Square and Circle collision detection not working proporly

[Offroadrider]

Hey guys,

I am trying to make a tag program but the collision detection between the circle and the square is not working proporly.

Here is the code that is not working

Turing:

%Variables var ballx, bally :int :=300 var boxx,boxy :int :=50 var chars :array char of boolean var font1,font2,font3 :int var colour1, colour2 :int :=0 var z :int font1 := Font.New ("timesnewroman:50:bold") font2 := Font.New ("timesnewroman:100:bold") font3 := Font.New ("timesnewroman:15") randint (z, 0, 1) if z = 0 then  colour1 := 40  end if if z = 1 then  colour2 := 40  end if     View.Set ("offscreenonly") loop Input.KeyDown (chars) drawfillbox (maxx,maxy,0,0,black) drawfilloval (ballx,bally,10,10, colour1) drawfillbox (boxx,boxy,boxx +20,boxy +20, colour2) View.Update %%%%%%%%CONTROLS%%%%%%%%%%% %%%%%%%%%%%%P1%%%%%%%%%%%%% if chars (KEY_UP_ARROW) then     bally +=2     end if if chars (KEY_DOWN_ARROW) then     bally -=2     end if if chars (KEY_RIGHT_ARROW) then     ballx +=2     end if if chars (KEY_LEFT_ARROW) then     ballx -=2     end if %%%%%%%%%%%%P2%%%%%%%%%%%%%% if chars ('w') then     boxy +=2     end if if chars ('s') then     boxy -=2     end if if chars ('a') then     boxx -=2     end if if chars ('d') then     boxx +=2     end if     %%%%%%%%%%%boundries%%%%%%%% if bally > 380 then     bally := 380     end if if bally < 20 then     bally := 20     end if if ballx > 620 then     ballx := 620     end if if ballx < 20 then     ballx := 20     end if     if boxy > 360 then     boxy := 360     end if if boxy < 0 then     boxy := 0     end if if boxx > 600 then     boxx := 600     end if if boxx < 0 then     boxx := 0     end if     %%%%%%%%%taging%%%%%%%%%%%% if colour1=40 and ballx -20 < boxx and bally -20 > boxy and ballx < boxx +20 and bally > boxy +20 then     colour2 := 40     colour1 := 0     end if     if colour2=40 and boxx +20 > ballx and boxy < bally and boxy + 20 > bally and boxx < ballx then     colour1 := 40     colour2 := 0     end if       if chars (' ') then     exit     end if end loop

This is in turing 4.1.1

1 more thing,
this is not the entire code
it would be way too big for this space.
this is just the pieces of code that have to do with the collision detection

Thanks for your help

[Insectoid]

Quote:

bally -20 > boxy

Quote:

bally > boxy +20

What's different about these two statements?

[Offroadrider]

Nothing, it's just that when i wrote the ballx-20, it finnaly worked on the some what on y-axis if I put boxx +20 > ballx like on the other line, it didn't work

[Offroadrider]

feel free to copy the code into a turing file to help find out what's not working

[Zren]

Box:
The bottom left is (boxx, boxy).
The top right is (boxx+20, boxy+20)

Circle:
The middle is (ballx, bally)

Circle and rectangular collision is done with if a point is within the range of the circle or rectangle. You seem to be trying to compare two ranges. And also treating the ball's center point like one of the rectangles control points (it's in the middle not a corner).

Make sure your code follows this pattern, where p is the middle of your ball.

Rectangle:
box.x <= p.x <= box.x + box.width
box.y <= p.y <= box.y + box.height

The way collision detection works, is that you can check circle against circle, or rectangle against rectangle, or if a point is within either. You can't easily check collision between a circle and a rectangle. You can however treat a circle as a rectangle since the circle can fit inside a rectangle (easier and more accurate than putting the rectangle inside the circle).

This post on collision detection should help:
http://compsci.ca/v3/viewtopic.php?t=13661