Stumped, PLEASE HELP!

K I'm rather new to VB game programming. Not to game programming in general, but in VB. So this is all wierd to me.

Here's the problem:
I have 2 main picture objects, picBackBuffer and picFrontBuffer. Then there is Picture1, with is simply gonna be bitblitted to the main pictures. The process I have come up with, whether it is efficient or not it is good enough for the class I am taking, is simple: BitBlt everything to the picBackBuffer, then bitblt the backbuffer to the frontbuffer. VERY EASY STUFF. The problem is in the loops, I try using a timer to do this but it's being a 8!7<|-|. I have the bitbltting in a "DrawEverything" function, and I check for arrow keys being down (or not down) through 2 other functions. The timer is enabled at start, and its interval is 1. ITS SOO SIMPLE BUT I DON'T SEE WHY IT ISNT WORKING!! Here is the bulk of the problem:

VB Code:

Private Sub form_load()
  ShipX = picBackBuffer.ScaleWidth / 2 - Picture1.ScaleWidth / 2
  ShipY = picBackBuffer.ScaleHeight - 24
End Sub
Private Sub Timer1_Timer()
  Timer = Timer + 1
  If Timer = 6 Then
    Call GetKeyDown(keyRight, ShipSpeedX, 2)
    Call GetKeyDown(keyLeft, ShipSpeedX, -2)
    Call GetKeyDown(keyDown, ShipSpeedY, 2)
    Call GetKeyDown(keyUp, ShipSpeedY, -2)
    Call GetNoKeyDown
    Call DrawEverything
  End If
  If Timer > 6 Then Timer = 0
  Label1.Caption = Timer
End Sub
 
Private Function DrawEverything()
  BitBlt picBackBuffer.hDC, ShipX + ShipSpeedX, ShipY + ShipSpeedY, _
    Picture1.ScaleWidth, Picture1.ScaleHeight, Picture1.hDC, 0, 0, vbSrcCopy
  BitBlt picFrontBuffer.hDC, 0, 0, picBackBuffer.ScaleWidth, _
    picBackBuffer.ScaleHeight, picBackBuffer.hDC, 0, 0, vbSrcCopy
End Function
Private Function GetKeyDown(Key, Action, Amount)
  If GetAsyncKeyState(Key) = 1 Then
    Action = Amount
  End If
End Function
Private Function GetNoKeyDown()
  If GetAsyncKeyState(keyRight) = 0 And GetAsyncKeyState(keyLeft) = 0 Then
    ShipSpeedX = 0
  End If
  If GetAsyncKeyState(keyUp) = 0 And GetAsyncKeyState(keyDown) = 0 Then
    ShipSpeedY = 0
  End If
End Function

I know there is nothing wrong with the bitblt stuf, because it works when I put it in the form load event. The real reason I made this is ust to test out moving things around with that API function GetAsyncKeyState.

I could REALLY use someones help here, it seems like it is a very simple problem to fix, some little thing I don't know about VB that I'm doing wrong or something. Thanx!

(PS hehe I don't think I ever actually gave the PROBLEM -- Nothing is drawn, or bitbltted, when I use the timer. It works when I put it in Form_load, but then it only draws once, defeating the purpose of the timer.)

In a rush so not had chance to look properly.

Firstly, timer delays are in milliseconds, so a delay of 1 is largely pointless.

For more precise timing use the GetTickCount API call. Look it up.

Make sure the autoredraw properties of the things you're drawing on are set correctly and that you refresh them after drawing ops.

Hope that helps.... :)

Test if the timer handler is caled at all: output a debug message or pop up a message box (be warned: the box will come again and again)

Well, the stuf in the timer happens every 6 milliseconds, take a look at it again. But it's not specific time measurement I'm after, It's more of a main loop, which VB doesn't seem to have (or need, for what VB's purposes were for). So I thought a timer would work as a main loop. I only have a couple weeks to work on this game, everybody else in my class are doing simple things like card games, and I'm too advanced to do a card game. Obviousely I'm not far into VB game development, but I've programmed games in other langs before. So tell me, is using a timer a bad way to create a main loop?

A timer is a good way to do a loop but always remember that 1000 delay = 1 second.

Timers are evil. Write your own loop, as shown in all games which need to react fast. Also, don't name your variable 'Timer', as it's already in use by VB and will certainly mess up your logic...

Ugh. So how can I write my own loop, just stick it in the form_load event? I've tried doing that a coulpe times and all it does is crash the program. Ack, once I get around this stupid VB stuf I'll be happy. I don't like the way everything in the code for a form has to be under a "Private" or "Option Explicit". What the hell does Option Explicit MEAN?? AAAAHHHH!!! So anyways, yeah how do I make my own loop?

Option Explicit: this makes the VB compiler check that you have declared every variable you use. As annoying as it may look, it's actually a great option which should be on by default. It helps you to think about the variable types you'll need, and more importantly; it helps debugging in case you have mistyped a variable name...


