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Source/Engine/Animations/AlphaBlend.h

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+// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.
+
+#pragma once
+
+#include "Engine/Core/Math/Math.h"
+
+/// <summary>
+/// Alpha blending modes.
+/// </summary>
+API_ENUM() enum class AlphaBlendMode : byte
+{
+    /// <summary>
+    /// Linear interpolation.
+    /// </summary>
+    Linear = 0,
+
+    /// <summary>
+    /// Cubic-in interpolation.
+    /// </summary>
+    Cubic,
+
+    /// <summary>
+    /// Hermite-Cubic.
+    /// </summary>
+    HermiteCubic,
+
+    /// <summary>
+    /// Sinusoidal interpolation.
+    /// </summary>
+    Sinusoidal,
+
+    /// <summary>
+    /// Quadratic in-out interpolation.
+    /// </summary>
+    QuadraticInOut,
+
+    /// <summary>
+    /// Cubic in-out interpolation.
+    /// </summary>
+    CubicInOut,
+
+    /// <summary>
+    /// Quartic in-out interpolation.
+    /// </summary>
+    QuarticInOut,
+
+    /// <summary>
+    /// Quintic in-out interpolation.
+    /// </summary>
+    QuinticInOut,
+
+    /// <summary>
+    /// Circular-in interpolation.
+    /// </summary>
+    CircularIn,
+
+    /// <summary>
+    /// Circular-out interpolation.
+    /// </summary>
+    CircularOut,
+
+    /// <summary>
+    /// Circular in-out interpolation.
+    /// </summary>
+    CircularInOut,
+
+    /// <summary>
+    /// Exponential-in interpolation.
+    /// </summary>
+    ExpIn,
+
+    /// <summary>
+    /// Exponential-Out interpolation.
+    /// </summary>
+    ExpOut,
+
+    /// <summary>
+    /// Exponential in-out interpolation.
+    /// </summary>
+    ExpInOut,
+};
+
+/// <summary>
+/// Alpha blending utilities.
+/// </summary>
+class AlphaBlend
+{
+public:
+
+    /// <summary>
+    /// Converts the input alpha value from a linear 0-1 value into the output alpha described by blend mode.
+    /// </summary>
+    /// <param name="alpha">The alpha (normalized to 0-1).</param>
+    /// <param name="mode">The mode.</param>
+    /// <returns>The output alpha (normalized to 0-1).</returns>
+    static float Process(float alpha, AlphaBlendMode mode)
+    {
+        switch (mode)
+        {
+        case AlphaBlendMode::Sinusoidal:
+            alpha = (Math::Sin(alpha * PI - PI_HALF) + 1.0f) / 2.0f;
+            break;
+        case AlphaBlendMode::Cubic:
+            alpha = Math::CubicInterp<float>(0.0f, 0.0f, 1.0f, 0.0f, alpha);
+            break;
+        case AlphaBlendMode::QuadraticInOut:
+            alpha = Math::InterpEaseInOut<float>(0.0f, 1.0f, alpha, 2);
+            break;
+        case AlphaBlendMode::CubicInOut:
+            alpha = Math::InterpEaseInOut<float>(0.0f, 1.0f, alpha, 3);
+            break;
+        case AlphaBlendMode::HermiteCubic:
+            alpha = Math::SmoothStep(0.0f, 1.0f, alpha);
+            break;
+        case AlphaBlendMode::QuarticInOut:
+            alpha = Math::InterpEaseInOut<float>(0.0f, 1.0f, alpha, 4);
+            break;
+        case AlphaBlendMode::QuinticInOut:
+            alpha = Math::InterpEaseInOut<float>(0.0f, 1.0f, alpha, 5);
+            break;
+        case AlphaBlendMode::CircularIn:
+            alpha = Math::InterpCircularIn<float>(0.0f, 1.0f, alpha);
+            break;
+        case AlphaBlendMode::CircularOut:
+            alpha = Math::InterpCircularOut<float>(0.0f, 1.0f, alpha);
+            break;
+        case AlphaBlendMode::CircularInOut:
+            alpha = Math::InterpCircularInOut<float>(0.0f, 1.0f, alpha);
+            break;
+        case AlphaBlendMode::ExpIn:
+            alpha = Math::InterpExpoIn<float>(0.0f, 1.0f, alpha);
+            break;
+        case AlphaBlendMode::ExpOut:
+            alpha = Math::InterpExpoOut<float>(0.0f, 1.0f, alpha);
+            break;
+        case AlphaBlendMode::ExpInOut:
+            alpha = Math::InterpExpoInOut<float>(0.0f, 1.0f, alpha);
+            break;
+        default: ;
+        }
+
+        return Math::Saturate<float>(alpha);
+    }
+};