Recast: add helper functions for ledge spans

rdCalcMaxLOSAngle: calculate max angle before LOS gets blocked.
rdCalcLedgeSpanOffsetAmount: calculate offset towards ledge to keep object in LOS.

src/thirdparty/recast/Shared/Include/SharedCommon.h

@@ -454,6 +454,19 @@ void rdPerpDirEdge2D(const float* dir, const bool inner, float* out);
 ///  @param[out]	out		The resulting direction. [(x, y)]
 void rdPerpDirPtEdge2D(const float* v1, const float* v2, const bool inner, float* out);
 
+/// 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.
+/// @return The maximum angle before LOS gets blocked.
+float rdCalcMaxLOSAngle(const float ledgeSpan, const float objectHeight);
+
+/// Determines the amount we need to offset an object to maintain LOS from an angle, with a maximum.
+///  @param[in]		ledgeSpan	The distance between the edge of the object and the edge of the ledge.
+///  @param[in]		slopeAngle	The slope angle to test.
+///  @param[in]		maxAngle	The maximum angle in degrees.
+/// @return The amount we need to offset to maintain LOS.
+float rdCalcLedgeSpanOffsetAmount(const float ledgeSpan, const float slopeAngle, const float maxAngle);
+
 unsigned char rdClassifyPointOutsideBounds(const float* pt, const float* bmin, const float* bmax);
 unsigned char rdClassifyPointInsideBounds(const float* pt, const float* bmin, const float* bmax);
 

src/thirdparty/recast/Shared/Source/SharedCommon.cpp

@@ -432,6 +432,22 @@ void rdPerpDirPtEdge2D(const float* v1, const float* v2, const bool inner, float
 	rdPerpDirEdge2D(dir, inner, out);
 }
 
+float rdCalcMaxLOSAngle(const float ledgeSpan, const float objectHeight)
+{
+	const float angleRad = rdMathAtan2f(objectHeight, ledgeSpan);
+	const float angleDeg = angleRad * (180.0f/RD_PI);
+
+	return angleDeg;
+}
+
+float rdCalcLedgeSpanOffsetAmount(const float ledgeSpan, const float slopeAngle, const float maxAngle)
+{
+	const float clampedAngle = rdClamp(slopeAngle, slopeAngle, maxAngle);
+	const float offset = ledgeSpan * (clampedAngle / maxAngle);
+
+	return offset;
+}
+
 static const unsigned char XP = 1 << 0;
 static const unsigned char ZP = 1 << 1;
 static const unsigned char XM = 1 << 2;