Array Ball Question

[Thatguy]

What is it you are trying to achieve?
To get some help my ball array so that all balls will hit the left side of the screen and bounce off the right side


What is the problem you are having?

Well in my code, it shows that each time one ball will hit the right side, another ball will be randomly placed onto the screen and start moving from left to right, i want the balls to move individually after each new addition from right to left, the problem is that if one ball hits the left hand side, then all the other balls will change direction as well; I really want all individual balls to make contact and bounce off the left side

Describe what you have tried to solve this problem

I tried doing for loops to model the movement of all balls but the boundry condition only works for one ball

Post any relevant code (You may choose to attach the file instead of posting the code if it is too long)

Turing:

View.Set ("graphics:1000;500,buttonbar,offscreenonly") var BallRadius : int BallRadius := 12 var BallX : array 1 .. 10 of int % Array of 10 Balls for x position var BallY : array 1 .. 10 of int % Array of 10 Balls, for y position var NumBall : int := 1 randint (BallX (NumBall), 0, maxx) %X Position randint (BallY (NumBall), 0, maxy) %Y Position loop     for i : 1 .. NumBall         drawfilloval (BallX (i), BallY (i), BallRadius, BallRadius, black)         BallX (i) := BallX (i) - 1     end for     View.Update     cls     if BallX (NumBall) = BallRadius             then         loop             for d : 1 .. NumBall                 drawfilloval (BallX (d), BallY (d), BallRadius, BallRadius, black)                 BallX (d) := BallX (d) + 1             end for             View.Update             cls             if BallX (NumBall) = maxx - BallRadius                     then                 NumBall := NumBall + 1                 randint (BallX (NumBall), 0, maxx)     %X Position                 randint (BallY (NumBall), 0, maxy)     %Y Position                 exit             end if         end loop     end if end loop

Please specify what version of Turing you are using
<Answer Here>

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Mod Edit:
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code:

[syntax="turing"] ... code ... [/syntax]

[Zren]

Right now, you only have two areas you are applying "movement" or velocity to the ball positions. The first is in the first for loop, when you move everything left 1 pixel. Once. Then once after a new ball is made. The second time is to move everything right until it hits the right wall.

To have each ball move independantly, each ball must have it's own variable(s) in order to represent what direction it is going. So you'd need another array to represent the horizontal velocity of each ball.

Then you'd do: ballPositionX += ballVelocityX on each frame.

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Since you're about to use more arrays to represent a single object. I should introduce you to records which can help you simplify it all into a single array. Here's an example taken from a simplified particle engine. Note that each "particle" is essentially a "ball".

Turing:

type Vector2D :     record         x, y : int     end record var point : Vector2D point.x := 124 point.y := 534 type Particle :     record         pos : Vector2D % position         vel : Vector2D % velocity     end record var particle : Particle particle.pos.x := 0 particle.pos.y := 0 particle.vel.x := +1 % Right particle.vel.y := 0

Basically, we define our own data type by using records. In the case above, I went beyond that and used our new datatype in another custom datatype. We can even create an array of our new datatype.

Turing:

var particles : array 1 .. 10 of Particle % Init for i : lower (particles) .. upper (particles)     particles (i).pos.x := Rand.Int (0, maxx)     % ... end for View.Set ("graphics;offscreenonly") loop     % Update     for i : lower (particles) .. upper (particles)         % ...         particles (i).pos.y += particles (i).vel.y     end for end loop

If you didn't understand any of that, just ask.

[Thatguy]

I appreciate your help Zren but I am quite a noob at turing. Essentially, I don't really know what record is but I'll look into the tutorials, thanks for your suggestion. If i would need a new array for each position for the ball, would I put that array line of code into both for loops going left and going right? I think I am understanding the general concept, just now sure how to approach it, perhaps you could elaborate a bit more?
Thank You all the same!

[evildaddy911]

you already have arrays for position. what you don't have is arrays defining direction and speed (x and y velocities), which you would declare right after (or before if you wanted) you declare the position arrays. next you want to change this

code:

for i : 1 .. NumBall         drawfilloval (BallX (i), BallY (i), BallRadius, BallRadius, black)         BallX (i) := BallX (i) - 1     end for

to

code:

for i : 1 .. NumBall         drawfilloval (BallX (i), BallY (i), BallRadius, BallRadius, black)         BallX (i) := BallX (i) + BallX_V (i) % instead of hardcoding "-1"     end for

this allows you to set which direction the individual ball is travelling without changing any of the other balls' direction. if you want it to move left, set BallX_V(i) <0. if moving right, BallX_V(i) >0. basicly how you do this is through one big for loop:

code:

