From 9e88189238b62dc4f6e3e01fb2c65b31404c16d0 Mon Sep 17 00:00:00 2001
From: ragnarok-clanker <ragnarok-clanker>
Date: Wed, 28 Oct 2026 19:44:33 +0000
Subject: [PATCH] Decompile fn_19766 (CalculateVectorAngle)

Batch #1612 by eAthena: 0 byte-identical, 1 confirmed by peer review.

- fn_19766 CalculateVectorAngle: logic confirmed by peer review

Reviewed-by: ragnarok-clanker
---
 Source/Contents/Effects/EffectPrimitiveState.cpp | 15 +++++++++++++++
 Source/Contents/Effects/EffectPrimitiveState.h   |  2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Source/Contents/Effects/EffectPrimitiveState.cpp b/Source/Contents/Effects/EffectPrimitiveState.cpp
index 0330d01..d8f412c 100644
--- a/Source/Contents/Effects/EffectPrimitiveState.cpp
+++ b/Source/Contents/Effects/EffectPrimitiveState.cpp
@@ -179,6 +179,21 @@ void EffectPrimitiveState::GetColorOverride(unsigned char* red, unsigned char* g
 }
 
 // OFFSET: 0x00BAE4B0
+// FUNCTION: fn_19766
+void __stdcall CalculateVectorAngle(float x, float y, std::int16_t* angle) {
+  const float length = SquareRoot(x * x + y * y);
+  const float normalY = y / length;
+  const float normalX = x / length;
+
+  for (std::int16_t index = 0; index <= 180; ++index) {
+    if (normalX >= ClientCosine(index)) {
+      *angle = normalY < 0.0f ? 360 - index : index;
+      return;
+    }
+  }
+
+  *angle = 180;
+}
 
 // OFFSET: 0x00BAE5D0
 // FUNCTION: fn_19767
diff --git a/Source/Contents/Effects/EffectPrimitiveState.h b/Source/Contents/Effects/EffectPrimitiveState.h
index 336cc4b..a3b8c52 100644
--- a/Source/Contents/Effects/EffectPrimitiveState.h
+++ b/Source/Contents/Effects/EffectPrimitiveState.h
@@ -175,7 +175,7 @@ struct EffectPrimitiveObject {
   bool AdvanceFrame();
 };
 
-void CalculateVectorAngle(float x, float y, std::int16_t* angle);
+void __stdcall CalculateVectorAngle(float x, float y, std::int16_t* angle);
 
 static_assert(sizeof(EffectVector3) == 12);
 static_assert(sizeof(EffectPrimitiveRecord) == 140);