circular collision

[Saad85]

sorry if its come up before, but how would i go about creating a program that mimics circular collision/angular collision?

[Tony]

You start by reading the [Turing Tutorials], in order of Turing Walkthrough

[Albrecd]

Use Trig functions (sin, cosin, etc.)

[Cervantes]

A collision occurs between two circles if the distance between their centres is less than or equal to the sum of their radii. To determine the distance between their centres, use Math.Distance.

code:

if Math.Distance (circle1.x, circle1.y, circle2.x, circle2.y) <= circle1.radius + circle2.radius then     %collision end if

Math.Distance requires Turing v4.0.5 or newer. If you don't have this, you'll have to make your own distance function, which is very easy.

As for the motion of the circles after collision, you should examine this source code, by thoughtful.

[Martin]

BUT to make things interesting, notice that if they're moving fast enough just checking their distance apart every frame won't be good enough - they'll pass right through each other.

[Tony]

Martin -- I don't remember how you ended up fixing that issue. Do you remember where the thread was?

[Martin]

http://www.compsci.ca/v2/viewtopic.php?t=9706

I don't have the source anymore, unfortunately. I think I'll rewrite it this weekend though.

[Saad85]

k, obviously i wasn't clear enough. i know how to tell if they've collided, how do i make 2 circles bounce off each other as they would in real life (instead of just reversing x and y velocities)


this is my attempt at it.. it didnt go too well so dont bother analysing my code in detail. the basic idea is to store the previous frame's coordinates and use that to find angle of incidence, which i then use to find the next frame's coordinates. this i then use to find velocities. my code is obviously flawed in more ways than 1 so i wont bother going into detail about it.

code:

setscreen("offscreenonly") var defang:real               %angle after deflection %big circle var c1x,c1y:real:=200 var c1vx,c1vy:real var c1r:int:=70 %small circle var c2px,c2py,prevd:real%          < previous var c2x,c2y:real:=100 var c2vx, c2vy:real var c2r:int:=20 var c2nx,c2ny:real%                   < next procedure movement  %                       draw  drawfilloval(round(c1x),round(c1y),c1r,c1r,red)  drawfilloval(round(c2x),round(c2y),c2r,c2r,blue)  c2px:=c2x  c2py:=c2y    c1x+=c1vx  c1y+=c1vy  if c1x>=maxx-c1r then c1vx:=-1*abs(c1vx) c1x:=maxx-c1r end if  if c1x<=c1r then c1vx:=abs(c1vx) c1x:=c1r end if  if c1y>=maxy-c1r then c1vy:=-1*abs(c1vy) c1y:=maxy-c1r end if  if c1y<=c1r then c1vy:=abs(c1vy) c1y:=c1r end if    c2x+=c2vx  c2y+=c2vy  if c2x>=maxx-c2r then c2vx:=-1*abs(c2vx) c2x:=maxx-c2r end if  if c2x<=c2r then c2vx:=abs(c2vx) c2x:=c2r end if  if c2y>=maxy-c2r then c2vy:=-1*abs(c2vy) c2y:=maxy-c2r end if  if c2y<=c2r then c2vy:=abs(c2vy) c2y:=c2r end if end movement procedure collision  if sqrt( (c2x-c1x)**2 + (c2y-c1y)**2)<=c1r+c2r then %<----collision   defang:=arctand((c2y-c1y)/(c2x-c1x))-arctand((c2py-c1y)/(c2px-c1x))+arctand((c2y-c1y)/(c2x-c1x))   prevd:=sqrt((c2px-c1x)**2 + (c2py-c1y)**2)      if c2x>=c1x and c2y>=c1y then     defang+=0    elsif c2x<c1x and c2y>c1y then     defang:=180-defang    elsif c2x<=c1x and c2y<=c1y then     defang:=180+defang    elsif c2x>c1x and c2y<c1y then     defang:=0-defang    end if     c2nx:=c1x+prevd*cos(defang)   c2ny:=c1y+prevd*sin(defang)     c2vx:=(c2x-c2nx)/15%      <  new velocities   c2vy:=(c2y-c2ny)/15%      <      end if end collision c1vx:=Rand.Int(-1,1)%<----------------| c1vy:=Rand.Int(-1,1)%                 | %                                     |--circle velocities c2vx:=Rand.Int(1,4)%                  | c2vy:=Rand.Int(1,4)%<-----------------| loop  movement  collision    View.Update  cls  delay(15) end loop

if anyone would help me out with this, it would be appreciated

[Saad85]

sorry for double post, but where it says

c2vx:=(c2x-c2nx)/15
c2vy:=(c2y-c2ny)/15

i did not (at first) include the /15 in there but for some reason the balls start going REALLY fast if its not in there so i just did it to slow them down (couldnt find the problem)

[[Gandalf]]

Re-read Cervantes' last post, with an emphasis on the ending.

[Martin]

For the actual collisions -
http://en.wikipedia.org/wiki/Elastic_collision

[MysticVegeta]

Guys your are excluding Andy completely from this topic! What about the whatdotcolor collision, not everyone has 4.0.5

[md]

why would you use whatdotcolor when the mathematical way is so much better? Especially when you don't need 4.05 (at least I'm fairly certain you don't... math functions are present in all version IIRC; though perhaps not vector stuff).

[Cervantes]

Agreed. whatdotcolour is assuredly not the way to go. Turing v4.0.5 has the Math.Distance function which is useful to this, though ideally you would heed Martin's comments and do some more advanced math. Regardless, Turing v4.0.5 is not necessary for the mathematical approach.

[MysticVegeta]

what about versions 4.0.5 less, they dont have Math.Distance...