initial commit, 4.5 stable

thirdparty/jolt_physics/Jolt/Math/FindRoot.h

@@ -0,0 +1,42 @@
+// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
+// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+JPH_NAMESPACE_BEGIN
+
+/// Find the roots of \f$inA \: x^2 + inB \: x + inC = 0\f$.
+/// @return The number of roots, actual roots in outX1 and outX2.
+/// If number of roots returned is 1 then outX1 == outX2.
+template <typename T>
+inline int FindRoot(const T inA, const T inB, const T inC, T &outX1, T &outX2)
+{
+	// Check if this is a linear equation
+	if (inA == T(0))
+	{
+		// Check if this is a constant equation
+		if (inB == T(0))
+			return 0;
+
+		// Linear equation with 1 solution
+		outX1 = outX2 = -inC / inB;
+		return 1;
+	}
+
+	// See Numerical Recipes in C, Chapter 5.6 Quadratic and Cubic Equations
+	T det = Square(inB) - T(4) * inA * inC;
+	if (det < T(0))
+		return 0;
+	T q = (inB + Sign(inB) * sqrt(det)) / T(-2);
+	outX1 = q / inA;
+	if (q == T(0))
+	{
+		outX2 = outX1;
+		return 1;
+	}
+	outX2 = inC / q;
+	return 2;
+}
+
+JPH_NAMESPACE_END