AnimNodeAlphaOptions.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Animation/AnimInstance.h"
#include "Animation/AnimInstanceProxy.h"
#include "Animation/AnimNodeBase.h"
#include "Animation/InputScaleBias.h"
 
// Alpha blending options helper functions for anim nodes
// Assumes that the specified node contains the members:
// AlphaInputType, ActualAlpha, AlphaScaleBias, Alpha, bAlphaBoolEnabled, AlphaCurveName
struct FAnimNodeAlphaOptions
{
    // Per-tick update
    template<typename AnimNodeType>
    static bool Update(AnimNodeType& InAnimNode, const FAnimationUpdateContext& InContext)
    {
        // Determine Actual Alpha.
        switch (InAnimNode.AlphaInputType)
        {
        case EAnimAlphaInputType::Float:
            InAnimNode.ActualAlpha = InAnimNode.AlphaScaleBias.ApplyTo(InAnimNode.AlphaScaleBiasClamp.ApplyTo(InAnimNode.Alpha, InContext.GetDeltaTime()));
            break;
        case EAnimAlphaInputType::Bool:
            InAnimNode.ActualAlpha = InAnimNode.AlphaBoolBlend.ApplyTo(InAnimNode.bAlphaBoolEnabled, InContext.GetDeltaTime());
            break;
        case EAnimAlphaInputType::Curve:
            if (UAnimInstance* AnimInstance = Cast<UAnimInstance>(InContext.AnimInstanceProxy->GetAnimInstanceObject()))
            {
                InAnimNode.ActualAlpha = InAnimNode.AlphaScaleBiasClamp.ApplyTo(AnimInstance->GetCurveValue(InAnimNode.AlphaCurveName), InContext.GetDeltaTime());
            }
            break;
        };
 
        // Make sure Alpha is clamped between 0 and 1.
        InAnimNode.ActualAlpha = FMath::Clamp<float>(InAnimNode.ActualAlpha, 0.f, 1.f);
 
        return FAnimWeight::IsRelevant(InAnimNode.ActualAlpha);
    }
};