A confusing question

I have a question that I was wondering if someone could at least make a guess as to what the problem is with my program.

I'm designing an RPG with the bit blit function. The combat requires about 50 frames of animation (which means about 100 sprites and masks), between your character and the enemey.

I have all the masks and sprites in their own picture box on separate forms and use timers to change which frame should be displayed then another timer that redraws the combat screen and sprites every 10 miliseconds weather they have been changed or not by looking at a case statement then drawing the correct mask and sprite.

I also initialize all the drawing fuctions before the combat begins by drawing every single one onto the combat window then erasing them before the user can see it. This increases the performance, otherwise the first time you do a move it will be sluggish.

Now finally to the problem. I've found that one random frame always seems to get screwed up displaying a large black area, and will remain screwed up unless you turn off the computer entirely then turn it back on and try again. But this only happens sometimes other times not at all.

Can anyone guess what that problem might be what is going on?

I assume the hdc property or picture itself is somehow getting screwed up during the initilization process. To combat it I now replace every picture in the picture boxes with one from a resource file after the initalization takes place and I have never had that problem since. But I'd really like to know what is causing it, because I really don't understand.

I'll take a guess. Sounds like a resource problem. On the start menu there is the Resource Meter (Start/Accessories/System Tools/Resource Meter) Run it before you run your program and then check it when you start to have problems. If resources get too low all kinds of screwy things can start to happen.

Needless to say 50 pictureboxes are using up a lot of resources, and when you have a lot of BitBlts going on continuosly Windows can get backed up. You can try peppering your code with DoEvents and see if that helps, especially in loops.

Another thing you may want to consider is combining a lot of the pictures into one larger picture and store it in one picturebox or maybe 10 or 15 pictureboxes. Just cut down the number as much as you can. Then you can BitBlt sections of it as needed.

Just a thought.

Greg

You shouldnt be blitting from pictureboxes at all actually.
Create device contexts.

VB Code:

Option Explicit
 
Private Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hDc As Long) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hDc As Long) As Long
Private Declare Function LoadImage Lib "user32" Alias "LoadImageA" (ByVal hInst As Long, ByVal lpsz As String, ByVal un1 As Long, ByVal n1 As Long, ByVal n2 As Long, ByVal un2 As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Private Declare Function SelectObject Lib "gdi32" (ByVal hDc As Long, ByVal hObject As Long) As Long
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
 
Public Function GenerateDC(FileName As String) As Long
    Dim DC As Long, picTemp As IPictureDisp
    DC = CreateCompatibleDC(0)
    If DC < 1 Then
        Exit Function
    End If
    Set picTemp = LoadPicture(FileName)
    SelectObject DC, picTemp
    DeleteObject picTemp
    Set picTemp = Nothing
    GenerateDC = DC
End Function
 
Private Sub Form_Load()
    Dim myDc As Long
    myDc = GenerateDC("c:\jamie\jamie.bmp")
    With Picture1
        .AutoRedraw = True
        BitBlt .hDc, 0, 0, .Width, .Height, myDc, 0, 0, vbSrcCopy
    End With
End Sub

The way I always did it was to have one picturebox for each sprite. There's an excellent tutorial on that at Fox's web site - http://orion.spaceports.com/~mccloud/

Thanks plenderj but how do you suggest I implement that code so ALL the sprites are in memory at once. If I use that code you posted every time I bit blit something the performance is really going to go down. I know with Direct X (which I'm not using in this project) you can load all the sprites into an array. Can I do that with that code without loseing the hDC property? The reason I have picture boxes right now is because its proved to be the fastest performance, but I'm sure an array would be better.

actually at a second look that might work. I tryed to implement something similar once and it was totally not working, but let me give that a try thanks.

Well, in the site I gave there's an article on blting lots of frames from a single DC, and another one on loading an offscreen DC without wasting resources every time you blt...

Zaknafein,

What you do is as follows.
You show a loading screen for example.
And what you do is create device contexts for all the sprites.
You can have an array of Longs, or just lots of variable names.
Anyway you create lots. And once you've created them, thats that.
Eg:

VB Code:

shipUp = GenerateDC("c:\jamie\up.bmp")
shipDown = GenerateDC("c:\jamie\down.bmp")
shipLeft = GenerateDC("c:\jamie\left.bmp")
shipRight = GenerateDC("c:\jamie\right.bmp")

Once those device contexts have been created, then each time you want to draw a picture you'd do :

VB Code:

Select Case True
    Case goUp:
        BitBlt destPBox.hDc, 0, 0, destPBox.Width, destPBox.Height, shipUp, 0, 0, vbSrcCopy
    Case goDown:
        BitBlt destPBox.hDc, 0, 0, destPBox.Width, destPBox.Height, shipDown, 0, 0, vbSrcCopy
    Case goLeft:
        BitBlt destPBox.hDc, 0, 0, destPBox.Width, destPBox.Height, shipLeft, 0, 0, vbSrcCopy
    Case goRight:
        BitBlt destPBox.hDc, 0, 0, destPBox.Width, destPBox.Height, shipRight, 0, 0, vbSrcCopy
End Select

well if i was you, i would scrap bitblt and use DirectX. once you get past creating surfaces and all the start-up code, its alot easier than Bitblt + you don't have to make masks!

and if you want i will upload my graphics class which does alot of the work for you (although it was done with sports games inmide, i am sure it wouldnt take that much work to bring it up to RPG standards....)

JSG

Thank you for all the replys. This is very helpful. Yes JSG I would like to see your direct X graphics class if you don't mind.