Loop, DoEvents, etc....

[git]

Hiyas,

I've finished making the core blit engine of my isometric game. I just fixed a problem involving blitting only visible tiles (my game uses multiple height levels), and the next problem to solve is to do with the game's blit/loop architechture.

Here's the basic architechture so far:

Private Sub Form_Load()
    'Load/do stuff
    Mouse
End Sub

Private Sub Mouse()
    'Declarations, etc.
    Do
        'Clear the screen
        GameForm.Cls
        'Get mouse pos.
        GetCursorPos CursorPos
        CursorPos.X = CursorPos.X - (Me.Left / Screen.TwipsPerPixelX)
        CursorPos.Y = CursorPos.Y - (Me.Top / Screen.TwipsPerPixelY)
        'Scrolling if necessary
        If GetActiveWindow = GameForm.hWnd Then
            If CursorPos.X > -1 And CursorPos.X < 50 Then
                Tactical.YOffset = Tactical.YOffset - 1
            ElseIf CursorPos.X > (GameForm.Width / 15) - 50 And CursorPos.X < (GameForm.Width / 15) + 1 Then
                Tactical.YOffset = Tactical.YOffset + 1
            End If
            If CursorPos.Y > -1 And CursorPos.Y < 50 Then
                Tactical.XOffset = Tactical.XOffset - 1
            ElseIf CursorPos.Y > (GameForm.Height / 15) - 50 And CursorPos.Y < (GameForm.Height / 15) + 1 Then
                Tactical.XOffset = Tactical.XOffset + 1
            End If
        End If
        'Blit sequence
        For ZArray = 1 To Tactical.ZLevel
            BlitStatus = 0
            Ver = -1
            Step = 0
            Do Until Ver = ScreenVer
                Hor = -1
                If Step = 0 Then
                    Step = 1
                ElseIf Step = 1 Then
                    Step = 0
                    Ver = Ver + 1
                End If
                Do Until Hor = ScreenHor
                    Hor = Hor + 1
                    HorBlit = (Hor - (Step / 2)) * 40
                    VerBlit = ((Ver + (Step / 2)) * 20) - 38
                    MapXCoOrd = Tactical.XOffset + Tactical.YOffset - (Tactical.YMapSize / 2) + Hor + Ver
                    MapYCoOrd = Tactical.XOffset - Tactical.YOffset + (Tactical.YMapSize / 2) - Hor + Ver + Step
                    If MapXCoOrd + ((ZArray - 1) * 2) > 0 And MapYCoOrd + ((ZArray - 1) * 2) > 0 And MapXCoOrd + ((ZArray - 1) * 2) < Tactical.XMapSize + 1 And MapYCoOrd + ((ZArray - 1) * 2) < Tactical.YMapSize + 1 Then
                        If CurrentLevelData.VisibleCheckArray(MapXCoOrd + ((ZArray - 1) * 2), MapYCoOrd + ((ZArray - 1) * 2), ZArray) = 1 And Not Map(MapXCoOrd + ((ZArray - 1) * 2), MapYCoOrd + ((ZArray - 1) * 2), ZArray).Tile = 0 Then
                            BitBlt GameForm.hDC, HorBlit, VerBlit, 40, 57, PicSource(1).hDC, (Map(MapXCoOrd + ((ZArray - 1) * 2), MapYCoOrd + ((ZArray - 1) * 2), ZArray).Tile - 1) * 40, 57, vbSrcAnd
                            BitBlt GameForm.hDC, HorBlit, VerBlit, 40, 57, PicSource(1).hDC, (Map(MapXCoOrd + ((ZArray - 1) * 2), MapYCoOrd + ((ZArray - 1) * 2), ZArray).Tile - 1) * 40, 0, vbSrcPaint
                        End If
                    End If
                    If BlitStatus = 0 And CursorPos.X > HorBlit And CursorPos.X < HorBlit + 40 And CursorPos.Y > VerBlit + 38 And CursorPos.Y < VerBlit + 57 Then
                        BitBlt GameForm.hDC, HorBlit, VerBlit, 40, 57, PicSource(0).hDC, 0, 57, vbSrcAnd
                        BitBlt GameForm.hDC, HorBlit, VerBlit, 40, 57, PicSource(0).hDC, 0, 0, vbSrcPaint
                        BlitStatus = 1
                        OffSetLabel.Caption = MapXCoOrd + ((ZArray - 1) * 2) & " " & MapYCoOrd + ((ZArray - 1) * 2)
                    End If
                Loop
            Loop
        Next ZArray
        'Refresh the screen
        GameForm.Refresh
        Sleep 10
        DoEvents
    Loop
End Sub

'If Q key pressed then quit the program instantly (doesn't exit the loop, just a straight 'End' command)

The problem is, when I move the mouse, the position/movement seems lagged. If I increase the value of Sleep, from say, 10 to 30, it's better. I know that I'm not supposed to use Sleep, but if I remove it, the 'lag' is just as bad, and my PC is a Duron 800! I tested this on my P200 with Sleep being 10, and I got about 1 FPS...hehe.

The form's default cursor is visible, and it isn't lagged. But, the cursor I'm blitting is. It's as if the call I'm using to get the mouse position isn't working.

Can someone please give me some basic code showing how I can have the best performance on any PC? I seem to remember using GetTickCount with DoEvents somehow, to limit FPS, or something like that... (I'm not totally sure how to use DoEvents)

Thanks,

-Git

[HarryW]

At the beginning of your loop, just before the Do, put something like this:

StartTime = GetTickCount

then at the end of your loop, just before the Loop, put something like this:

Do While StartTime + 30 > GetTickCount
Loop
StartTime = GetTickCount

That will make sure each game loop iteration takes at least 30 milliseconds, giving you a framerate of roughly 33 fps.

[kedaman]

Harry, that would slow down it even more, or at least to give any solution to the problem. I'm still not sure about this but bitblt is not processed in the same thread as your application, so when you launch bitblt, next statement will launch before the result has been shown, and therefore building up a huge queue of bitblt's, and also WM_Paint messages for each if you have autoredraw on, which causes the delay.

[git]

Hmm...so how do I fix it? Or is my only option to goto DX/DD?

[kedaman]

you could turn autoredraw off