From aa2eeb82437363680415e83562a83bbf64d291d3 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Tue, 26 Jan 2021 12:32:35 +0100
Subject: [PATCH] Add GetSplineDirection util to Spline

---
 Source/Engine/Level/Actors/Spline.cpp | 15 +++++++++++++++
 Source/Engine/Level/Actors/Spline.h   | 14 ++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/Source/Engine/Level/Actors/Spline.cpp b/Source/Engine/Level/Actors/Spline.cpp
index 4c2680e79..9f47aa06e 100644
--- a/Source/Engine/Level/Actors/Spline.cpp
+++ b/Source/Engine/Level/Actors/Spline.cpp
@@ -77,6 +77,21 @@ Transform Spline::GetSplineLocalTransform(float time) const
     return t;
 }
 
+Vector3 Spline::GetSplineDirection(float time) const
+{
+    return _transform.LocalToWorldVector(GetSplineLocalDirection(time));
+}
+
+Vector3 Spline::GetSplineLocalDirection(float time) const
+{
+    if (Curve.GetKeyframes().Count() == 0)
+        return Vector3::Forward;
+    Transform t;
+    Curve.EvaluateFirstDerivative(t, time, _loop);
+    t.Translation.Normalize();
+    return t.Translation;
+}
+
 Vector3 Spline::GetSplinePoint(int32 index) const
 {
     CHECK_RETURN(index >= 0 && index < GetSplinePointsCount(), Vector3::Zero)
diff --git a/Source/Engine/Level/Actors/Spline.h b/Source/Engine/Level/Actors/Spline.h
index fd489b823..cc4226414 100644
--- a/Source/Engine/Level/Actors/Spline.h
+++ b/Source/Engine/Level/Actors/Spline.h
@@ -96,6 +96,20 @@ public:
     /// <returns>The calculated curve point transformation (local-space).</returns>
     API_FUNCTION() Transform GetSplineLocalTransform(float time) const;
 
+    /// <summary>
+    /// Evaluates the spline curve direction (forward vector, aka position 1st derivative) at the given time in 3D (world-space).
+    /// </summary>
+    /// <param name="time">The time value. Can be negative or larger than curve length (curve will loop or clamp).</param>
+    /// <returns>The calculated curve direction (world-space).</returns>
+    API_FUNCTION() Vector3 GetSplineDirection(float time) const;
+
+    /// <summary>
+    /// Evaluates the spline curve direction (forward vector, aka position 1st derivative) at the given time in 3D (local-space).
+    /// </summary>
+    /// <param name="time">The time value. Can be negative or larger than curve length (curve will loop or clamp).</param>
+    /// <returns>The calculated curve direction (local-space).</returns>
+    API_FUNCTION() Vector3 GetSplineLocalDirection(float time) const;
+
     /// <summary>
     /// Evaluates the spline curve at the given index (world-space).
     /// </summary>