moving the ball in PONG

[kylekocak]

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick, MyBase.Move
        Dim movepix As Integer
        movepix = 5
        Ball = Me.CreateGraphics
        Ball.Clear(Color.Gray)
 
        If y = 230 Then
            movepix = (movepix * -1)
 
        End If
        If y = 0 Then
            movepix = (movepix * -1)
 
        End If
        If x = 230 Then
            movepix = (movepix * -1)
 
        End If
        If x = 0 Then
            movepix = (movepix * -1)
 
        Else
            x += movepix
            y += movepix
        End If
 
 
        Ball.FillEllipse(Brushes.Yellow, x, y, 20, 20)
    End Sub

this is what i came up with for moving the ball in a pong game i am creating.....all the ball does is travel at a diagonal until it gets stuck in the lower-right corner.....i can't get the balll to richochet or move around the dimensions of the window.....also, i cant find a good was of clear the ball graphic without changing the backfround color.

[fartman_900]

The problem that you are having is that you are using the same variable for moving the ball in the x and y directions.

What you should do is have 2 variables for the balls speed, like xSpeed and ySpeed and set them to whatever. Then when the ball's x position is less than 0, make xSpeed = -xSpeed, when the x position+width of ball is greater than the right side of the screen, again make xSpeed = -xSpeed. Similarly for the y bounds and ySpeed. Then in the timer, do the bound checks then at the end do: ball.x += xSpeed and ball.y +=ySpeed.

Just taking your code and changing it:

      Dim xSpeed As Integer       'set the values for these
      Dim ySpeed As Integer
 
      Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick, MyBase.Move
              Ball = Me.CreateGraphics
              Ball.Clear(Color.Gray)

              If (y + Ball.height)>= 230 Then
                  ySpeed = -ySpeed
              End If
              If y <= 0 Then
                  ySpeed = -ySpeed
              End If
              If (x + Ball.width)>= 230 Then
                  xSpeed = -xSpeed
              End If
              If x <= 0 Then
                  xSpeed = -xSpeed
              End If
              x += xSpeed
              y += ySpeed
      
              Ball.FillEllipse(Brushes.Yellow, x, y, 20, 20)
          End Sub

Those conditions may have to change for the Y, I forget if VB starts counting the Y coordinate from the top or the bottom.

[kylekocak]

that's kinda of a general problem i have been running in to....... the .height() and .width() are not members of the System.Drawing.Graphics class.....

[fartman_900]

Ok, well if they aren't members of that class, just use constants instead of calling those functions/methods. I see that in the Ball.FillEllipse line, that you are using 20 for the height and width, so just change the conditions to be x + 20 and y + 20.

EDIT
I just looked as MSDN site and that is really odd, and kind of stupid, that the class doesn't have width and height functions OR member variables. lol

[singularis]

There is nothing strange about the graphics class having to member varibles. This is because the graphics class does not mean a 'graphic' as such but the graphics class is an interface to draw shapes.

[kylekocak]

well, what is the best way to manipulate their location...re-draw them every Timer1_Tick()?

[singularis]

That or use a managed game loop. It is a lot simpler than it sounds. Just make a while loop and put the DoEvents in it. Usually when you start a loop, windows forgets to breathe until it finishes and your computer crashes. DoEvents stops this from happening and tells windows to breathe.

Note that this code is classic VB code but the principles should remain.

Dim bLoop as Boolean
bLoop = true
While(bLoop)
'<- Put game code here
System.DoEvents
wend

Avoid using timers as much as you can !

[fartman_900]

There is nothing strange about the graphics class having to member varibles. This is because the graphics class does not mean a 'graphic' as such but the graphics class is an interface to draw shapes.

Oh, ok. I guess I didn't read the document like I should have lol, thanks.

[vbNeo]

You might also want to look into 2D vectors if you plan on doing more 2D programming(or 3D for that matter) - they help a lot when calculating and understanding objects in a coordinate system.

[kylekocak]

Dim movepix As Integer
        Dim negmovepix As Integer
        Dim go As Boolean
        go = False
        movepix = 5
        negmovepix = -5
        Ball = Me.CreateGraphics
        Ball.Clear(Me.BackColor)
        While go
            x += 5
            y += 5
            Ball.FillEllipse(Brushes.Yellow, x, y, 20, 20)
            Application.DoEvents()
        End While

I put that in, but when i run it, the program just flashed a ball and bar and then disappears, how do i get the program to move my ball around and my bar to NOT disappear. also i want to be able to run my keypress...

Private Sub Form1_KeyPress(ByVal sender As Object, ByVal e As KeyPressEventArgs) Handles Me.KeyPress
        Bar = Me.CreateGraphics
        Select Case e.KeyChar
            Case ","c
                Ball.Clear(Me.BackColor)
                Bar.FillRectangle(Brushes.Black, (x1 - 10), 295, 80, 15)
                x1 = x1 - 10
            Case "<"c
                Ball.Clear(Me.BackColor)
                Bar.FillRectangle(Brushes.Black, (x1 - 10), 295, 80, 15)
                x1 = x1 - 10
            Case "."c
                Ball.Clear(Me.BackColor)
                Bar.FillRectangle(Brushes.Black, (x1 - 10), 295, 80, 15)
                x1 = x1 + 10
            Case ">"c
                Ball.Clear(Me.BackColor)
                Bar.FillRectangle(Brushes.Black, (x1 - 10), 295, 80, 15)
                x1 = x1 + 10
            Case "s"c
 
                Timer1.Start()
                Ball.FillEllipse(Brushes.Yellow, x, y, 20, 20)
                Bar.FillRectangle(Brushes.Black, x1, 295, 80, 15)
        End Select
    End Sub

[fartman_900]

The first thing that is wrong is that you set go to false, when it should be true. So the loop is executing once then ending. Also, inside the while loop you need to put the collision statements (or a method call to check for collisions). As for the key press, I'm not entirely sure (I don't code in VB at all) but I thought that the KeyPress method gets called automatically when a key is pressed so it might be fine. Just another thing about the case statements, all of them move the bar down, just change two of them to + 10 instead of - 10.

[singularis]

@kylekocak: Read Fartman's post. If you want nice smooth keyboard input then I suggest trying a little trick:

You create a varible remembering the velocity of the paddle
e.g. Dim Vel as Long

Then in keypress event set the velocity to 1 if they press right and -1 if they press left.

Then in the code in the loop you tell the ball to move depending on its velocity
e.g. x1 = x1 + Vel

That way the paddle will move smoothly

[kylekocak]

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick, MyBase.Move
        Ball = Me.CreateGraphics
        Ball.Clear(Me.BackColor)
        If y >= 230 Then
            Do
                y -= 5
                Ball.FillEllipse(Brushes.Yellow, x, y, 20, 20)
                Application.DoEvents()
            Loop Until y <= 0
        Else
            x += 5
            y += 5
            Ball.FillEllipse(Brushes.Yellow, x + 5, y + 5, 20, 20)
        End If
        If x >= 230 Then
            Do
                x -= 5
                Ball.FillEllipse(Brushes.Yellow, x, y, 20, 20)
                Application.DoEvents()
            Loop Until x <= 0
        Else
            x += 5
            y += 5
            Ball.FillEllipse(Brushes.Yellow, x, y, 20, 20)
        End If
    End Sub[HIGHLIGHT=vb]

[/HIGHLIGHT]

This code gets the ball to move around the screen, problem is once it hits the 230 for the x and y coordinates, it "transports" to the x or y =0 respectively.....and yes, it is because it is in a Do loop, no need to point that out....i thought the application.DoEvents would have taken care of that.....how do i get the ball to SLOWLY move?

[singularis]

Lower the value from 5 to 0.1 !