Merge pull request #320 from CesiumGS/math-roundupdown

CHANGES.md

@@ -9,6 +9,7 @@
 ##### Additions :tada:
 
 - Added `Future<T>::share`, which returns a `SharedFuture<T>` and allows multiple continuations to be attached.
+- Added `Math::roundUp` and `Math::roundDown`.
 - Added `Rectangle::computeUnion`.
 
 ### v0.6.0 - 2021-08-02

CesiumUtility/include/CesiumUtility/Math.h

@@ -395,6 +395,46 @@ public:
 
     return simplified;
   };
+
+  /**
+   * @brief Rounds a value up to the nearest integer, like `ceil`, except
+   * that if the value is very close to the lower integer it is rounded down
+   * (like `floor`) instead.
+   *
+   * @param value The value to round.
+   * @param tolerance The tolerance. If the value is closer than this to the
+   * lower integer, it is rounded down instead.
+   * @return The rounded value.
+   */
+  static double roundUp(double value, double tolerance) {
+    double up = glm::ceil(value);
+    double down = glm::floor(value);
+    if (value - down < tolerance) {
+      return down;
+    } else {
+      return up;
+    }
+  }
+
+  /**
+   * @brief Rounds a value down to the nearest integer, like `floor`, except
+   * that if the value is very close to the higher integer it is rounded up
+   * (like `ceil`) instead.
+   *
+   * @param value The value to round.
+   * @param tolerance The tolerance. If the value is closer than this to the
+   * higher integer, it is rounded up instead.
+   * @return The rounded value.
+   */
+  static double roundDown(double value, double tolerance) {
+    double up = glm::ceil(value);
+    double down = glm::floor(value);
+    if (up - value < tolerance) {
+      return up;
+    } else {
+      return down;
+    }
+  }
 };
 
 } // namespace CesiumUtility

CesiumUtility/test/TestMath.cpp

@@ -50,3 +50,23 @@ TEST_CASE("Math::convertLongitudeRange example") {
   //! [convertLongitudeRange]
   CHECK(longitude == CesiumUtility::Math::degreesToRadians(-90.0));
 }
+
+TEST_CASE("Math::roundUp and roundDown") {
+  CHECK(Math::roundUp(1.0, 0.01) == 1.0);
+  CHECK(Math::roundDown(1.0, 0.01) == 1.0);
+
+  CHECK(Math::roundUp(1.01, 0.01) == 2.0);
+  CHECK(Math::roundDown(1.99, 0.01) == 1.0);
+
+  CHECK(Math::roundUp(1.005, 0.01) == 1.0);
+  CHECK(Math::roundDown(1.995, 0.01) == 2.0);
+
+  CHECK(Math::roundUp(-1.0, 0.01) == -1.0);
+  CHECK(Math::roundDown(-1.0, 0.01) == -1.0);
+
+  CHECK(Math::roundUp(-1.99, 0.01) == -1.0);
+  CHECK(Math::roundDown(-1.01, 0.01) == -2.0);
+
+  CHECK(Math::roundUp(-1.995, 0.01) == -2.0);
+  CHECK(Math::roundDown(-1.005, 0.01) == -1.0);
+}