Add zenith range to spherical volume and add tests

km3buu/geometry.py

@@ -186,13 +186,17 @@ class SphericalVolume(DetectorVolume):
     center: tuple [m]
         Coordinate center of the sphere
         (x, y, z)
+    zenith: float [1] (default (-1.0, 1.0)
+        Zenith range given as cos(θ)
     """
-    def __init__(self, radius, coord_origin=(0, 0, 0)):
+    def __init__(self, radius, coord_origin=(0, 0, 0), zenith=(-1, 1)):
         super().__init__()
         self._radius = radius
         self._coord_origin = coord_origin
         self._volume = self._calc_volume()
-        self._solid_angle = 4 * np.pi
+        self._cosZmin = zenith[0]
+        self._cosZmax = zenith[1]
+        self._solid_angle = 2 * np.pi * (self._cosZmax - self._cosZmin)
 
     def _calc_volume(self):
         return 4 / 3 * np.pi * np.power(self._radius, 3)
@@ -209,7 +213,7 @@ class SphericalVolume(DetectorVolume):
 
     def random_dir(self):
         phi = np.random.uniform(0, 2 * np.pi)
-        cos_theta = np.random.uniform(-1, 1)
+        cos_theta = np.random.uniform(self._cosZmin, self._cosZmax)
         return (phi, cos_theta)
 
     def header_entries(self, nevents=0):

km3buu/tests/test_geometry.py

@@ -42,6 +42,19 @@ class TestSphere(unittest.TestCase):
             radius = np.sqrt(np.sum(np.power((np.array(pos) - 2), 2)))
             assert radius <= 20
 
+    def test_limited_zenith(self):
+        np.random.seed(1234)
+        geometry = CanVolume(zenith=(-0.4, 0.5))
+        self.assertAlmostEqual(geometry.solid_angle, 5.654866776461628)
+        direction = geometry.random_dir()
+        self.assertAlmostEqual(direction[1], 0.15989789393584863)
+        geometry = CanVolume(zenith=(0.1, 0.3))
+        direction = geometry.random_dir()
+        self.assertAlmostEqual(direction[1], 0.25707171674275386)
+        geometry = CanVolume(zenith=(-0.3, -0.2))
+        direction = geometry.random_dir()
+        self.assertAlmostEqual(direction[1], -0.2727407394717358)
+
 
 class TestCan(unittest.TestCase):
     def setUp(self):
@@ -69,6 +82,7 @@ class TestCan(unittest.TestCase):
     def test_limited_zenith(self):
         np.random.seed(1234)
         geometry = CanVolume(zenith=(-0.4, 0.5))
+        self.assertAlmostEqual(geometry.solid_angle, 5.654866776461628)
         direction = geometry.random_dir()
         self.assertAlmostEqual(direction[1], 0.15989789393584863)
         geometry = CanVolume(zenith=(0.1, 0.3))