As for the loop:

First call Form.Show(), this'll make sure the form is actually visible before you enter the loop. Next, make sure you call DoEvents at least once in the loop, this gives Windows a chance to perform various tasks, the most important one being updating your window and make it respond to user actions...

Make sure you also use something like a global bRunning Boolean variable to make a loop look like 'while bRunning' so you can set it to False when you need the game to stop...

Quote:

---

Next, make sure you call DoEvents at least once in the loop, this gives Windows a chance to perform various tasks, the most important one being updating your window and make it respond to user actions...

---

K, I don't know what DoEvents is. Call me whatever names you like, I'm used to other basic langs, and haven't seen/used that before. So help me out here, what do you mean?

Quote:

---

Make sure you also use something like a global bRunning Boolean variable to make a loop look like 'while bRunning' so you can set it to False when you need the game to stop...

---

Could I do something like

VB Code:

while GetAsyncKeyState(vbKeyEscape) = 0
  blah
wend

?

Yes, you can do that too...


DoEvents is a Visual Basic call which lets Windows process any messages it has in your application's queue, messages like keyboard and mouse actions or the repainting of your window (which offcourse is very important, otherwise it looks like your application has crashed :))

Answers to the last reply I just made are still needed, I just tried making a loop again, here's what I made:

VB Code:

Private Sub form_load()
  ShipX = picBackBuffer.ScaleWidth / 2 - Picture1.ScaleWidth / 2
  ShipY = picBackBuffer.ScaleHeight - 24
  Form1.Show
  While GetAsyncKeyState(vbKeyEscape) = 0
    Call GetKeyDown(keyRight, ShipSpeedX, 2)
    Call GetKeyDown(keyLeft, ShipSpeedX, -2)
    Call GetKeyDown(keyDown, ShipSpeedY, 2)
    Call GetKeyDown(keyUp, ShipSpeedY, -2)
    Call GetNoKeyDown
    Call DrawEverything
  Wend
  End
End Sub

The only thing that works about it is that it will quit after a few seconds of holding the escape key.. It doesn't display the form fully, and nothing is functional except the escape key. Pretty much, this freezes my computer until i hold down the escape key for a few seconds. I'm guessing what you mentioned before will help, but I still dunno what that is!

VB Code:

Call DrawEverything
    DoEvents
  Wend

...try that

Oh hehe, I just replied right after you did.. So what do I do, put DoEvents at the end of that loop?

haha JEEZ, did it again! Is this your job or something? Thnx!

Okay well now it refreshes the window, and the bitblitting works again!! woo! but heres another problem: this loop is making my computer CRAWL. its a 1ghz, so speed isn't the issue. The ship won't move, and it takes about 5 seconds of holding down the Esc key for it to Esc heh. Any clue?

You have found the reason why VB is not really suited to graphically intensive applications, except for apps using 3rd party controls like flash etc. VB is as easy as it is because a lot of automation is going on in the background. I started C++ almost a year ago (after VB'ing for 2 years ) and I am still amazed at the differences in speed whenever you need to do mathematically intensive operations (which is what lots of graphics amount to).

I did not look at your code in detail, but it seems you want to do intro animation?

Why not whip up a little bit o' Shockwave and play that for an Intro? I myself made Little Shckwave players when I started with VB, and they were OK on resources.

BS. Sure, I've stopped using VB too because of it's limitations, moved on to Delphi, which is equal to C in terms of speed (btw, no, I will not argue about that again ;)). But that doesn't mean that you can blame this entirely on VB, as I've been programming a lot of games in VB, both with and without DirectX, they always ran pretty smooth...

The problems is definitely in your code. Try adding some code which measures the time it takes for each part to finish (use GetTickCount, or QueryPerformanceCounter if you need really accurate measurement, and write the results to some log or screen. This extra handling does slow down your program, but not the parts it's measuring), then try to figure out why it's slow or post that code here...



Btw, I programmed VB on a P133 and got 30 FPS easily, so it shouldn't be too hard on a 1 Ghz :)

no, no, not an intro animation. I'm just trying to see if I can get a ship to move around the screen. A 32x24 bmp in one picture object, a BackBuffer picture object where everything is drawn to in the background, then when that is finished it will all be drawn to the FrontBuffer picture object. It's just a test, really, because I've just started out with graphics in VB, and it's much different for gamin than other langs. I will go post this file on my site, it's REALLY small and has very little code, so I would appreciate it if someone would take a look. This is for a school project that I really need to get going on. BTW, it's not really mathematically intensive at all. You'll see :P

K, I just uploaded it, its all of ONE K heheh. It's here:

http://www.angelfire.com/rpg/quadama...s/ShipTest.zip

You have to 'copy shortcut' that and paste it in your browser, since Angelfire doesn't support direct file linking. The problems are descibed in the file. I hope someone knows what's wrong!

