diff --git a/src/thirdparty/recast/Shared/Include/SharedCommon.h b/src/thirdparty/recast/Shared/Include/SharedCommon.h
index 548754c5..b7328171 100644
--- a/src/thirdparty/recast/Shared/Include/SharedCommon.h
+++ b/src/thirdparty/recast/Shared/Include/SharedCommon.h
@@ -488,6 +488,15 @@ void rdCalcEdgeNormal2D(const float* dir, const bool inner, float* out);
 ///  @param[out]	out		The resulting normal. [(x, y)]
 void rdCalcEdgeNormalPt2D(const float* v1, const float* v2, const bool inner, float* out);
 
+///  @param[in]		edgeStart		First vert of the polygon edge. [(x, y, z)]
+///  @param[in]		edgeEnd			Second vert of the polygon edge. [(x, y, z)]
+///  @param[in]		subEdgeStart	First vert of the detail edge. [(x, y, z)]
+///  @param[in]		subEdgeEnd		Second vert of the detail edge. [(x, y, z)]
+///  @param[out]	tmin			The normalized distance ratio from polygon edge start to detail edge start.
+///  @param[out]	tmax			The normalized distance ratio from polygon edge start to detail edge end.
+bool rdCalcSubEdgeArea2D(const float* edgeStart, const float* edgeEnd, const float* subEdgeStart,
+	const float* subEdgeEnd, float& tmin, float& tmax);
+
 /// Derives the maximum angle in which an object on an elevated surface can be seen from below.
 ///  @param[in]		ledgeSpan		The distance between the edge of the object and the edge of the ledge.
 ///  @param[in]		objectHeight	The height of the object.
diff --git a/src/thirdparty/recast/Shared/Source/SharedCommon.cpp b/src/thirdparty/recast/Shared/Source/SharedCommon.cpp
index b2f3c6c9..a8821816 100644
--- a/src/thirdparty/recast/Shared/Source/SharedCommon.cpp
+++ b/src/thirdparty/recast/Shared/Source/SharedCommon.cpp
@@ -432,6 +432,28 @@ void rdCalcEdgeNormalPt2D(const float* v1, const float* v2, const bool invert, f
 	rdCalcEdgeNormal2D(dir, invert, out);
 }
 
+bool rdCalcSubEdgeArea2D(const float* edgeStart, const float* edgeEnd, const float* subEdgeStart,
+	const float* subEdgeEnd, float& tmin, float& tmax)
+{
+	const float edgeLen = rdVdist2D(edgeStart, edgeEnd);
+	const float subEdgeStartDist = rdVdist2D(edgeStart, subEdgeStart);
+	const float subEdgeEndDist = rdVdist2D(edgeStart, subEdgeEnd);
+
+	tmin = subEdgeStartDist / edgeLen;
+	tmax = subEdgeEndDist / edgeLen;
+
+	// note(amos): If the min is larger than the max, we most likely have a
+	// malformed detail polygon, e.g. a triangle that is flipped causing its
+	// boundary edge's start vert to be closer to the end vert of the polygon
+	// when comparing the distances in the same winding order. This can happen
+	// on more complex geometry or when the error tollerance is raised. Either
+	// way return false to notify caller that the calculation has failed.
+	if (tmin > tmax)
+		return false;
+
+	return true;
+}
+
 float rdCalcMaxLOSAngle(const float ledgeSpan, const float objectHeight)
 {
 	const float angleRad = rdMathAtan2f(objectHeight, ledgeSpan);