Asteroids

[WebKill]

I'm making a game that has a similar feel as asteroids, and I'm a bit stuck.

First off, I want to be able to fire more than one bullet at a time. I was thinking I could use a structure for this, but not eactly sure how to do it.

Also, is there a way to move the form background image? I have a 'space' background tiled to the form and would like it to 'scroll' a little.

Using vb.net 2008

[Jabber]

I created a similar game using vb6. I used Dx7.
The scrolling background is most difficult for me. I can't combine the two.

Here is a method for firing. The shuttle has 24 directions and 24 images in an array.
There may be a much simpler way. But this does work well. Just to give you an idea.

Public Sub ShootFire()        'This is what happens when the player fires
   If (GetTickCount - Shuttle.ShootTime) < 300 Then Exit Sub
      Shuttle.ShootTime = GetTickCount
If Not sFire Then Exit Sub
  Call FireLazer            'DX sound
   
    G = 1
    Do Until Not Mgun(G).act Or G = 20 'find an open slot
        G = G + 1
    Loop
        With Mgun(G)
        .speed = 5
        .act = True:  .X = Shuttle.X:  .Y = Shuttle.Y: .dire = Shuttle.dire
        '.speed = .speed * Shuttle.speed:
         mgNum = mgNum + 1
        .ShootTime = GetTickCount
  
    Select Case Shuttle.dire
        Case 24                         'dire the case #
            .Y = Shuttle.Y + 20:            .X = Shuttle.X + 17
        Case 1
            .Y = Shuttle.Y + 13:            .X = Shuttle.X + 26:
        Case 2
            .Y = Shuttle.Y + 15:           .X = Shuttle.X + 35:
        Case 3
            .Y = Shuttle.Y + 11:            .X = Shuttle.X + 41:
        Case 4
            .Y = Shuttle.Y + 13:            .X = Shuttle.X + 43:
        Case 5
            .Y = Shuttle.Y + 10:            .X = Shuttle.X + 45:
        Case 6
            .Y = Shuttle.Y + 18:            .X = Shuttle.X + 41:
        Case 7
            .Y = Shuttle.Y + 26:            .X = Shuttle.X + 44:
        Case 8
            .Y = Shuttle.Y + 32:            .X = Shuttle.X + 41:
        Case 9
            .Y = Shuttle.Y + 43:            .X = Shuttle.X + 40:
        Case 10
            .Y = Shuttle.Y + 43:            .X = Shuttle.X + 35:
        Case 11
            .Y = Shuttle.Y + 44:            .X = Shuttle.X + 25:
        Case 12
            .Y = Shuttle.Y + 40:            .X = Shuttle.X + 17:
        Case 13
            .Y = Shuttle.Y + 45:            .X = Shuttle.X + 10:
        Case 14
            .Y = Shuttle.Y + 41:            .X = Shuttle.X + 12
        Case 15
            .Y = Shuttle.Y + 44:            .X = Shuttle.X + 12:
        Case 16
            .Y = Shuttle.Y + 33:            .X = Shuttle.X + 15:
        Case 17
            .Y = Shuttle.Y + 26:            .X = Shuttle.X + 15:
        Case 18
            .Y = Shuttle.Y + 19:            .X = Shuttle.X + 20:
        Case 19
            .Y = Shuttle.Y + 12:            .X = Shuttle.X + 17:
        Case 20
            .Y = Shuttle.Y + 14:            .X = Shuttle.X + 15:
        Case 21
            .Y = Shuttle.Y + 11:            .X = Shuttle.X + 12:
        Case 22
            .Y = Shuttle.Y + 11:            .X = Shuttle.X + 7:
         Case 23
            .Y = Shuttle.Y + 12:            .X = Shuttle.X + 9:
       End Select
    End With
    

