Functions: add squareroot linear function

src/lib/mathlib/math/Functions.hpp

@@ -172,4 +172,30 @@ const T gradual3(const T &value,
 	}
 }
 
+/*
+ * Squareroot, linear function with fixed corner point at intersection (1,1)
+ *                     /
+ *      linear        /
+ *                   /
+ * 1                /
+ *                /
+ *      sqrt     |
+ *              |
+ * 0     -------
+ *             0    1
+ */
+template<typename T>
+const T sqrt_linear(const T &value)
+{
+	if (value < static_cast<T>(0)) {
+		return static_cast<T>(0);
+
+	} else if (value < static_cast<T>(1)) {
+		return sqrtf(value);
+
+	} else {
+		return value;
+	}
+}
+
 } /* namespace math */

src/lib/mathlib/math/FunctionsTest.cpp

@@ -183,3 +183,14 @@ TEST(FunctionsTest, gradual3)
 				 0.f, .5f, 1.5f,
 				 1.f, 2.f, 3.f), 3.f);
 }
+
+TEST(FunctionsTest, sqrt_linear)
+{
+	EXPECT_FLOAT_EQ(sqrt_linear(-12.f), 0.f);
+	EXPECT_FLOAT_EQ(sqrt_linear(-2.f), 0.f);
+	EXPECT_FLOAT_EQ(sqrt_linear(0.f), 0.f);
+	EXPECT_FLOAT_EQ(sqrt_linear(.5f), 0.70710678f);
+	EXPECT_FLOAT_EQ(sqrt_linear(1.f), 1.f);
+	EXPECT_FLOAT_EQ(sqrt_linear(2.f), 2.f);
+	EXPECT_FLOAT_EQ(sqrt_linear(120.f), 120.f);
+}