VB2010 - how avoid the '1.#INF'?

[joaquim]

see these functions for RayCasting(yes recreating again):

Private Function GetMapPosition(ByVal Position As Double) As Integer
        Return Math.Floor(Position / ObjectSize)
    End Function

    Private Sub DrawRays()
        Dim RayCount As Integer = 1
        Dim RayIndex As Integer = 0
        Dim RayX As Double = Player.PosX
        Dim RayY As Double = Player.PosY
        Dim RayStepX As Double = 0.0
        Dim RayStepY As Double = 0.0
        Dim RayRadians As Double = Player.Radians '- (DegreeToRadians * 30)
        Dim RayRadiansStep As Double = 0.0
        Dim GridCount As Integer = 0
        Dim aTan As Double = 0.0
        Dim MapX As Integer = 0
        Dim MapY As Integer = 0

        'On Error Resume Next

        For RayIndex = 0 To RayCount
            RayRadians = Player.Radians
            GridCount = 0

            'Check Horizontal Lines:
            aTan = -1 / Math.Tan(RayRadians)
            If (RayRadians > Math.PI) Then
                'Get next Intersection:
                RayY = ((Player.PosY >> 6) << 6) - 0.0001
                RayX = (Player.PosY - RayY) * aTan + Player.PosX
                RayStepY = -ObjectSize
                RayStepX = -RayStepY * aTan
            ElseIf (RayRadians < Math.PI) Then
                'Get next Intersection:
                RayY = ((Player.PosY >> 6) << 6) + ObjectSize
                RayX = (Player.PosY - RayY) * aTan + Player.PosX
                RayStepY = ObjectSize
                RayStepX = -RayStepY * aTan
            ElseIf (RayRadians = 0 Or RayRadians = Math.PI) Then
                RayY = Player.PosY
                RayX = Player.PosX

                Continue For
            End If

            'On Error Resume Next
            Do While (GridCount < 8)

                MapX = GetMapPosition(RayX)
                MapY = GetMapPosition(RayY)
                If (MapLevel0(MapX, MapY) <> Color.Black) Then
                    RayX += RayStepX
                    RayY += RayStepY
                    GridCount += 1
                Else
                    GridCount = 8
                End If
            Loop
            imgLevelMap0Graphics.DrawLine(Pens.Yellow, New Point(Player.PosX, Player.PosY), New Point(Math.Floor(RayX), Math.Floor(RayY)))
        Next
        'Debug.Print(CStr(RayStepX) & vbTab & CStr(RayStepY))
    End Sub

these line:

Return Math.Floor(Position / ObjectSize)

the 'Position' give me '1.#INF'.. it's an error..: "A first chance exception of type 'System.OverflowException' occurred in RayCasting1.exe"
how can i avoid these type of error?
the GetMapPosition() is for give me the array map position(an integer value).

[PlausiblyDamp]

When you get this exception what are the values for Position and ObjectSize?

[OptionBase1]

At no place in your code are you declaring or setting a value of ObjectSize, so we have no idea what type it is or what value(s) it may have when your code runs.

Assuming it is something like a Double, as ObjectSize approaches 0, Position / ObjectSize will approach Infinity. So you will likely need to have some sort of lower bounds check of what the value of ObjectSize is, and if it is too close to 0, you'll need to have different code to handle that situation.

[joaquim]

the 'ObjectSize' is 64.... when the 'RayRadians' is zero..
i can get here:

aTan = -1 / Math.Tan(RayRadians)

because if the 'Math.Tan(RayRadians)' is zero, it will be error\infinite...
other times i can get a much big number
i'm testing more the values and maybe avoiding more errors
to be honest, i'm new with VB2010... so i'm trying understand the errors.. thanks for all
the problem isn't resolved... but i'm trying

[OptionBase1]

Looks like you are calculating a perpendicular slope there. And you have to remember that in the world of the x, y axis, the slope (dy/dx) of a vertical line is infinity, since the x value is constant. So if the original line is horizontal, you need extra code to handle calculations related to the line perpendicular to it, since the "true" slope of that line is infinity.

[joaquim]

is there another way for avoid these several errors\bugs:

Private Function GetMapPosition(ByVal Position As Double) As Integer
        Return Math.Floor(Position / ObjectSize)
    End Function

    Private Sub DrawRays()
        Dim RayCount As Integer = 1
        Dim RayIndex As Integer = 0
        Dim RayX As Double = Player.PosX
        Dim RayY As Double = Player.PosY
        Dim RayStepX As Double = 0.0
        Dim RayStepY As Double = 0.0
        Dim RayRadians As Double = Player.Radians '- (DegreeToRadians * 30)
        Dim RayRadiansStep As Double = 0.0
        Dim GridCount As Integer = 0
        Dim aTan As Double = 0.0
        Dim MapX As Integer = 0
        Dim MapY As Integer = 0



        For RayIndex = 0 To RayCount
            RayRadians = Player.Radians
            GridCount = 0

            'Check Horizontal Lines:
            aTan = -1 / Math.Tan(RayRadians)