End Sub

Public Sub MoveMgs()                   'move bullets     ----------
   
    For G = 1 To 20
        With Mgun(G)
            If .act Then
         If btnDown Or goBack Or Shuttle.speed < 2 Then
                 Mgun(G).speed = 1
         Else
         Mgun(G)
     End If
            If .dire = 24 Then                         'dire = case #
           Mgun(G).Y = Mgun(G).Y - 20 * .speed
        ElseIf .dire = 1 Then
            Mgun(G).X = Mgun(G).X + 4 * .speed
            Mgun(G).Y = Mgun(G).Y - 15 * .speed
        ElseIf .dire = 2 Then
            Mgun(G).X = Mgun(G).X + 8 * .speed
            Mgun(G).Y = Mgun(G).Y - 15 * .speed
        ElseIf .dire = 3 Then
            Mgun(G).X = Mgun(G).X + 10 * .speed
            Mgun(G).Y = Mgun(G).Y - 10 * .speed
        ElseIf .dire = 4 Then
            Mgun(G).X = Mgun(G).X + 15 * .speed
            Mgun(G).Y = Mgun(G).Y - 10 * .speed
        ElseIf .dire = 5 Then
            Mgun(G).X = Mgun(G).X + 15 * .speed
            Mgun(G).Y = Mgun(G).Y - 5 * .speed
        ElseIf .dire = 6 Then
            Mgun(G).X = Mgun(G).X + 20 * .speed
        ElseIf .dire = 7 Then
            Mgun(G).X = Mgun(G).X + 15 * .speed
            Mgun(G).Y = Mgun(G).Y + 4 * .speed
        ElseIf .dire = 8 Then
            Mgun(G).X = Mgun(G).X + 15 * .speed
            Mgun(G).Y = Mgun(G).Y + 10 * .speed
        ElseIf .dire = 9 Then
            Mgun(G).X = Mgun(G).X + 10 * .speed
            Mgun(G).Y = Mgun(G).Y + 10 * .speed
        ElseIf .dire = 10 Then
            Mgun(G).X = Mgun(G).X + 9 * .speed
            Mgun(G).Y = Mgun(G).Y + 15 * .speed
         ElseIf .dire = 11 Then
            Mgun(G).X = Mgun(G).X + 4 * .speed
            Mgun(G).Y = Mgun(G).Y + 15 * .speed
         ElseIf .dire = 12 Then
            Mgun(G).Y = Mgun(G).Y + 20 * .speed     'down
        ElseIf .dire = 13 Then
            Mgun(G).X = Mgun(G).X - 4 * .speed
            Mgun(G).Y = Mgun(G).Y + 15 * .speed
        ElseIf .dire = 14 Then
            Mgun(G).X = Mgun(G).X - 10 * .speed
            Mgun(G).Y = Mgun(G).Y + 15 * .speed
        ElseIf .dire = 15 Then
            Mgun(G).X = Mgun(G).X - 10 * .speed
            Mgun(G).Y = Mgun(G).Y + 10 * .speed
        ElseIf .dire = 16 Then
            Mgun(G).X = Mgun(G).X - 15 * .speed
            Mgun(G).Y = Mgun(G).Y + 10 * .speed
        ElseIf .dire = 17 Then
            Mgun(G).X = Mgun(G).X - 15 * .speed
            Mgun(G).Y = Mgun(G).Y + 4 * .speed
        ElseIf .dire = 18 Then
            Mgun(G).X = Mgun(G).X - 20 * .speed       'left
        ElseIf .dire = 19 Then
            Mgun(G).X = Mgun(G).X - 15 * .speed
            Mgun(G).Y = Mgun(G).Y - 5 * .speed
        ElseIf .dire = 20 Then
            Mgun(G).X = Mgun(G).X - 15 * .speed
            Mgun(G).Y = Mgun(G).Y - 10 * .speed
         ElseIf .dire = 21 Then
            Mgun(G).X = Mgun(G).X - 10 * .speed
            Mgun(G).Y = Mgun(G).Y - 10 * .speed
         ElseIf .dire = 22 Then
            Mgun(G).X = Mgun(G).X - 5 * .speed
            Mgun(G).Y = Mgun(G).Y - 10 * .speed
         ElseIf .dire = 23 Then
            Mgun(G).X = Mgun(G).X - 4 * .speed
            Mgun(G).Y = Mgun(G).Y - 15 * .speed
      End If

        If .dire >= 1 And .dire <= 11 Then       '1 thru 11  rightside clock
      If Mgun(G).X >= 1020 Then
        Mgun(G).X = 0:
       End If
       End If
       
      If (GetTickCount - Mgun(G).ShootTime) >= 550 Then      'set stop time
           Mgun(G).act = False
              .X = .X: .Y = .Y: .dire = 0
           End If
        
    If .dire >= 13 And .dire <= 23 Then           '13 thru 23  left side clock
        If Mgun(G).X <= 0 Then
            Mgun(G).X = 1020
          End If
       End If
     
       If .dire >= 7 And .dire <= 17 Then   '17 thru 7  lower clock
      If Mgun(G).Y >= 760 Then
        Mgun(G).Y = 0
       End If
    End If
    
     If .dire >= 20 And .dire <= 24 Or .dire <= 1 Or .dire <= 5 Then   '20 thru 5  upper clock
        If Mgun(G).Y <= 0 Then
            Mgun(G).Y = 760
          End If
       End If
       End If
   End With
    Next G
 End Sub

mGun, shuttle are both UDTs.
Using a game loop you call MoveMgs to move the shots.

