight
13. For x=0 To mapwidth
14.         Color map(x,y),map(x,y),map(x,y)
15.         Rect x*tw,y*th,tw,th,True
16. Next
17. Next
18.  
19. Flip
20. WaitKey
21. End
22.  
23. ; Here the midpoint code begins.
24. Function domidpoint()
25.   ; Erase the old map array..
26.   For y = 0 To mapheight
27.   For x = 0 To mapwidth
28.     map(x,y)=0
29.   Next
30.   Next
31.   ; Setup points in the 4 corners of the map.
32.   map(0,0) = 128
33.   map(mapwidth,0) = 128
34.   map(mapwidth,mapheight) = 128
35.   map(0,mapheight) = 128
36.   ; Do the midpoint
37.   midpoint(0,0,mapwidth,mapheight)
38. End Function
39.  
40.  ; This is the actual Mid point displacement code.
41.  Function midpoint(x1,y1,x2,y2)
42.         ; If this is pointing at just on pixel, Exit because
43.         ; it doesn't need doing}
44.         If x2-x1<2 And y2-y1<2 Then Return False
45.  
46.         ; Find distance between points And
47.         ;use when generating a random number.
48.     dist=(x2-x1+y2-y1)
49.     hdist=dist / 2
50.         ;Find Middle Point
51.     midx=(x1+x2) / 2
52.     midy=(y1+y2) / 2
53.         ;Get pixel colors of corners
54.     c1=map(x1,y1)
55.     c2=map(x2,y1)
56.     c3=map(x2,y2)
57.     c4=map(x1,y2)
58.  
59.         ; If Not already defined, work out the midpoints of the corners of
60.         ; the rectangle by means of an average plus a random number.
61.     If(map(midx,y1)=0) Then map(midx,y1)=((c1+c2+Rand(dist)-hdist) / 2)
62.     If(map(midx,y2)=0) Then map(midx,y2)=((c4+c3+Rand(dist)-hdist) / 2)
63.     If(map(x1,midy)=0) Then map(x1,midy)=((c1+c4+Rand(dist)-hdist) / 2)
64.     If(map(x2,midy)=0) Then map(x2,midy)=((c2+c3+Rand(dist)-hdist) / 2)
65.  
66.         ; Work out the middle point...
67.     map(midx,midy) = ((c1+c2+c3+c4+Rand(dist)-hdist)/4)
68.  
69.         ; Now divide this rectangle into 4, And call again For Each smaller
70.         ; rectangle
71.     midpoint(x1,y1,midx,midy);
72.     midpoint(midx,y1,x2,midy);
73.     midpoint(x1,midy,midx,y2);
74.     midpoint(midx,midy,x2,y2);
75.  
76. End Function

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