            'Get next Intersection:
            If (RayRadians > PI) Then
                RayY = ((Player.PosY >> 6) << 6) - 0.0001
                RayX = (Player.PosY - RayY) * aTan + Player.PosX
                RayStepY = -ObjectSize
                RayStepX = -RayStepY * aTan
            ElseIf (RayRadians < PI) Then
                RayY = ((Player.PosY >> 6) << 6) + ObjectSize
                RayX = (Player.PosY - RayY) * aTan + Player.PosX
                RayStepY = ObjectSize
                RayStepX = -RayStepY * aTan
            ElseIf (RayRadians = 0 Or RayRadians = PI) Then 'no ray
                RayY = Player.PosY
                RayX = Player.PosX
                RayStepY = 0
                RayStepX = 0
                GridCount = 8
            End If

            'Get next Intersections:
            'enter on 'while' if the step is different than zero... and only count 8 steps\adds:
            Do While (RayStepX <> 0 And RayStepY <> 0 And GridCount < 8)
                'avoiding the Ray position be more the map\array size and draw the array:
                If (RayX > (9 * ObjectSize) Or RayY > (9 * ObjectSize)) Then Continue For

                'Get Map Position:
                MapX = GetMapPosition(RayX)
                MapY = GetMapPosition(RayY)

                'Avoid negative and more than 9 index array:
                If (MapX > 9 Or MapY > 9) Then Exit Do
                If (MapX < 0 Or MapY < 0) Then Exit Do

                If (MapLevel0(MapX, MapY) <> Color.Black) Then
                    RayX += RayStepX
                    RayY += RayStepY
                    GridCount += 1
                Else
                    GridCount = 8
                End If
            Loop

            imgLevelMap0Graphics.DrawLine(Pens.Yellow, New Point(Player.PosX, Player.PosY), New Point(Math.Floor(RayX), Math.Floor(RayY)))
        Next

    End Sub

????
even controlling the 'Mapx' and 'Mapy' isn't easy
'9' is the count squares on map\array. by width(9*objectsize) and height((9*objectsize) sizes...

[OptionBase1]

You can't blindly perform a division when the denominator can potentially be 0, and you still are doing that in that code. Your existing aTan calculation must be inside of logic that verifies that the result of Math.Tan(RayRadians) isn't 0. And in the case that it IS 0, I would imagine you would need entirely new logic below that that accommodates a purely "vertical" tangent line.

[joaquim]

updated:

 Private Function GetMapPosition(ByVal Position As Double) As Integer
        Return Math.Floor(Position / ObjectSize)
    End Function

    Private Sub DrawRays()
        Dim RayCount As Integer = 1
        Dim RayIndex As Integer = 0
        Dim RayX As Double = Player.PosX
        Dim RayY As Double = Player.PosY
        Dim RayStepX As Double = 0.0
        Dim RayStepY As Double = 0.0
        Dim RayRadians As Double = Player.Radians '- (DegreeToRadians * 30)
        Dim RayRadiansStep As Double = 0.0
        Dim GridCount As Integer = 0
        Dim aTan As Double = 0.0
        Dim MapX As Integer = 0
        Dim MapY As Integer = 0



        For RayIndex = 0 To RayCount
            RayRadians = Player.Radians
            GridCount = 0

            'Check Horizontal Lines:
            'avoiding division by zero:
            Dim tan As Double = Math.Tan(RayRadians)
            If (tan = 0) Then tan = 1
            aTan = -1 / tan

            'Get next Intersection:
            If (RayRadians > PI) Then
                RayY = ((Player.PosY >> 6) << 6) - 0.0001
                RayX = (Player.PosY - RayY) * aTan + Player.PosX
                RayStepY = -ObjectSize
                RayStepX = -RayStepY * aTan
            ElseIf (RayRadians < PI) Then
                RayY = ((Player.PosY >> 6) << 6) + ObjectSize
                RayX = (Player.PosY - RayY) * aTan + Player.PosX
                RayStepY = ObjectSize
                RayStepX = -RayStepY * aTan
            ElseIf (RayRadians = 0 Or RayRadians = PI) Then 'no ray
                RayY = Player.PosY
                RayX = Player.PosX
                RayStepY = 0
                RayStepX = 0
                GridCount = 8
                Continue For
            End If

            'Get next Intersections:
            'enter on 'while' if the step is different than zero... and only count 8 steps\adds:
            Do While (RayStepX <> 0 And RayStepY <> 0 And GridCount < 8)
                'avoiding the Ray position be more the map\array size and draw the array:
                If (RayX > (9 * ObjectSize) Or RayY > (9 * ObjectSize)) Then Continue For

                'Get Map Position:
                MapX = GetMapPosition(RayX)
                MapY = GetMapPosition(RayY)

                'Avoid negative and more than 9 index array:
                If (MapX > 9 Or MapY > 9) Then Exit Do
                If (MapX < 0 Or MapY < 0) Then Exit Do

                If (MapLevel0(MapX, MapY) <> Color.Black) Then
                    RayX += RayStepX
                    RayY += RayStepY
                    GridCount += 1
                Else
                    GridCount = 8
                End If
            Loop

           If (RayX <> Player.PosX Or RayY <> Player.PosY) Then imgLevelMap0Graphics.DrawLine(Pens.Yellow, New Point(Player.PosX, Player.PosY), New Point(Math.Floor(RayX), Math.Floor(RayY)))
        Next

    End Sub