javadoc and comments

src/main/java/com/github/stephengold/joltjni/Quat.java

@@ -167,8 +167,9 @@ public void set(QuatArg source) {
     }
 
     /**
-     * Create a rotation quaternion from Euler angles. Rotation order is X then
-     * Y then Z.
+     * Create a rotation quaternion from the specified Tait-Bryan angles,
+     * applying the rotations in x-y-z extrinsic order or z-y'-x" intrinsic
+     * order.
      *
      * @param angles the desired rotation around each axis (in radians, not
      * null, unaffected)

src/main/java/com/github/stephengold/joltjni/operator/Op.java

@@ -573,13 +573,13 @@ public static Vec3 star(QuatArg left, Vec3Arg right) {
         float ry = right.getY();
         float rz = right.getZ();
 
-        // a = lhs x pure(rhs)
+        // a = left x pure(right)
         float aw = -lx * rx - ly * ry - lz * rz;
         float ax = lw * rx + ly * rz - lz * ry;
         float ay = lw * ry - lx * rz + lz * rx;
         float az = lw * rz + lx * ry - ly * rx;
 
-        // result = vec3(a x conjugate(lhs))
+        // result = vec3(a x conjugate(left))
         float x = -aw * lx + ax * lw - ay * lz + az * ly;
         float y = -aw * ly + ax * lz + ay * lw - az * lx;
         float z = -aw * lz - ax * ly + ay * lx + az * lw;

src/main/java/com/github/stephengold/joltjni/readonly/QuatArg.java

@@ -102,7 +102,7 @@ public interface QuatArg {
     /**
      * Test whether the quaternion is zero. The quaternion is unaffected.
      *
-     * @return {@code true} if zero, otherwise {@code false}
+     * @return {@code true} if exactly zero, otherwise {@code false}
      */
     boolean isZero();