'////////////////// Shading section //////////////////////////////////
Public Sub DrSetLightVector(ByRef lVector As m3Vector)
    Dim L As Single
    L = m3VectorLen(lVector)
    If L < 0.000001 Then
        lightVector.x = 0
        lightVector.Y = 0
        lightVector.Z = 1
    Else
        lightVector.x = lVector.x / L
        lightVector.Y = lVector.Y / L
        lightVector.Z = lVector.Z / L
    End If
End Sub

Public Function DrGetLightVector() As m3Vector
    DrGetLightVector = lightVector
End Function

Public Sub DrApplyLightVector(ByRef M As m3Matrix)
    m3VectorApply lightVector, M
End Sub
'Draw the solid object width Shading on the object
Public Sub Solid3DShadingDraw(ByRef Obj As Object, ByRef S As Solid3D, ByVal Border As Boolean)
    Dim i As Integer
    Dim j As Integer
    Dim f As Single
    Dim v As m3Vector
    Dim u As m3Vector
    Dim n As m3Vector
    Dim nVerts As Integer
    Dim p1 As Integer
    Dim p2 As Integer
    Dim P3 As Integer
    
    '********** Shading Factors*******************************
    Dim color As Long
    Dim ColorTo As Long
    Dim BorderColor As Long
    Dim R As Byte
    Dim G As Byte
    Dim B As Byte
    Dim maxRGB As Byte
    Dim dot As Single
    Dim dotMax As Single
    '*************************************************************
    '********** Shading Init Factors*******************************
    color = Obj.FillColor
    BorderColor = Obj.ForeColor
    'Resolve Fill Color Into RGB Components
    R = &HFF& And color
    G = (&HFF00& And color) \ &H100&
    B = (&HFF0000 And color) \ &H10000
    'Compute Maximum Componen Of RGB Components
    maxRGB = R
    If G > maxRGB Then maxRGB = G
    If B > maxRGB Then maxRGB = B
    'Compute Maximum Factor Of RGB Components
    dotMax = maxRGB / 255
    
    'Ambient Light is some non-directional light in the environment
    ' (background light).
    ' Ambient Light Factor is 0.2
    dotMax = dotMax + AmbFactor
    If dotMax * maxRGB > 255 Then dotMax = 255 / maxRGB
    
    
    
    Xorg = Abs(Obj.ScaleLeft)
    Yorg = Abs(Obj.ScaleTop)
    Select Case Projec
    Case Parallel
        For i = 1 To S.nVerts
            ST(i) = S.Verts(i)
        Next i
    Case Perspective
        For i = 1 To S.nVerts
            f = Dist / (Dist - S.Verts(i).Z)
            ST(i).x = S.Verts(i).x * f
            ST(i).Y = S.Verts(i).Y * f
            ST(i).Z = S.Verts(i).Z
        Next i
    End Select
    
    
    For i = 1 To S.nFaces
        p1 = S.Faces(i).Face(1)
        p2 = S.Faces(i).Face(2)
        P3 = S.Faces(i).Face(3)
        v = m3VectorInit(ST(p1), ST(p2))
        u = m3VectorInit(ST(p2), ST(P3))
        n = m3VectorCross(v, u)
        nVerts = S.Faces(i).nVerts
        If n.Z > 0 Then
            For j = 1 To nVerts
                p1 = S.Faces(i).Face(j)
                Poly2D(j).x = Xorg + ST(p1).x
                Poly2D(j).Y = Yorg - ST(p1).Y
            Next j
            m3VectorSetLen 1, n
            dot = lightVector.x * n.x + lightVector.Y * n.Y + lightVector.Z * n.Z
            If dot > 0.0000001 Then
                dot = dot + AmbFactor
             Else
                dot = AmbFactor
            End If
            If dot > dotMax Then dot = dotMax
            ColorTo = RGB(dot * R, dot * G, dot * B)
            Obj.FillColor = ColorTo
            If Not Border Then
                Obj.ForeColor = ColorTo
            End If
            Polygon Obj.hdc, Poly2D(1), nVerts
            
