Fix 'dtRandomPointInConvexPoly()' returning a garbage value if s == 1.0f. (#271)

Detour/Source/DetourCommon.cpp

@@ -342,8 +342,8 @@ void dtRandomPointInConvexPoly(const float* pts, const int npts, float* areas,
 	// Find sub triangle weighted by area.
 	const float thr = s*areasum;
 	float acc = 0.0f;
-	float u = 0.0f;
+	float u = 1.0f;
-	int tri = 0;
+	int tri = npts - 1;
 	for (int i = 2; i < npts; i++) {
 		const float dacc = areas[i];
 		if (thr >= acc && thr < (acc+dacc))

RecastDemo/Source/NavMeshTesterTool.cpp

@@ -45,7 +45,7 @@
 // Uncomment this to dump all the requests in stdout.
 #define DUMP_REQS
 
-// Returns a random number [0..1)
+// Returns a random number [0..1]
 static float frand()
 {
 //	return ((float)(rand() & 0xffff)/(float)0xffff);

RecastDemo/premake5.lua

@@ -202,6 +202,8 @@ project "Tests"
 		"../Tests/*.cpp",
 		"../Tests/Recast/*.h",
 		"../Tests/Recast/*.cpp",
+		"../Tests/Detour/*.h",
+		"../Tests/Detour/*.cpp",
 	}
 
 	-- project dependencies

Tests/Detour/Tests_Detour.cpp

@@ -0,0 +1,33 @@
+#include "catch.hpp"
+
+#include "DetourCommon.h"
+
+TEST_CASE("dtRandomPointInConvexPoly")
+{
+	SECTION("Properly works when the argument 's' is 1.0f")
+	{
+		const float pts[] = {
+			0, 0, 0,
+			0, 0, 1,
+			1, 0, 0,
+		};
+		const int npts = 3;
+		float areas[6];
+		float out[3];
+
+		dtRandomPointInConvexPoly(pts, npts, areas, 0.0f, 1.0f, out);
+		REQUIRE(out[0] == 0);
+		REQUIRE(out[1] == 0);
+		REQUIRE(out[2] == 1);
+
+		dtRandomPointInConvexPoly(pts, npts, areas, 0.5f, 1.0f, out);
+		REQUIRE(out[0] == 1.0f / 2);
+		REQUIRE(out[1] == 0);
+		REQUIRE(out[2] == 1.0f / 2);
+
+		dtRandomPointInConvexPoly(pts, npts, areas, 1.0f, 1.0f, out);
+		REQUIRE(out[0] == 1);
+		REQUIRE(out[1] == 0);
+		REQUIRE(out[2] == 0);
+	}
+}