I added a space station that the shuttle can dock to recharge and the player must protect the station from asteroids.


.

[Quasar6]

You're right when you say you will need a structure. A class would work as well, but a structure would probably be better for something small like this.

When you build a structure, you need to incorporate whatever information each instance of that stucture will need. So a individual bullet will obviously need a pictureBox (or whatever control you're using to display your bullets), as well as a position and a speed. More advanced structures could also have a damage value, a size value, or whatever else you want.

Since your pictureBox already has an X,Y Location, you won't need to define that. But you will need to define an xSpeed and ySpeed value.

First of all, create your structure:

Public Structure Bullet
 
 
    End Structure

Now initialise the variables you'll need for each bullet:

Dim pictureBox As PictureBox
    Dim xSpeed As Double
    Dim ySpeed As Double

Now add an Update method. You can call this for each Bullet every time the game updates:

Sub UpdateBullet()
        'Move the Bullet
        picBox.Location() = New Point(picBox.Location.X + xSpeed, picBox.Location.Y + ySpeed)
        'Add your collision checking code here
    End Sub

You'll also need a bullet List to keep track of the bullets... something like this:

Dim bulletList As List(Of Bullet)

To use the structure now, simply create a bullet, add it to a bullet list and set it's variables:

Dim x As Bullet
 
x.picBox.Image = myImage 'Preload an image with Dim imageName As Image, then use it
x.xSpeed = 0 'Determine your xSpeed
x.ySpeed = 0 'Determine your ySpeed
 
bulletList.Add(x)

Finally, update all the bullets in your timer_tick method:

Dim y As Bullet
        For Each y In bulletList
            y.UpdateBullet()
        Next

Hope this helps!

Cheers,
Qu.

[WebKill]

Wow, thanks for the awsoem help guys! Quasar6, thats exactly what I was looking for, but I'm having a little trouble still, it's saying "Object reference not set to an instance of an object." at the line with "x.picbox.Image = myshot"

At the top I have:

    myshot = picShot.Image
    Dim shotList As List(Of Shot)

    Public Structure Shot
        Dim X As Double
        Dim Y As Double
        Dim picbox As PictureBox
        Dim speed As Single
        Dim Damage As Single
        Sub UpdateShot()
            picbox.Location() = New Point(picbox.Location.X + X, picbox.Location.Y + Y) 
        End Sub
    End Structure

Then for my mouse click:

                Dim x As New Shot
                x.picbox.Image = myshot 
                x.X = 1
                x.Y = 1
                shotList.Add(x)
                Timer1.Enabled = True

And finally my timer:

        Dim y As Shot
        For Each y In shotList
            y.Updateshot()
        Next

[WebKill]

Ok, I think I got it figured out, but it's still only allowing one shot at a time.

    Public Structure Shot
        Dim X As Double
        Dim Y As Double
        Dim picbox As PictureBox
        Dim speed As Single
        Dim Damage As Single
        Sub UpdateShot()
            'Move the Bullet        
            picbox.Location() = New Point(picbox.Location.X + speed, picbox.Location.Y + speed)
            'Add your collision checking code here
        End Sub
    End Structure

    Public shotList As New List(Of Shot)

Then for mouse click I have this, I want the shot to originate from the ship image, dont care where it goes at this point, just want it to fire multiple shots.

                Dim x As New Shot
                x.picbox = pctShot
                x.picbox.Location() = New Point(mypic.Top + (mypic.Height / 2), mypic.Left + (mypic.Width / 2))
                x.X = mypic.Top + (mypic.Height / 2)
                x.Y = mypic.Left + (mypic.Width / 2)
                x.speed = 1
                x.picbox.Visible = True
                shotList.Add(x)
                Timer1.Enabled = True

And heres the timer:

        Dim y As Shot
        For Each y In shotList
            y.Updateshot()
        Next

[Jabber]

Create an array for new shots and you should be able to have mulitple shots fired.

Dim Shot() as New Shot
Dim A as integer

 For A = 1 to 10
  with Shot(A)
         .pctbox = pctShot
         .x = pic.Top + (mypic.Height / 2)
         .y = mypic.Left + (mypic.Width / 2)
         .speed = 1
                                  'etc.
End With
 Next

[WebKill]

What about the list?

Public shotList As New List(Of Shot)

[Quasar6]

A List is infinitely better than an array, because with an array you're limited to a number of shots equal to the array size. With a list you can keep calling ListName.Add forever and all you'll suffer will be lag when you end up with a googleplex or so shots.

