Fix T75881: Animation, limitation of Bézier Handles

Relax limits of FCurve Bézier handles during evaluation. FCurve handles
can be scaled down to avoid the curve looping backward in time. This
scaling was done correctly but over-carefully, posing unnecessary
limitations on the possible slope of FCurves. This commit changes the
scaling approach such that the FCurve can become near-vertical.

Bump Blender's subversion from 291.0.1 to 291.0.2 to ensure that older
animation files are correctly updated.

Reviewed By: sybren

Differential Revision: https://developer.blender.org/D8752

tests/python/CMakeLists.txt

@@ -217,6 +217,15 @@ add_blender_test(
   --run-all-tests
 )
 
+# ------------------------------------------------------------------------------
+# ANIMATION TESTS
+add_blender_test(
+  bl_animation_fcurves
+  --python ${CMAKE_CURRENT_LIST_DIR}/bl_animation_fcurves.py
+  --
+  --testdir "${TEST_SRC_DIR}/animation"
+)
+
 # ------------------------------------------------------------------------------
 # IO TESTS
 

tests/python/bl_animation_fcurves.py

@@ -0,0 +1,92 @@
+# ##### BEGIN GPL LICENSE BLOCK #####
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software Foundation,
+#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ##### END GPL LICENSE BLOCK #####
+
+# <pep8 compliant>
+
+"""
+blender -b -noaudio --factory-startup --python tests/python/bl_animation_fcurves.py -- --testdir /path/to/lib/tests/animation
+"""
+
+import pathlib
+import sys
+import unittest
+
+import bpy
+
+class FCurveEvaluationTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.testdir = args.testdir
+      
+    def setUp(self):
+        self.assertTrue(self.testdir.exists(),
+                        'Test dir %s should exist' % self.testdir)
+
+    def test_fcurve_versioning_291(self):
+      # See D8752.
+      bpy.ops.wm.open_mainfile(filepath=str(self.testdir / "fcurve-versioning-291.blend"))
+      cube = bpy.data.objects['Cube']
+      fcurve = cube.animation_data.action.fcurves.find('location', index=0)
+
+      self.assertAlmostEqual(0.0, fcurve.evaluate(1))
+      self.assertAlmostEqual(0.019638698548078537, fcurve.evaluate(2))
+      self.assertAlmostEqual(0.0878235399723053, fcurve.evaluate(3))
+      self.assertAlmostEqual(0.21927043795585632, fcurve.evaluate(4))
+      self.assertAlmostEqual(0.41515052318573, fcurve.evaluate(5))
+      self.assertAlmostEqual(0.6332430243492126, fcurve.evaluate(6))
+      self.assertAlmostEqual(0.8106040954589844, fcurve.evaluate(7))
+      self.assertAlmostEqual(0.924369215965271, fcurve.evaluate(8))
+      self.assertAlmostEqual(0.9830065965652466, fcurve.evaluate(9))
+      self.assertAlmostEqual(1.0, fcurve.evaluate(10))
+
+    def test_fcurve_extreme_handles(self):
+      # See D8752.
+      bpy.ops.wm.open_mainfile(filepath=str(self.testdir / "fcurve-extreme-handles.blend"))
+      cube = bpy.data.objects['Cube']
+      fcurve = cube.animation_data.action.fcurves.find('location', index=0)
+
+      self.assertAlmostEqual(0.0, fcurve.evaluate(1))
+      self.assertAlmostEqual(0.004713400732725859, fcurve.evaluate(2))
+      self.assertAlmostEqual(0.022335870191454887, fcurve.evaluate(3))
+      self.assertAlmostEqual(0.06331237405538559, fcurve.evaluate(4))
+      self.assertAlmostEqual(0.16721539199352264, fcurve.evaluate(5))
+      self.assertAlmostEqual(0.8327845335006714, fcurve.evaluate(6))
+      self.assertAlmostEqual(0.9366875886917114, fcurve.evaluate(7))
+      self.assertAlmostEqual(0.9776642322540283, fcurve.evaluate(8))
+      self.assertAlmostEqual(0.9952865839004517, fcurve.evaluate(9))
+      self.assertAlmostEqual(1.0, fcurve.evaluate(10))
+
+
+def main():
+    global args
+    import argparse
+
+    if '--' in sys.argv:
+        argv = [sys.argv[0]] + sys.argv[sys.argv.index('--') + 1:]
+    else:
+        argv = sys.argv
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--testdir', required=True, type=pathlib.Path)
+    args, remaining = parser.parse_known_args(argv)
+
+    unittest.main(argv=remaining)
+
+
+if __name__ == "__main__":
+    main()