% NOTE: this is not working code. this simply explains the steps numBalls : int = 5 Ballx, Bally, BallxV, BallyV :  1 .. numBalls of int % % initialize ball variables % loop     for 1 <= i <= numBalls         drawBall (i) % procedure for drawing ball         Ballx (i) = Ballx (i) + ballxV (i) % move ball horizontally         % move ball vertically         if ballHitsLeft (i) then % if the ball hits the left wall             ballxV (i) = +1 % ball now moves right         end if         %         % check if balls hits right, bottom and top here, using same formula         %     end for end loop

[Thatguy]

evildaddy911, thanks for your suggestion. I made the x velocity an array and used that instead of the -1 . However, my code has not yet changed. I know that this is because my condition for the ball bouncing left and right is only for "NumBall", not all the balls up to NumBall; I am not sure how to set the array of all the balls to be in the condition, but thanks for the velocity array tip, it will be easier to make adjustments if needed. My Code :

Turing:

View.Set ("graphics:1000;500,buttonbar,offscreenonly") var BallRadius : int BallRadius := 12 var BallX : array 1 .. 10 of int % Array of 10 Balls for x position var BallY : array 1 .. 10 of int % Array of 10 Balls, for y position var NumBall : int := 1 randint (BallX (NumBall), 0, maxx) %X Position randint (BallY (NumBall), 0, maxy) %Y Position var BallXV : array 1 .. 10 of int loop     for i : 1 .. NumBall         drawfilloval (BallX (i), BallY (i), BallRadius, BallRadius, black)         BallXV (i) := -1         BallX (i) := BallX (i) + BallXV (i)     end for     View.Update     cls     if BallX (NumBall) = BallRadius             then         loop             for d : 1 .. NumBall                 drawfilloval (BallX (d), BallY (d), BallRadius, BallRadius, black)                 BallXV (d) := 1                 BallX (d) := BallX (d) + BallXV (d)             end for             View.Update             cls             if BallX (NumBall) = maxx - BallRadius                     then                 NumBall := NumBall + 1                 randint (BallX (NumBall), 0, maxx)     %X Position                 randint (BallY (NumBall), 0, maxy)     %Y Position                 exit             end if         end loop     end if end loop

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Mod Edit:
Please wrap you code in either of the following in order to preserve whitespace (indentation) and to highlight the syntax.

code:

[syntax="turing"] ... code ... [/syntax] [code] ... code ... [/code ]

[Zren]

To get collision detection to work for each ball, you need to check each collideable object (each wall), for each ball.

Why not just use a for loop over all ball indexes?

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code:

if BallX (NumBall) = BallRadius then

This code works right now as you only have a velocity of 1. However, if you ever end up having the ball velocity be 2 or some other number, you might skip over where that comparison would ring true.

So for future proofing, you'd do:
ball.x <= leftWallX + ball.radius
or since leftWallX is equivalent to 0:
ball.x <= ball.radius

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Right now, you are breaking out of your game loop to assign the velocity of all the balls. Why not just move that into your game loop like so:

Turing:

View.Set ("graphics:1000;500,buttonbar,offscreenonly") var BallRadius : int BallRadius := 12 var BallX : array 1 .. 10 of int % Array of 10 Balls for x position var BallY : array 1 .. 10 of int % Array of 10 Balls, for y position var NumBall : int := 1 randint (BallX (NumBall), 0, maxx) %X Position randint (BallY (NumBall), 0, maxy) %Y Position var BallXV : array 1 .. 10 of int loop     %...     %View.Update     %cls     %if BallX (NumBall) = BallRadius     %        then     loop         for d : 1 .. NumBall             drawfilloval (BallX (d), BallY (d), BallRadius, BallRadius, black)             BallXV (d) := 1             BallX (d) := BallX (d) + BallXV (d)         end for         View.Update         cls         if BallX (NumBall) = maxx - BallRadius                 then             NumBall := NumBall + 1             randint (BallX (NumBall), 0, maxx)         %X Position             randint (BallY (NumBall), 0, maxy)         %Y Position             % exit             %             for i : 1 .. NumBall                 drawfilloval (BallX (i), BallY (i), BallRadius, BallRadius, black)                 BallXV (i) := -1                 BallX (i) := BallX (i) + BallXV (i)             end for             %         end if     end loop     %end if end loop

The above logic is almost equivalent to what you're doing now.

[Thatguy]

My Code now works thank you for your help. As you have said before this will be for a game, however i am having trouble for collisions. In my game you control a box and you are supposed to avoid the balls. My condition for collision is basically if any of the balls in the array hits the x or y position of the ball, then the game would exit, But it is not working, My code:

Turing:

View.Set ("graphics:1000;500,buttonbar,offscreenonly") var BoxX1, BoxX2, BoxY1, BoxY2, BallRadius, move, BallRand, Color, font1, font2, font3 : int var chars : array char of boolean var chars1, chars2 : char BoxX1 := maxx div 2 BoxX2 := maxx div 2.1 BoxY1 := maxy div 10 BoxY2 := maxy div 8 BallRadius := 12 move := 1 BallRand := Rand.Int (10, 1000) Color := 30 font1 := Font.New ("Comic Sans:30:bold,underline") font2 := Font.New ("Comic Sans:10:underline") font3 := Font.New ("Comic Sans :30:bold") BallRadius := 12 var BallX : array 1 .. 100 of int % Array of 10 Balls for x position var BallY : array 1 .. 100 of int % Array of 10 Balls, for y position var NumBall : int := 1 randint (BallX (NumBall), 0, maxx) %X Position randint (BallY (NumBall), 0, maxy) %Y Position var BallXV : array 1 .. 100 of int BallXV (1) := -1 procedure GameMenu %Creates Game Menu     loop         drawfillbox (0, 0, maxx, maxy, 103)         Font.Draw ("Welcome To The World's Hardest Game", maxx div 7, maxy div 2, font1, red)         Font.Draw ("To Start, Press 'S' ", maxx div 2, maxy div 4, font2, red)         Font.Draw ("To View Controls, Press 'C' ", maxx div 2, maxy div 6, font2, red)         get chars1         if chars1 = ('S')                 then             exit         elsif chars1 = ('C')                 then             drawfillbox (0, 0, maxx, maxy, 103)             Font.Draw ("Controls", maxx div 7, maxy div 1.13, font3, red)             Font.Draw ("The controls are rather simple: Use the cursor keys to move.", 100, 401, font2, red)             Font.Draw ("Avoid any bouncing balls as you will lose one of your 3 lives.", 100, 351, font2, red)             Font.Draw ("Reach The 'CheckPoint' and you will progress into harder levels.", 100, 301, font2, red)             Font.Draw ("If you progress far enough, you will gain the ability to shoot, at which point the 'SPACEBAR' will be the shoot button.", 100, 251, font2, red)             Font.Draw ("Good Luck and Have Fun!", 100, 201, font2, red)             % Font.Draw ("To Return, press 'R'", maxx div 1.5, maxy div 7, font2, red)             Font.Draw ("To Start Press, 'S' ", maxx div 2.3, maxy div 13, font2, red)             View.Update         end if         get chars2         if chars2 = ('S')                 then             exit         elsif chars2 = ('R')                 then             % end if         end if     end loop end GameMenu GameMenu loop     drawfillbox (0, 0, maxx, maxy, 149)     drawfillbox (BoxX1, BoxY1, BoxX2, BoxY2, 31)     for d : 1 .. NumBall         drawfilloval (BallX (d), BallY (d), BallRadius, BallRadius, 31)         BallX (d) := BallX (d) + BallXV (d)         if BallX (d) = maxx - BallRadius                 then             NumBall := NumBall + 1             BallXV (NumBall) := -1             randint (BallX (NumBall), 0, maxx)         %X Position             randint (BallY (NumBall), 0, maxy)         %Y Position             BallXV (d) := -1         elsif                 BallX (d) = BallRadius                 then             BallXV (d) := 1         elsif                 BallX (d) = BoxX1 or BallX (d) = BoxY1 or BallX (d) = BoxX2 or BallX (d) = BoxY2 and BallY(d)=BoxX1 or  BallY(d)=BoxX2 or BallY(d)=BoxY1 or BallY(d)=BoxY2                 then             exit             cls             put "You Lose"         end if     end for     View.Update     cls     %CONTROLS     Input.KeyDown (chars)     if chars (KEY_UP_ARROW) and BoxY2 <= maxy             then         BoxY1 := BoxY1 + 1         BoxY2 := BoxY2 + 1     elsif chars (KEY_DOWN_ARROW) and BoxY1 >= 0             then         BoxY1 := BoxY1 - 1         BoxY2 := BoxY2 - 1     elsif chars (KEY_RIGHT_ARROW) and BoxX1 <= maxx             then         BoxX1 := BoxX1 + 1         BoxX2 := BoxX2 + 1     elsif chars (KEY_LEFT_ARROW) and BoxX2 >= 0             then         BoxX2 := BoxX2 - 1         BoxX1 := BoxX1 - 1     end if     if chars (KEY_LEFT_ARROW) and chars (KEY_UP_ARROW) and BoxX2 >= 0 and BoxY2 <= maxy             then         delay (2)         BoxX2 := BoxX2 - 1         BoxX1 := BoxX1 - 1         BoxY1 := BoxY1 + 1         BoxY2 := BoxY2 + 1     end if     if chars (KEY_RIGHT_ARROW) and chars (KEY_UP_ARROW) and BoxY2 <= maxy and BoxX1 <= maxx             then         delay (2)         BoxX2 := BoxX2 + 1         BoxX1 := BoxX1 + 1         BoxY1 := BoxY1 + 1         BoxY2 := BoxY2 + 1     end if     if chars (KEY_RIGHT_ARROW) and chars (KEY_DOWN_ARROW) and BoxX1 <= maxx and BoxY1 >= 0             then         delay (2)         BoxX2 := BoxX2 + 1         BoxX1 := BoxX1 + 1         BoxY1 := BoxY1 - 1         BoxY2 := BoxY2 - 1     end if     if chars (KEY_LEFT_ARROW) and chars (KEY_DOWN_ARROW) and BoxY1 >= 0 and BoxX2 >= 0             then         delay (2)         BoxX2 := BoxX2 - 1         BoxX1 := BoxX1 - 1         BoxY1 := BoxY1 - 1         BoxY2 := BoxY2 - 1     end if end loop