VB is pretty slow, but something simple like a ship moving around is not all that processor intensive. BitBlt will perform exactly the same in both VB and C/C++/Delphi, because it was written in C (or assembly) in the first place. The place VB slows down in is the logic itself. In this case, there is nearly 0 logic going on, so the difference between VB and the other languages is negligable.

On the other hand, when you start to really need every clock cycle, VB is a death wish.

Z.

I understand the limitations of VB and that it isn't the preferred language to develop games in. But I'm doing this for a school project, and it has to be done in VB 6.0. Also, we're only talking about a vertical scrolling space invaders style game here, probably be bitbltting like no more than 30 or 40 things onto the screen, and will not have any intensive math. So speed is not the issue here, the issue is making this simple little thing work! It won't, and by now I thought I would have the little spaceship moving around the screen, with at least one enemy done, and some shooting.. but I don't even have the ship's movement done! HELP!!

i dont know that i can be of much help coding wise, but www.vbapi.com has a very in depth explanation of how to use these well.

BitBlt probably has a front-end in C (parameter validation and such) and then does it's own display driver calls, which will be partly C and partly asm.

Well, I'll put the code here where I'm 99% sure is the problem. It's the main loop I put in at the end of the form_load. The part that doesn't work is actually moving the ship around when you hold the arrow keys, so something could be wrong with the GetKeyDown function or GetNoKeyDown function. Those simply detect if an arrow key is down or not down with the GetAsyncKeyState API function. Here's the form_load and the GetKeyDown and GetNoKeyDown functions:

VB Code:

Private Sub form_load()
  'First we position the ship at the bottom midlle of the screen
  ShipX = picBackBuffer.ScaleWidth / 2 - Picture1.ScaleWidth / 2
  ShipY = picBackBuffer.ScaleHeight - 24
  'And I'm guessing here's where I screw up. I guess I'm not
  'handling this loop correctly or something. The program pretty
  'much freezes, but if you hold escape for about 5 seconds
  '(on my computer) it will end the program.
  Form1.Show
  While GetAsyncKeyState(vbKeyEscape) = 0
    Call GetKeyDown(keyRight, ShipSpeedX, 2)
    Call GetKeyDown(keyLeft, ShipSpeedX, -2)
    Call GetKeyDown(keyDown, ShipSpeedY, 2)
    Call GetKeyDown(keyUp, ShipSpeedY, -2)
    Call GetNoKeyDown
    Call DrawEverything
    DoEvents
  Wend
  End
End Sub
 
Private Function GetKeyDown(Key, Action, Amount)
  'This function retrieves an arrow key down, then sets the ship's
  'speed accordingly.
  If GetAsyncKeyState(Key) = 1 Then
    Action = Amount
  End If
End Function
Private Function GetNoKeyDown()
  'This determines if none of the arrow keys are down
  If GetAsyncKeyState(keyRight) = 0 And GetAsyncKeyState(keyLeft) = 0 Then
    ShipSpeedX = 0
  End If
  If GetAsyncKeyState(keyUp) = 0 And GetAsyncKeyState(keyDown) = 0 Then
    ShipSpeedY = 0
  End If
End Function

I know there is nothing wrong with the DrawEverything function, so don't worry about that, and I know I have the API functions declared correctly, so don't worry about that. Again, the file is in a post a few posts up, if this code isn't enough to determine the problem. I would really appreciate someone looking at this, because I have no clue what's wrong and this thing is due friday!

I GOT IT!! I got rid of the loop, for some reason it was running EXTREMELY SLOW on my computer (1ghz, 256mb ram) and it ran faster on the school's imacs with virtual pc.. So I used a timer again, and was back to the same original problem. It wouldn't bitblt! So I checked everything 10x over and finally came to an epiphany. Here's what I had before in the DrawEverything function:

VB Code:

Private Function DrawEverything()
  BitBlt picBackBuffer.hDC, ShipX + ShipSpeedX, ShipY + ShipSpeedY, _
    Picture1.ScaleWidth, Picture1.ScaleHeight, Picture1.hDC, 0, 0, vbSrcCopy
  BitBlt picFrontBuffer.hDC, 0, 0, picBackBuffer.ScaleWidth, _
    picBackBuffer.ScaleHeight, picBackBuffer.hDC, 0, 0, vbSrcCopy
End Function

Here's the new one, with a couple extremely obvious things that make it work:

VB Code:

Private Function DrawEverything()
  picBackBuffer.Cls
  BitBlt picBackBuffer.hDC, ShipX + ShipSpeedX, ShipY + ShipSpeedY, _
    Picture1.ScaleWidth, Picture1.ScaleHeight, Picture1.hDC, 0, 0, vbSrcCopy
  BitBlt picFrontBuffer.hDC, 0, 0, picBackBuffer.ScaleWidth, _
    picBackBuffer.ScaleHeight, picBackBuffer.hDC, 0, 0, vbSrcCopy
  picBackBuffer.Refresh
  picFrontBuffer.Refresh
End Function

Just clear the backbuffer and refresh the pictures!! IT WORKS!! :D