[bmx] Circle Circle Instersection Points by Haramanai [ 1+ years ago ]

[BlitzBot]

Title : Circle Circle Instersection Points
Author : Haramanai
Posted : 1+ years ago

Description : It's not my code and it's just a translation of a java code in BlitzMax
All credits go here

    Circle Intersection
    By William Ngan (http:/www.metaphorical.net)
    Processing BETA code (http://www.processing.org)

Code :

Code: BlitzMax

1. Rem
2.         Circle Intersection
3.          By William Ngan (http:/www.metaphorical.net)
4.          Processing BETA code (http://www.processing.org)
5. End Rem
6.  
7. Type Circle
8.  
9.         Field x, y, r, r2
10.  
11.         Function create:Circle( px#, py#, pr# )
12.                 Local Circle_:Circle = New Circle
13.                 Circle_.x = px
14.                 Circle_.y = py
15.                 Circle_.r = pr
16.                 Circle_.r2 = pr*pr
17.                 Return Circle_
18.         End Function
19.  
20. End Type
21.  
22.  
23. Function intersect( cA:Circle , cB:Circle )
24.  
25.         Local dx# = cA.x - cB.x
26.         Local  dy# = cA.y - cB.y
27.         Local  d2# = dx*dx + dy*dy
28.         Local  d# = Sqr( d2 )
29.  
30.         If  d>cA.r+cB.r Or d<Abs(cA.r-cB.r) Return'; // no solution
31.        
32.  
33.         Local a# = (cA.r2 - cB.r2 + d2) / (2*d)
34.         Local h# = Sqr( cA.r2 - a*a )
35.         Local x2# = cA.x + a*(cB.x - cA.x)/d
36.         Local y2# = cA.y + a*(cB.y - cA.y)/d
37.  
38.  
39.         DrawRect( x2, y2, 5, 5 )
40.  
41.         Local paX% =  x2 + h*(cB.y - cA.y)/d
42.         Local paY% =  y2 - h*(cB.x - cA.x)/d
43.         Local pbX# = x2 - h*(cB.y - cA.y)/d
44.         Local pbY# = y2 + h*(cB.x - cA.x)/d
45.         DrawText pax , 10 , 10
46.         DrawRect paX , PaY , 5 , 5
47.         DrawRect pbX , PbY , 5 , 5
48.  
49. End Function
50.  
51. Function DrawCircle(R:Circle)
52.         DrawOval R.x - R.r  , R.y - R.r , R.r*2 , R.r*2
53. End Function
54.  
55. Local Cir:Circle = Circle.create(10 , 10 , 100)
56. Local Cir2:Circle = Circle.create(100 , 100 , 50)
57.  
58. Graphics 640 , 480 , 0
59.  
60. While Not KeyDown(Key_Escape)
61.         Cls
62.         SetColor 255 , 0 , 0
63.         drawCircle(Cir)
64.         SetColor 0 , 255 , 0
65.         drawCircle(Cir2)
66.         SetColor 0 , 0 , 255
67.         intersect(cir , cir2)
68.         Cir.X = MouseX()
69.         Cir.Y = MouseY()
70.         Flip
71.         FlushMem
72. Wend

Comments :


Haramanai(Posted 1+ years ago)

 And just a function

Code: [Select]


Function Circle_Circle_intersect(paX# Var , paY# Var , pbX# Var , pbY# Var , x1# , y1# , r1# , x2# , y2# , r2#)


Local dx# = x1 - x2
Local  dy# = y1 - y2
Local  d2# = dx*dx + dy*dy
Local  d# = Sqr( d2 )

If  d>r1+r2 Or d<Abs(r1-r2) Then Return False'; // no solution


Local a# = (r1*r1 - r2*r2 + d2) / (2*d)
Local h# = Sqr( r1*r1 - a*a )
Local rx2# = x1 + a*(x2 - x1)/d
Local ry2# = y1 + a*(y2 - y1)/d


paX# =  rx2 + h*(y2 - y1)/d
paY# =  ry2 - h*(x2 - x1)/d
pbX# = rx2 - h*(y2 - y1)/d
pbY# = ry2 + h*(x2 - x1)/d

Return True

End Function



Bobysait(Posted 1+ years ago)

 we maybe could optimise using simple previous test:

Code: [Select]

Function intersect( cA:Circle , cB:Circle )
Local R0:Float=cA.r+cB.r
Local dx:Float=cA.x - cB.x
' no solution ------------------
If Abs(dx)>R0 Return False
Local dy:Float=cA.y - cB.y
If Abs(dy)>R0 Return False
Local  d2# = dx*dx + dy*dy
If d2>R0*R0 Return False
Local R_:Float=cA.r-cB.r
If d2<R_*R_ Return False
' ------------------------------
Local  d# = Sqr( d2 )
[...]
End Function