glTF exporter: Keep CONSTANT/STEP animation when sample animations (object only for now, not bones)

1 files changed, 14 insertions, 1 deletions

diff --git a/io_scene_gltf2/blender/exp/gltf2_blender_gather_animation_samplers.py b/io_scene_gltf2/blender/exp/gltf2_blender_gather_animation_samplers.py
index 4b1ebeb1..27750a72 100755
--- a/io_scene_gltf2/blender/exp/gltf2_blender_gather_animation_samplers.py
+++ b/io_scene_gltf2/blender/exp/gltf2_blender_gather_animation_samplers.py
@@ -257,16 +257,29 @@ def __gather_interpolation(channels: typing.Tuple[bpy.types.FCurve],
                            bake_bone: typing.Union[str, None],
                            bake_channel: typing.Union[str, None]
                            ) -> str:
+
     # Note: channels has some None items only for SK if some SK are not animated
+
     if gltf2_blender_gather_animation_sampler_keyframes.needs_baking(blender_object_if_armature,
                                                                      channels,
                                                                      export_settings):
         if bake_bone is not None:
+            # TODO: check if the bone was animated with CONSTANT
             return 'LINEAR'
         else:
             max_keyframes = max([len(ch.keyframe_points) for ch in channels if ch is not None])
             # If only single keyframe revert to STEP
-            return 'STEP' if max_keyframes < 2 else 'LINEAR'
+            if max_keyframes < 2:
+                return 'STEP'
+            else:
+                blender_keyframe = [c for c in channels if c is not None][0].keyframe_points[0]
+
+                # For sampled animations: CONSTANT are STEP, other are LINEAR
+                return {
+                    "BEZIER": "LINEAR",
+                    "LINEAR": "LINEAR",
+                    "CONSTANT": "STEP"
+                }[blender_keyframe.interpolation]
 
     blender_keyframe = [c for c in channels if c is not None][0].keyframe_points[0]