How do I interpolate 2 animations

[tmighty2]

Hello!

I am dealing with the transitions between 2 states.

I am trying to mimick a Unity transition.

I am experiencing weird color flashes while I expect gradual transitions.
This makes me wonder if I am not aware of a problem.

Thank you for having a look at my code.

This is the code of a cTransition class:

Public Sub UpdateTransition()

    If Not Me.IsActive Then
        Exit Sub
    End If
    
    Dim lNow&
    lNow = GetTickCount

    Dim lTaken&
    lTaken = lNow - m_lStartTime

    Me.Progress = lTaken / GetEffectiveDuration(Me.Duration)
    
    Debug.Print "----------"
    m_s = "Progress: " & Me.Progress & vbNewLine
    
    Clamp Me.Progress, 0, 1

    ' Update animations
    modAnim.UpdateAnimation m_StartAnimationConfig, lNow
    modAnim.UpdateAnimation m_TargetAnimationConfig, lNow
    
    If lTaken >= GetEffectiveDuration(Me.Duration) Then
        ' Transition is complete
        m_bIsTransitionComplete = True
        Me.IsActive = False
        Exit Sub
    End If

    ' Calculate current size using weighted interpolation
    Dim currentSizeStart As Double
    Dim currentSizeTarget As Double
    currentSizeStart = m_StartAnimationConfig.StartSizeFactor + _
                       (m_StartAnimationConfig.TargetSizeFactor - m_StartAnimationConfig.StartSizeFactor) * _
                       Ease(Me.Progress, m_StartAnimationConfig.FunctionType, m_StartAnimationConfig.ModeType)

    currentSizeTarget = m_TargetAnimationConfig.StartSizeFactor + _
                        (m_TargetAnimationConfig.TargetSizeFactor - m_TargetAnimationConfig.StartSizeFactor) * _
                        Ease(Me.Progress, m_TargetAnimationConfig.FunctionType, m_TargetAnimationConfig.ModeType)

    Me.CurrentSize = (currentSizeTarget * Me.Progress) + (currentSizeStart * (1 - Me.Progress))

    ' Calculate current alpha using weighted interpolation
    Dim currentAlphaStart As Double
    Dim currentAlphaTarget As Double
    currentAlphaStart = m_StartAnimationConfig.StartAlpha + _
                        (m_StartAnimationConfig.TargetAlpha - m_StartAnimationConfig.StartAlpha) * _
                        Ease(Me.Progress, m_StartAnimationConfig.FunctionType, m_StartAnimationConfig.ModeType)

    currentAlphaTarget = m_TargetAnimationConfig.StartAlpha + _
                         (m_TargetAnimationConfig.TargetAlpha - m_TargetAnimationConfig.StartAlpha) * _
                         Ease(Me.Progress, m_TargetAnimationConfig.FunctionType, m_TargetAnimationConfig.ModeType)

    Me.CurrentAlpha = (currentAlphaTarget * Me.Progress) + (currentAlphaStart * (1 - Me.Progress))

    ' Calculate current color using BlendColors
    Me.CurrentColor = BlendColors(m_TargetAnimationConfig.TargetColor, m_StartAnimationConfig.StartColor, Me.Progress)

And this is sub to apply the current progress to the size and color of the objects that I want to animate:

Public Function GetEffectiveDuration(ByVal u As Double) As Double

    If g_Slowmo = 0 Then
        g_Slowmo = 1
    End If
    
    GetEffectiveDuration = u * g_Slowmo

End Function

Public Sub UpdateAnimation(ByRef u As cAnimationConfig, ByVal uCurrentTime As Long)

    Dim lDur&
    lDur = uCurrentTime - u.StartTime

    u.DontUseThisForEndResult_Progress = lDur / GetEffectiveDuration(u.Duration) 'GetEffectiveDuration is a helper function to make Duration bigger to slow down the animation for inspecting
    
    'clamp
    Clamp u.DontUseThisForEndResult_Progress, 0, 1

    If u.DontUseThisForEndResult_Progress > 1 Then
        u.DontUseThisForEndResult_Progress = 1
    ElseIf u.DontUseThisForEndResult_Progress < 0 Then
        u.DontUseThisForEndResult_Progress = 0
    End If

    If lDur >= GetEffectiveDuration(u.Duration) Then
    
        u.IsActive = False

        If u.IsOneShot Then
            'can not repeat
            Exit Sub
        Else
            u.IsActive = True 'start again
            u.StartTime = GetTickCount
            'reset and make it play again
            If u.PlayMirroredIfLooped Then
                u.IsPlayingMirrored = Not u.IsPlayingMirrored
            End If
            u.DontUseThisForEndResult_Progress = 0
        End If
    End If
    
    u.EffectiveProgress = modAnim.GetAnimationProgress(u.DontUseThisForEndResult_Progress, u.IsPlayingMirrored)
    u.EasedEffectiveProgress = Ease(u.EffectiveProgress, u.FunctionType, u.ModeType)
    u.CurrentSize = u.SizeFactorAtStart + ((u.SizeFactorAtEnd - u.SizeFactorAtStart) * u.EasedEffectiveProgress)
    u.CurrentColor = BlendColors(u.StartColor, u.TargetColor, 1 - u.EffectiveProgress) 'dont use easing for color, instead use linear
    
End Sub