As to your problem... I'm thinking about it... give me a moment, I'll reply properly in a second...

[Quasar6]

OK, I found your problem... rather than copying a bullet picture and putting it in the new Shot Structure, you're actually making an existing pictureBox the bullet. Then whenever you create a bullet all the old bullets still exist, but the picture box representing the bullet moves to only the position of the last bullet you created.

Try replacing this ...

x.picbox = pctShot

... with something like this...

x.picbox = New PictureBox()
x.picbox.Image = pctShot.Image

. As you can see, this will create a new PictureBox rather than just moving the old one.

There is one ather thing I should have mentioned: you need to add the PictureBox to Form1 (Or whatever your form's name is) once it's created. Simply add the following line immediately after x.picbox's attributes are set, but before you add x to the shot list...

Form1.ActiveForm.Controls.Add(x.picbox)

Cheers!

[WebKill]

Doh, that seems obvious, hehe. Only problem is when I do that, the shot never displays, so I see nothing instead of multiples.

[WebKill]

Well, I got the shot to display, but I cant get the thing to move Good greif, lol

Here's my shot structure, the bullet fires at the angle of the ship:

Public Structure Shot
        Dim XPos As Int32
        Dim YPos As Int32
        Dim picbox As PictureBox
        Dim speed As Int32
        Dim distance As Int32
        Dim angle As Int32
        Dim damage As Single
        Sub UpdateShot()
            Dim X, Y As Int32
 
            X = -Math.Sin(angle * Math.PI / 180.0) * 3
            Y = -Math.Cos(angle * Math.PI / 180.0) * 3
 
            XPos = XPos + X
            YPos = YPos + Y
            picbox.Location() = New Point(XPos, YPos)
            'Add your collision checking code here
        End Sub
    End Structure

Here's where the shot is created (mouse click):

x.picbox = New PictureBox
                x.picbox.Image = pctShot.Image
                x.picbox.SizeMode = PictureBoxSizeMode.AutoSize
                'x.picbox.Location = New Point(500, 500)
                x.XPos = myShip.picbox.Location.X + (myShip.picbox.Width / 2)
                x.YPos = myShip.picbox.Location.Y + (myShip.picbox.Height / 2)
                x.speed = 3
                x.distance = 500
                x.picbox.Visible = True
                x.angle = myShip.angle
                Controls.Add(x.picbox)
                shotList.Add(x)

Background worker shot dowork:

For i = 1 To 2
            bwShot.ReportProgress(i)
            If i = 2 Then i = 1
            If bwShot.CancellationPending = True Then
                Exit For
            End If
            System.Threading.Thread.Sleep(30)
        Next

Background worker shot progress changed:

Dim y As Shot
        For Each y In shotList
            y.UpdateShot()
        Next

Now I can tell that it is making the shot because it's displaying it (where the ship is), but it's not moving. Through use of msgbox's I've determined that it's getting inside the updateshot routine, but nothing is changing. the updateshot code is basically the same code for the ships movement, only in this case the angle is constant (set to what angle the ship was at fireing). Any thoughts would be appreciated, I'm probably missing somthign obvious.

[WebKill]

Ok, got it down to this:

XPos = XPos + X
YPos = YPos + Y

For some reason, those variables wont add together, they all have values, but they wont add together for some reason, any thoughts?

[Quasar6]

Yep... I think it's a rounding problem, because you're defining X and Y as Integers. This means that if your maths eqation returns less than 0.5, they'll return as 0.

You are going to need to place the final .Location values as integers, but until you do that try to set all your number variables (X,Y, XPos, YPos) as Single (and only convert to Int at the last moment).
Here:

    Public Structure Shot
        Dim XPos As Single
        Dim YPos As Single
        Dim picbox As PictureBox
        Dim speed As Int32
        Dim distance As Int32
        Dim angle As Int32
        Dim damage As Single
        Sub UpdateShot()
            Dim X, Y As Single
            X = -Math.Sin(angle * Math.PI / 180.0) * 3
            Y = -Math.Cos(angle * Math.PI / 180.0) * 3
            XPos = XPos + X
            YPos = YPos + Y
            picbox.Location() = New Point(CInt(XPos), CInt(YPos))
            'Add your collision checking code here     
        End Sub
    End Structure

[WebKill]

tried that, didn't work.

I can see values for each of them, for instance

525 = 525 - 3

and guess what it returns? 525

[Quasar6]

*confused frown...*

That makes no sense whatsoever. Try this, and let me know what it returns:
Sub UpdateShot()

Dim X, Y As Single
            X = -Math.Sin(angle * Math.PI / 180.0) * 3
            Y = -Math.Cos(angle * Math.PI / 180.0) * 3
msgBox(XPos+" += "X)
            XPos += X
            YPos += Y
msgBox(XPos)
            picbox.Location() = New Point(CInt(XPos), CInt(YPos))
            'Add your collision checking code here     
        End Sub

If XPos is the same before and after, something is seriously messed up.

