io_scene_fbx/import_fbx.py

@@ -575,9 +575,24 @@ def blen_read_animations_action_item(action, item, cnodes, fps, anim_offset, glo
     from itertools import chain
 
     fbx_curves = []
+    used_channels = set()
+    warn_multiple_curves_per_channel = False
     for curves, fbxprop in cnodes.values():
         for (fbx_acdata, _blen_data), channel in curves.values():
-            fbx_curves.append((fbxprop, channel, fbx_acdata))
+            channel_id = (fbxprop, channel)
+            if channel_id in used_channels:
+                # The FBX animation system's default implementation only uses the first curve assigned to a channel.
+                # Additional curves per channel are allowed by the FBX specification, but the handling of these curves
+                # is considered the responsibility of the application that created them. Note that each curve node is
+                # expected to have a unique set of channels, so these additional curves with the same channel would have
+                # to belong to separate curve nodes. See the FBX SDK documentation for FbxAnimCurveNode.
+                warn_multiple_curves_per_channel = True
+            else:
+                used_channels.add(channel_id)
+                fbx_curves.append((fbxprop, channel, fbx_acdata))
+    if warn_multiple_curves_per_channel:
+        print("WARNING: Multiple animation curves per animated property channel were found for %s. All but the first"
+              "curve for each property channel has been discarded." % action.name)
 
     # Leave if no curves are attached (if a blender curve is attached to scale but without keys it defaults to 0).
     if len(fbx_curves) == 0: