Need some help with some collision detection

[aspire]

Hey everyone. I am back with some more questions.

Well, at the moment I am really lost lol. I need to make a pong game.
So far this is what I have

* A moving ball
* A movable paddle
* Boundarys for the ball


This is what I need some help with/cant figure out what/how to apply it with/

* Make the ball bounce off the paddle


So far here is what I have:
**Couldnt remember what the turing tags were at the time I posted this, have to look them up lol**

Turing:

setscreen ("graphics:vga") var X, Y : int := 105 var DX, DY : int := 1 var KEY : string (1) var chars : string (1) var left, right : int var leftr, rightr : int := 1 left := 100 right := 200 locate (3, 9) put "Score" locate (3, 25) put "Lives" loop     % Boundary     drawbox (50, 50, 600, 350, 9)     % The Ball Draws     drawfilloval (X, Y, 5, 5, 9)     % Paddle Draws     drawfillbox (left, 50, right, 65, 7)     delay(5)     % Ball Erases     drawfilloval (X, Y, 5, 5, 0)     % Paddle Erases     drawfillbox (left, 50, right, 65, 0)         % Ball Boundarys     X := X + DX     Y := Y + DY     if X = 56 or X = 594 then         DX := (-1) * DX     end if     if Y = 56 or Y = 344 then         DY := (-1) * DY     end if     % Paddle Boundarys     if left = 50 then         leftr := (-1) * leftr     elsif right = 594 then         rightr := (-1) * rightr     end if     % The keyboard controls     if hasch then         getch (chars)         if ord (chars) = 203 and left > 50 then             left := left - 10             right := right - 10         elsif                 ord (chars) = 205 and right < 600 then             right := right + 10             left := left + 10         end if     end if end loop

[Bored]

OK, there's a lot I'm gonna mention about your code here, so I'll start off with answering your question. Collision detection in this case is rather simple at the most basic levels. Once the ball has reached the height where it would hit the paddle you simply check if it is within the bounds of the paddle. So if your Y value reaches a certain spot you check if your X value is between left and right values. If so then you change the direction of travel DY.

OK, now for my comments. Firstly please for the sake of all learn to use cls and View.Update. Here's a tutorial of View.Update and View.Set, please see the section on eliminating screen flicker. Next is if you would like change the sign on a variable rather then going variable := variable * -1 you can simply use the *= command which will multiply a variable by a certain number and assign the result to the variable. So you code woul become variable *= -1. Plus brackets are not needed around the -1. You can use this trick asweel for some other operations; +=, -=, /=, div=, mod=, **=, or=, and=, not== (works not how you would expect) and possibly a few other i don't know of. Any ways, your variable right and left can simply be changed to one variable position and replace right with position + 50 and left to position - 50. And finally what is the point of leftr and rightr? The only time you use them is to change there values but you never again use them.

This isn't bad for a starter, just a few things to clean up.

[cpu_hacker4.0]

Here is a really choppy example of a png game I made. It isn't finishe yet, bu the basics are thre. Try using a MathDistance and a MathDistancePointLine for the collision detection with the ball and paddles.

code:

const RADIUS : int := 10 var chars : array char of boolean var paddle1X : int := 5 var paddle1Y : int := maxy div 2 - 50 var paddle2X : int := maxx - 5 var paddle2Y : int := maxy div 2 - 50 var ballX : int := maxx div 2 var ballY : int := maxy div 2 var xInc : int := 1 var yInc : int := 1 var p1score : int := 0 var p2score : int := 0 var p1name : string var p2name : string var reply : string (1) put "Please enter the name for player 1: " .. get p1name put "Please enter the name for player 2: " .. get p2name setscreen ("offscreenonly") function MathDistance (x1, y1, x2, y2 : real) : real     var dx : real := x1 - x2     var dy : real := y1 - y2     result sqrt (dx * dx + dy * dy) end MathDistance function MathDistancePointLine (px, py, x1, y1, x2, y2 : real) : real     var lineSize : real := MathDistance (x1, y1, x2, y2)     if lineSize = 0 then         result MathDistance (px, py, x1, y1)     end if     var u : real := ((px - x1) * (x2 - x1) +         (py - y1) * (y2 - y1)) / (lineSize * lineSize)     if u < 0.0 then         result MathDistance (px, py, x1, y1)     elsif u > 1.0 then         result MathDistance (px, py, x2, y2)     else         var ix : real := x1 + u * (x2 - x1)         var iy : real := y1 + u * (y2 - y1)         result MathDistance (px, py, ix, iy)     end if end MathDistancePointLine loop     loop         cls         ballX += xInc         ballY += yInc         drawfillbox (0, 0, maxx, maxy, yellow)         drawline (paddle1X, paddle1Y, paddle1X, paddle1Y + 100, black)         drawline (paddle2X, paddle2Y, paddle2X, paddle2Y + 100, black)         drawfilloval (ballX, ballY, RADIUS, RADIUS, black)         Input.KeyDown (chars)         if chars ('w') then             paddle1Y += 1         elsif chars ('s') then             paddle1Y -= 1         end if         if chars (KEY_UP_ARROW) then             paddle2Y += 1         elsif chars (KEY_DOWN_ARROW) then             paddle2Y -= 1         end if         if paddle1Y + 100 >= maxy then             paddle1Y -= 1         elsif paddle1Y <= 0 then             paddle1Y += 1         end if         if paddle2Y + 100 >= maxy then             paddle2Y -= 1         elsif paddle2Y <= 0 then             paddle2Y += 1         end if         if ballY + RADIUS >= maxy then             yInc *= -1         elsif ballY - RADIUS <= 0 then             yInc *= -1         end if         if MathDistancePointLine (ballX, ballY, paddle1X, paddle1Y, paddle1X, paddle1Y + 100) <= RADIUS or MathDistancePointLine (ballX, ballY, paddle2X, paddle2Y, paddle2X, paddle2Y + 100) <= RADIUS                 then             xInc *= -1         end if         if ballX - RADIUS <= 0 then             p2score := p2score + 1             cls             ballX := maxx div 2             ballY := maxy div 2             drawfillbox (0, 0, maxx, maxy, yellow)             drawline (paddle1X, paddle1Y, paddle1X, paddle1Y + 100, black)             drawline (paddle2X, paddle2Y, paddle2X, paddle2Y + 100, black)             drawfilloval (ballX, ballY, RADIUS, RADIUS, black)             put p2name, " scored!"             View.Update             delay (1000)         elsif ballX + RADIUS >= maxx then             p1score := p1score + 1             cls             ballX := maxx div 2             ballY := maxy div 2             drawfillbox (0, 0, maxx, maxy, yellow)             drawline (paddle1X, paddle1Y, paddle1X, paddle1Y + 100, black)             drawline (paddle2X, paddle2Y, paddle2X, paddle2Y + 100, black)             drawfilloval (ballX, ballY, RADIUS, RADIUS, black)             put p1name, " scored!"             View.Update             delay (1000)         end if         if p1score = 5 then             put p1name, " wins!"             cls             exit         elsif p2score = 5 then             put p2name, " wins!"             exit         end if         View.Update     end loop     cls     put "Would you like to play again? (y/n)"     View.Update     getch (reply)     if reply = 'n' then         exit     end if end loop

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