[WebKill]

I figured it out I needed to set xpos and ypos and shared variables. it's moving now, but theres only 1 at a time, grumble, still cant get that part workign, lol

[Quasar6]

Sharing XPos and YPos shouldn't do anything other than make the same XPos and YPos apply to all instances of Shot (with obvious consequences).

I'm confused as to the other problem though... can't see whats going wrong. I'll keep thinking on it..

[WebKill]

Hmm, well sharing it made it work, but when I fire more than 1, it seems to reset and it looks like 2 go at teh same time, so maybe thats the sharing problem? also, I want to make sure it gets destroyed when it's life is up, so I did this:

If life >= distance Then
                shotList.RemoveAt(shotIndex)
            End If

but it throws this error when it gets to it: "Exception has been thrown by the target of an invocation."
Seems like a pretty general error?

[WebKill]

Yeha I just tried taking the shared out and just dim the vars and i have landmines instead of shots again :\ This makes no sense at all because it works just fine for the ship movment, but for some reason Xpos and Ypos do not want to change values.

[WebKill]

Ok, it apears that the variables are resetting each time, they are getting set, but each time updateshot is called it gets reset. Here's my updated code:

List declared at the top to hold all the shots, plus index so I can destroy a shot

Public shotList As New List(Of Shot)
Public shotIndex As Int32

Heres the Structure:

Public Structure Shot
        Dim XPos As Single
        Dim YPos As Single
        Dim anglex As Single
        Dim angley As Single
        Dim picbox As PictureBox
        Dim speed As Int32
        Dim distance As Int32
        Dim damage As Int32
        Dim life As Int32
        Dim turrent As Boolean
        Sub UpdateShot()
            XPos = XPos + anglex
            YPos = YPos + angley
 
            picbox.Location() = New Point(CInt(XPos), CInt(YPos))
 
            life = life + 1
 
            'Add your collision checking code here
        End Sub
    End Structure

Here’s the creation at mouse click:

x.picbox = New PictureBox
                x.picbox.Image = pctShot.Image
                x.picbox.SizeMode = PictureBoxSizeMode.AutoSize
                x.picbox.Location = New Point(myShip.picbox.Location.X + (myShip.picbox.Width / 2), myShip.picbox.Location.Y + (myShip.picbox.Height / 2))
                x.XPos = myShip.picbox.Location.X + (myShip.picbox.Width / 2)
                x.YPos = myShip.picbox.Location.Y + (myShip.picbox.Height / 2)
                x.anglex = -Math.Sin(myShip.angle * Math.PI / 180.0) * 3
                x.angley = -Math.Cos(myShip.angle * Math.PI / 180.0) * 3
                x.speed = 3
                x.distance = 200
                x.picbox.Visible = True
                Controls.Add(x.picbox)
                shotList.Add(x)

Update shot is called by a background worker (a separate thread) that is constantly checking for shots, looping through the list and updating each one.

Dim y As Shot
        For Each y In shotList
            If y.life >= y.distance Then
                y.life = 0
                shotList.RemoveAt(shotList.IndexOf(y))
            End If
            y.UpdateShot()
            Label4.Text = y.life
        Next

[Quasar6]

I honestly can't work out what's going on.

I have one little thought... try changing UpdateShot to:

            Me.XPos = Me.XPos + Me.anglex
            Me.YPos = Me.YPos + Me.angley

            Me.picbox.Location() = New Point(CInt(Me.XPos), CInt(Me.YPos))

            Me.life = Me.life + 1

I doubt it will make any difference, but it might work... If it doesn't, try putting it outside of your structure (in the namespace, changing it to this:

        Sub UpdateShot(this As Shot)
            this.XPos = this.XPos + this.anglex
            this.YPos = this.YPos + this.angley

            this.picbox.Location() = New Point(CInt(this.XPos), CInt(this.YPos))
             this.life = this.life + 1
             'Add your collision checking code here
        End Sub

, and calling it like this:

UpdateShot(y)

I'm not sure whether any of this will work, but it's the only thing I can think of to try.

[WebKill]

Figured it out, changed it to a class instead of a structure. With a structure it was updating a copy of it, thats why it wouldn't stay. With a class, it accesses the same point in memory. Wow that one baffled me for a while, lol.

[Quasar6]

Yay! Remember to mark your thread resolved.