[Nathan4102]

Your method to find collisions is flawed. Take this image for example:



These two circles are colliding, but their x/y coordinates are not the same. You'll need to find another way to detect collisions.

Hint: If the balls have collided, how close are the two points from each other?

[evildaddy911]

Nathan, he's using a box for the player. that means that he needs a much more complex collision-checking algorithm than the simple "if distance < radSum".

The simplest way to check if a circle is colliding with a rectangle is to check if any of the corners of the rectangle is colliding with the circle. the easiest way to do that is to pretend that the corner is another circle with radius zero. then you use circle-circle collision detection (see situation #1)

Unfortunately, what if the ball is fully inside the square, like in situation #2? what will the method above say?
Note that the center of the circle is fully inside the square. and i'm sure you can figure out how to tell when a point is inside a rectangle

This leads us to situation #3. what if the circle is touching the side of the box, but none of the corners are inside the circle and the center of the circle isn't inside the box either? This is by far the hardest check of the three. There are many ways to solve this problem, but I think that the simplest way is to treat the centerpoint of each side as another corner and use the first method outlined.
The only problem with this solution is what if the ball just touches the rectangle, not getting near enough to any of the 8 "corners?" unfortunately, this method isn't perfect, but is very accurate with smaller rectangles. if the circle's diameter is the same (or larger) as the square's side length, this method will work pretty much all the time.

So, to sum up, first you want to create 8 "collision points." you check if each of these points are within the circle, then, if false, you want to check if the circle's center is inside of the rectangle. The 8-point method does have flaws, but odds are that the collision is going to be caught is the next frame or two, or you won't notice that the collision occurred in the first place.

[Dreadnought]

evildaddy911 wrote:

Nathan, he's using a box for the player. that means that he needs a much more complex collision-checking algorithm than the simple "if distance < radSum".

Not very much more complex...

Take the point in the rectangle with x and y coordinates that are closest to the x and y coordinates of the center of the circle. Check if this point is within the circle.

Here's an example:

Turing:

const DEBUG := true % Set to false to hide the blue dot const RADIUS := 20 const BOX_X1 := 200 const BOX_Y1 := 220 const BOX_X2 := 280 const BOX_Y2 := 260 fcn mid (a, b, c : int) : int     if a > b then         if b > c then             result b         else             result min (a, c)         end if     elsif a > c then         result a     else         result min (b, c)     end if end mid fcn check (cx, cy, r, bx1, by1, bx2, by2 : int) : boolean     var x : int := mid (bx1, cx, bx2)     var y : int := mid (by1, cy, by2)     if DEBUG then         Draw.FillOval (x, y, 3, 3, 9)     end if     result Math.Distance (cx, cy, x, y) <= r end check View.Set ("offscreenonly") loop     var circle_x, circle_y, dummy : int     Mouse.Where (circle_x, circle_y, dummy)     Draw.Box (BOX_X1, BOX_Y1, BOX_X2, BOX_Y2, 7)     if check (circle_x, circle_y, RADIUS, BOX_X1, BOX_Y1, BOX_X2, BOX_Y2) then         Draw.Oval (circle_x, circle_y, RADIUS, RADIUS, 10)     else         Draw.Oval (circle_x, circle_y, RADIUS, RADIUS, 12)     end if     View.Update     cls end loop