        End If
        
    Next i
    
    ' Restore Object's Colors
    Obj.FillColor = color
    Obj.ForeColor = BorderColor
End Sub
'Aplly view of Polygon 3D to 2D
Private Sub ProjectM3Points(ByVal nVerts As Integer, ByRef P() As m3Point)
    Dim f As Single
    Dim i As Integer
    Select Case Projec
        Case Parallel
            For i = 1 To nVerts
                Poly2D(i).x = Xorg + P(i).x
                Poly2D(i).Y = Yorg - P(i).Y
            Next i
        Case Perspective
            For i = 1 To nVerts
                f = Dist / (Dist - P(i).Z)
                Poly2D(i).x = Xorg + f * P(i).x
                Poly2D(i).Y = Yorg - f * P(i).Y
            Next i
    End Select
End Sub

'Draw and fill the polygon width Shading on the object
Public Sub Poly3DShadingFill(ByRef Obj As Object, ByRef P As Poly3D, ByVal Border As Boolean)
    Dim i As Integer
    Dim p1 As m3Point
    Dim p2 As m3Point
    Dim P3 As m3Point
    Dim n As m3Vector
    Dim v As m3Vector
    Dim u As m3Vector
    Dim f As Single
    '********** Shading Factors*******************************
    Dim color As Long
    Dim ColorTo As Long
    Dim BorderColor As Long
    Dim R As Byte
    Dim G As Byte
    Dim B As Byte
    Dim maxRGB As Byte
    Dim dot As Single
    Dim dotMax As Single
    '*************************************************************
    '********** Shading Init Factors*******************************
    color = Obj.FillColor
    BorderColor = Obj.ForeColor
    'Resolve Fill Color Into RGB Components
    R = &HFF& And color
    G = (&HFF00& And color) \ &H100&
    B = (&HFF0000 And color) \ &H10000
    'Compute Maximum Componen Of RGB Components
    maxRGB = R
    If G > maxRGB Then maxRGB = G
    If B > maxRGB Then maxRGB = B
    'Compute Maximum Factor Of RGB Components
    dotMax = maxRGB / 255
    
    'Ambient Light is some non-directional light in the environment
    ' (background light).
    ' Ambient Light Factor is 0.2
    dotMax = dotMax + AmbFactor
    If dotMax * maxRGB > 255 Then dotMax = 255 / maxRGB
    
    Xorg = Abs(Obj.ScaleLeft)
    Yorg = Abs(Obj.ScaleTop)
    Select Case Projec
    Case Parallel
        p1 = P.Verts(1)
        p2 = P.Verts(2)
        P3 = P.Verts(3)
    Case Perspective
        f = Dist / (Dist - P.Verts(1).Z)
        p1.x = P.Verts(1).x * f
        p1.Y = P.Verts(1).Y * f
        p1.Z = P.Verts(1).Z
        
        f = Dist / (Dist - P.Verts(2).Z)
        p2.x = P.Verts(2).x * f
        p2.Y = P.Verts(2).Y * f
        p2.Z = P.Verts(2).Z
        
        f = Dist / (Dist - P.Verts(3).Z)
        P3.x = P.Verts(3).x * f
        P3.Y = P.Verts(3).Y * f
        P3.Z = P.Verts(3).Z
    End Select
    v = m3VectorInit(p1, p2)
    u = m3VectorInit(p2, P3)
    n = m3VectorCross(v, u)
    If n.Z < 0 Then
        n.Y = -n.Y
        n.x = -n.x
        n.Z = -n.Z
    End If
       
   
    m3VectorSetLen 1, n
    dot = lightVector.x * n.x + lightVector.Y * n.Y + lightVector.Z * n.Z
    dot = dot + AmbFactor
    If dot > dotMax Then dot = dotMax
    ColorTo = RGB(dot * R, dot * G, dot * B)
    Obj.FillColor = ColorTo
    If Not Border Then
        Obj.ForeColor = ColorTo
    End If
    ProjectM3Points P.nVerts, P.Verts
    Polygon Obj.hdc, Poly2D(1), P.nVerts

    ' Restore Object's Colors
    Obj.FillColor = color
    Obj.ForeColor = BorderColor
End Sub