[bb] Collision2.0 - Motion based, very accurate. by AntonyWells [ 1+ years ago ]

[BlitzBot]

Title : Collision2.0 - Motion based, very accurate.
Author : AntonyWells
Posted : 1+ years ago

Description : This lib lets you check for collisions with much greater accuracy than blitz's current method.
As it will register collisions even if images pass over each wholey. (I.e if you're ship as moving at 25 pixels and in one frames goes over a 12 pixel image completely, this lib will still register the collision)

It does this by generating(In hardware) motion maps for each collision object, and then performing just the single col check as per normal for a standard test.

InitCol(res) lets you set the resolution of the motion maps. Smaller =less accurate but faster.
id=CreateCol(image) creates a collision object. Create one for every image.

Then to update it, just call moveCol(col,x,y) once per frame.

And that's it, just checkCol(col1,col2) and it'll return true if they have collided, even if they moved 600 pixels in one frame.

CheckCol has a skip rate...The higher the skip rate the faster the motion map generation, but the less accurate it'll be.

The example code will work with any image, but just delete it when you need the lib for your project.

there's a little demo in there..just hit left mouse button..it draws the two motion maps on the top left hand corner of the screen. And it tells when a collision has occured.

Code :

Code: BlitzBasic

1. ;-quick example
2.  
3. initcol(64) ;init system with 64pixel motion map
4.  
5. col1=createCol(myImage) create a col image.call this once for each unique image.
6.  
7. moveCol(col1,20,20) ;move it. call this once per frame.
8.  
9. and finally,
10.  
11. checkCol(col1,col2,rate) to check for a collision.
12. rate= skip rate, see above.
13.  
14.  
15. ;-[=-]
16. Type cSys
17.         Field mRes,iRes
18.         Field xs#,ys#
19.         Field gw#,gh#
20. End Type
21. Type col
22.         Field id,mMap ;low res version and motion map.
23.         Field lx#,ly#,x#,y#
24. End Type
25.  
26.  
27. Global cSys.cSys
28. Function initCols(mRes=256)
29.         cSys=New cSys
30.         csysmRes=mRes
31.         cSysiRes=iRes
32.         cSysgw=GraphicsWidth()
33.         cSysgh=GraphicsHeight()
34.         TFormFilter False
35. End Function
36. Function createCol(image)
37.         col.col=New col
38.         colid=CopyImage(image)
39.         colmMap=CreateImage(csysmRes,csysmres)
40.         wd#=Float(ImageWidth(image))/Float(GraphicsWidth())
41.         hd#=Float(ImageHeight(image))/Float(GraphicsHeight())
42.         nw#=csysmres*wd
43.         nh#=csysmres*hd
44.         ResizeImage colid,nw,nh
45.         Return Handle(col)
46. End Function
47.  
48. Function moveCol(col,x#,y#) ;move it to the same x,y as the image
49.         in.col=Object.col(col)
50.         inlx=inx
51.         inly=iny
52.         inx=x
53.         iny=y
54. End Function
55.  
56. Function checkCol(col1,col2,skipRate=5) ;higher skip rate = faster but less accurate.Play with it, diff shapes will fair differantly
57.         c1.col=Object.col(col1)
58.         If c1=Null Return
59.         c2.col=Object.col(col2)
60.         If c2=Null Return
61.         ;-
62.         ;-[ Generate motion maps]
63.         genMotionMap(c1,skipRate)
64.         genMotionMap(c2,skipRate)
65.         Return ImagesCollide(c1mmap,0,0,0,c2mmap,0,0,0)
66. End Function
67.  
68. Function genMotionMap(in.col,skip=1) ;INTERNAL FUNCTION -
69.         ax#=inx
70.         ay#=iny
71.         ex#=inlx
72.         ey#=inly
73.         ax=csysmres*(ax/csysgw)
74.         ay=csysmres*(ay/csysgh)
75.         ex=csysmres*(ex/csysgw)
76.         ey=csysmres*(ey/csysgh) ;scale coords into the res of the motion map
77.        
78.         xd#=ex-ax
79.         yd#=ey-ay
80.         If Abs(xd)>Abs(yd) steps#=Abs(xd) Else steps#=Abs(yd)
81.         xi#=xd/Steps
82.         yi#=yd/Steps
83.         SetBuffer ImageBuffer(inmMap)
84.         sImg=inid
85.         xi=xi*Float(skip)
86.         yi=yi*Float(skip)
87.         Cls
88.         If steps<1 steps=1
89.         Repeat
90.                         ;-
91.                         DrawImage sImg,ax,ay
92.                         ax=ax+xi
93.                         ay=ay+yi
94.                 ;-
95.                 steps=steps-skip
96.         Until steps<1
97. End Function

Comments :


Rck(Posted 1+ years ago)

 missing comment statements dude, run your code first then do a clean copy-paste next time


Q(Posted 1+ years ago)

 ^What he said.