Fix incorrect sign in Quaternion#getEulerAnglesZYX

JOML-CI · Dec 28, 2022 · 10bb9ae · 10bb9ae
1 parent 03cbd5e
commit 10bb9ae
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Showing 4 changed files with 46 additions and 2 deletions.
diff --git a/src/main/java/org/joml/Quaterniond.java b/src/main/java/org/joml/Quaterniond.java
@@ -2847,7 +2847,7 @@ public Vector3d getEulerAnglesXYZ(Vector3d eulerAngles) {
     }
 
     public Vector3d getEulerAnglesZYX(Vector3d eulerAngles) {
-        eulerAngles.x = Math.atan2(y * z + w * x, 0.5 - x * x + y * y);
+        eulerAngles.x = Math.atan2(y * z + w * x, 0.5 - x * x - y * y);
         eulerAngles.y = Math.safeAsin(-2.0 * (x * z - w * y));
         eulerAngles.z = Math.atan2(x * y + w * z, 0.5 - y * y - z * z);
         return eulerAngles;

diff --git a/src/main/java/org/joml/Quaternionf.java b/src/main/java/org/joml/Quaternionf.java
@@ -1956,7 +1956,7 @@ public Vector3f getEulerAnglesXYZ(Vector3f eulerAngles) {
     }
 
     public Vector3f getEulerAnglesZYX(Vector3f eulerAngles) {
-        eulerAngles.x = Math.atan2(y * z + w * x, 0.5f - x * x + y * y);
+        eulerAngles.x = Math.atan2(y * z + w * x, 0.5f - x * x - y * y);
         eulerAngles.y = Math.safeAsin(-2.0f * (x * z - w * y));
         eulerAngles.z = Math.atan2(x * y + w * z, 0.5f - y * y - z * z);
         return eulerAngles;

diff --git a/src/test/java/org/joml/test/QuaternionDTest.java b/src/test/java/org/joml/test/QuaternionDTest.java
@@ -147,6 +147,28 @@ void testGetEulerAnglesXYZ() {
             throw new AssertionError();
     }
 
+    @Test
+    void testGetEulerAnglesZYX() {
+        Random rnd = new Random(1L);
+        int failure = 0;
+        int N = 30000;
+        for (int i = 0; i < N; i++) {
+            double x = (rnd.nextFloat() * 2.0 - 1.0) * Math.PI;
+            double y = (rnd.nextFloat() * 2.0 - 1.0) * Math.PI;
+            double z = (rnd.nextFloat() * 2.0 - 1.0) * Math.PI;
+            Quaterniond p = new Quaterniond().rotateZ(z).rotateY(y).rotateX(x);
+            Vector3d a = p.getEulerAnglesZYX(new Vector3d());
+            Quaterniond q = new Quaterniond().rotateZ(a.z).rotateY(a.y).rotateX(a.x);
+            Vector3d v = new Vector3d(rnd.nextFloat()*2-1, rnd.nextFloat()*2-1, rnd.nextFloat()*2-1);
+            Vector3d t1 = p.transform(v, new Vector3d());
+            Vector3d t2 = q.transform(v, new Vector3d());
+            if (!t1.equals(t2, 1E-10f))
+                failure++;
+        }
+        if ((float)failure / N > 0.0001f) // <- allow for a failure rate of 0.01%
+            throw new AssertionError();
+    }
+
     @Test
     void testGetEulerAnglesZXY() {
         Random rnd = new Random(1L);

diff --git a/src/test/java/org/joml/test/QuaternionfTest.java b/src/test/java/org/joml/test/QuaternionfTest.java
@@ -214,6 +214,28 @@ void testGetEulerAnglesXYZ() {
             throw new AssertionError();
     }
 
+    @Test
+    void testGetEulerAnglesZYX() {
+        Random rnd = new Random(1L);
+        int failure = 0;
+        int N = 30000;
+        for (int i = 0; i < N; i++) {
+            float x = (rnd.nextFloat() * 2f - 1f) * (float) Math.PI;
+            float y = (rnd.nextFloat() * 2f - 1f) * (float) Math.PI;
+            float z = (rnd.nextFloat() * 2f - 1f) * (float) Math.PI;
+            Quaternionf p = new Quaternionf().rotateZYX(z, y, x);
+            Vector3f a = p.getEulerAnglesZYX(new Vector3f());
+            Quaternionf q = new Quaternionf().rotateZ(a.z).rotateY(a.y).rotateX(a.x);
+            Vector3f v = new Vector3f(rnd.nextFloat()*2-1, rnd.nextFloat()*2-1, rnd.nextFloat()*2-1);
+            Vector3f t1 = p.transform(v, new Vector3f());
+            Vector3f t2 = q.transform(v, new Vector3f());
+            if (!t1.equals(t2, 1E-3f))
+                failure++;
+        }
+        if ((float)failure / N > 0.0001f) // <- allow for a failure rate of 0.01%
+            throw new AssertionError();
+    }
+
     @Test
     void testGetEulerAnglesZXY() {
         Random rnd = new Random(1L);