fix: set local.position only when repeat_primitive is False

When repeat_primitive=True, vertices are already translated in the buffer
by repeat_primitive(), so setting local.position would cause a double offset.
When repeat_primitive=False, raw vertices are not translated, so we need
local.position = centers[0] to place the object correctly.

Added tests for both cases in test_core.py.

Author: faris-agour

fury/actor/core.py

@@ -437,7 +437,8 @@ def actor_from_primitive(
         wireframe_thickness=wireframe_thickness,
     )
     obj = create_mesh(geometry=geo, material=mat)
-    
+    if not repeat_primitive:
+        obj.local.position = centers[0]
     obj.prim_count = prim_count
     return obj
 

fury/actor/tests/conftest.py

@@ -3,6 +3,7 @@
 import rendercanvas.glfw
 
 from fury import actor
+from fury.primitive import prim_sphere
 
 
 def _do_nothing_patch(self):
@@ -17,3 +18,9 @@ def sphere_actor():
     centers = np.array([[0.0, 0.0, 0.0]], dtype=np.float32)
     colors = np.array([[1.0, 0.0, 0.0]], dtype=np.float32)
     return actor.sphere(centers=centers, colors=colors)
+
+
+@pytest.fixture
+def sphere_prim():
+    vertices, faces = prim_sphere(phi=8, theta=8)
+    return vertices, faces

fury/actor/tests/test_core.py

@@ -4,6 +4,7 @@
 
 from fury import actor, geometry, material, window
 from fury.actor import Actor, Image as ActorImage, Text
+from fury.actor.core import actor_from_primitive
 from fury.actor.tests._helpers import validate_actors
 
 
@@ -188,3 +189,33 @@ def test_axes():
     assert 0 < mean_b < 255
 
     scene.remove(axes_actor)
+
+
+def test_actor_from_primitive_position_with_repeat(sphere_prim):
+    vertices, faces = sphere_prim
+    centers = np.array([[5, 10, 15]], dtype=np.float32)
+    colors = np.array([[1, 0, 0]])
+
+    obj = actor_from_primitive(
+        vertices, faces, centers, colors=colors, repeat_primitive=True
+    )
+
+    np.testing.assert_array_equal(
+        obj.local.position, np.array([0, 0, 0], dtype=np.float32)
+    )
+    mean_vertex = np.round(np.mean(obj.geometry.positions.data, axis=0))
+    np.testing.assert_array_almost_equal(mean_vertex, centers[0])
+
+
+def test_actor_from_primitive_position_without_repeat(sphere_prim):
+    vertices, faces = sphere_prim
+    centers = np.array([[5, 10, 15]], dtype=np.float32)
+    colors = np.array([[1, 0, 0]])
+
+    obj = actor_from_primitive(
+        vertices, faces, centers, colors=colors, repeat_primitive=False
+    )
+
+    np.testing.assert_array_equal(
+        obj.local.position, np.array([5, 10, 15], dtype=np.float32)
+    )