Question

Ok so I am trying to make a third person game in VB6 for a class project, and when the person collides with a Wall (shape) then they shouldnt move. But the problem is, when the person collides into the wall, it stops, however now the wall is now stuck and wont scroll along with all the other walls. Here is my code:

Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
    If KeyCode = vbKeyLeft Or vbKeyRight Or vbKeyUp Or vbKeyDown Then
        tmrMove.Enabled = True
    End If

    Select Case KeyCode
        Case vbKeyLeft
            XVel = 0 - Speed
            YVel = 0
        Case vbKeyRight
            XVel = Speed
            YVel = 0
        Case vbKeyUp
            YVel = 0 - Speed
            XVel = 0
        Case vbKeyDown
            YVel = Speed
            XVel = 0
    End Select

    Keys(KeyCode) = True
End Sub

Private Sub Form_KeyUp(KeyCode As Integer, Shift As Integer)
    Keys(KeyCode) = False
    If Keys(vbKeyLeft) = False And Keys(vbKeyRight) = False And Keys(vbKeyUp) = False And Keys(vbKeyDown) = False Then
        XVel = 0
        YVel = 0
    End If
End Sub


Private Sub tmrMove_Timer()
    For i = 0 To (Wall.Count - 1)
        If Collision(Character, Wall(i)) = False Then
            Wall(i).Left = Wall(i).Left - XVel
            Wall(i).Top = Wall(i).Top - YVel
        End If
    Next i
End Sub


Public Function Collision(Shape1 As ShockwaveFlash, Shape2 As Shape) As Boolean
    If (Shape1.Left + Shape1.Width) > Shape2.Left And _
    Shape1.Left < (Shape2.Left + Shape2.Width) And _
    (Shape1.Top + Shape1.Height) > Shape2.Top And _
    Shape1.Top < (Shape2.Top + Shape2.Height) Then
        Collision = True
    Else
        Collision = False
    End If
End Function

Now as you can see, the problem is that when it collides, I dont know howto “uncollide” so the wall that we collided with becomes stuck and will not scroll with the rest of the things. It is confusing to explain hopefully you understand. Thanks

As you can see,

Answer 1

The most straightforward way to fix your collision logic is to consider the questions:

• Can I move up?
• Can I move down?
• Can I move left?
• Can I move right?

rather than the question “am I in a collision with the wall?”

You answer those questions by comparing your post-move position to the limit imposed by the wall.

Code example (be kind… I didn’t write VB6 for the last 10 years 😉

Public Function CanMoveLeft(Shape1 As ShockwaveFlash, Shape2 As Shape) As Boolean
    If (Shape1.Left + Shape1.Width) > Shape2.Right) 
    Then
        CanMoveLeft = True
    Else
        CanMoveLeft = False
    End If
End Function

This example presumes you have already applied a proposed new position to Shape1. If you prefer, you can pass in the unmoved Shape1 along with the leftward velocity and modify the calculation accordingly. I think you probably want to compare the left edge of the shape to the right edge of the wall rather than the left edge of the wall in your code sample.

Note that if your post-move position would place you inside the wall, you would want to adjust the actual position to be just inside the room (if you’re moving more than one pixel per frame, your velocity can put your current position inside or beyond the wall).