Anim: Add regression tests for NLA strip evaluation

Adding in regression tests for NLA strip evaluation

Co-authored-by: Paolo Amadini <paolo.blender.dev@amadzone.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/109212

tests/python/CMakeLists.txt

@@ -393,6 +393,11 @@ add_blender_test(
   --testdir "${TEST_SRC_DIR}/animation"
 )
 
+add_blender_test(
+  bl_animation_nla_strip
+  --python ${CMAKE_CURRENT_LIST_DIR}/bl_animation_nla_strip.py
+)
+
 add_blender_test(
   bl_rigging_symmetrize
   --python ${CMAKE_CURRENT_LIST_DIR}/bl_rigging_symmetrize.py

tests/python/bl_animation_nla_strip.py

@@ -0,0 +1,121 @@
+# SPDX-FileCopyrightText: 2023 Blender Authors
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+"""
+Tests the evaluation of NLA strips based on their properties and placement on NLA tracks.
+"""
+
+import bpy
+import sys
+import unittest
+
+
+class AbstractNlaStripTest(unittest.TestCase):
+    """ Sets up a series of strips in one NLA track. """
+
+    test_object: bpy.types.Object = None
+    """ Object whose X Location is animated to check strip evaluation. """
+
+    nla_tracks: bpy.types.NlaTracks = None
+    """ NLA tracks of the test object, which are cleared after each test case. """
+
+    action: bpy.types.Action = None
+    """ Action with X Location keyed on frames 1 to 4 with the same value as the frame, with constant interpolation. """
+
+    @classmethod
+    def setUpClass(cls):
+        bpy.ops.wm.read_factory_settings(use_empty=True)
+
+        cls.test_object = bpy.data.objects.new(name="Object", object_data=bpy.data.meshes.new("Mesh"))
+        bpy.context.collection.objects.link(cls.test_object)
+        cls.test_object.animation_data_create()
+
+        cls.nla_tracks = cls.test_object.animation_data.nla_tracks
+
+        cls.action = bpy.data.actions.new(name="ObjectAction")
+        x_location_fcurve = cls.action.fcurves.new(data_path="location", index=0, action_group="Object Transforms")
+        for frame in range(1, 5):
+            x_location_fcurve.keyframe_points.insert(frame, value=frame).interpolation = "CONSTANT"
+
+    def tearDown(self):
+        while len(self.nla_tracks):
+            self.nla_tracks.remove(self.nla_tracks[0])
+
+    def add_strip_no_extrapolation(self, nla_track: bpy.types.NlaTrack, start: int) -> bpy.types.NlaStrip:
+        """ Places a new strip with the test action on the given track, setting extrapolation to nothing. """
+        strip = nla_track.strips.new("ObjectAction", start, self.action)
+        strip.extrapolation = "NOTHING"
+        return strip
+
+    def assertFrameValue(self, frame: float, expected_value: float):
+        """ Checks the evaluated X Location at the given frame. """
+        int_frame, subframe = divmod(frame, 1)
+        bpy.context.scene.frame_set(frame=int(int_frame), subframe=subframe)
+        self.assertEqual(expected_value, self.test_object.evaluated_get(
+            bpy.context.evaluated_depsgraph_get()
+        ).matrix_world.translation[0])
+
+
+class NlaStripSingleTest(AbstractNlaStripTest):
+    """ Tests the inner values as well as the boundaries of one strip on one track. """
+
+    def test_extrapolation_nothing(self):
+        """ Tests one strip with no extrapolation. """
+        self.add_strip_no_extrapolation(self.nla_tracks.new(), 1)
+
+        self.assertFrameValue(0.9, 0.0)
+        self.assertFrameValue(1.0, 1.0)
+        self.assertFrameValue(1.1, 1.0)
+        self.assertFrameValue(3.9, 3.0)
+        self.assertFrameValue(4.0, 4.0)
+        self.assertFrameValue(4.1, 0.0)
+
+
+class NlaStripBoundaryTest(AbstractNlaStripTest):
+    """ Tests two strips, the second one starting when the first one ends. """
+
+    # Incorrectly, the first strip is currently evaluated at the boundary between two adjacent strips (see #113487).
+    @unittest.expectedFailure
+    def test_adjacent(self):
+        """ The second strip should be evaluated at the boundary between two adjacent strips. """
+        nla_track = self.nla_tracks.new()
+        self.add_strip_no_extrapolation(nla_track, 1)
+        self.add_strip_no_extrapolation(nla_track, 4)
+
+        self.assertFrameValue(3.9, 3.0)
+        self.assertFrameValue(4.0, 1.0)
+        self.assertFrameValue(4.1, 1.0)
+
+    def test_adjacent_muted(self):
+        """ The first strip should be evaluated at the boundary if it is adjacent to a muted strip. """
+        nla_track = self.nla_tracks.new()
+        self.add_strip_no_extrapolation(nla_track, 1)
+        self.add_strip_no_extrapolation(nla_track, 4).mute = True
+
+        self.assertFrameValue(3.9, 3.0)
+        self.assertFrameValue(4.0, 4.0)
+        self.assertFrameValue(4.1, 0.0)
+
+    def test_first_above_second(self):
+        """ The first strip should be evaluated at the boundary, when followed by another strip on a track below. """
+        self.add_strip_no_extrapolation(self.nla_tracks.new(), 4)
+        self.add_strip_no_extrapolation(self.nla_tracks.new(), 1)
+
+        self.assertFrameValue(3.9, 3.0)
+        self.assertFrameValue(4.0, 4.0)
+        self.assertFrameValue(4.1, 1.0)
+
+    def test_second_above_first(self):
+        """ The second strip should be evaluated at the boundary, when preceded by another strip on a track below. """
+        self.add_strip_no_extrapolation(self.nla_tracks.new(), 1)
+        self.add_strip_no_extrapolation(self.nla_tracks.new(), 4)
+
+        self.assertFrameValue(3.9, 3.0)
+        self.assertFrameValue(4.0, 1.0)
+        self.assertFrameValue(4.1, 1.0)
+
+
+if __name__ == "__main__":
+    # Drop all arguments before "--", or everything if the delimiter is absent. Keep the executable path.
+    unittest.main(argv=sys.argv[:1] + (sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []))