Armature is deforming incorrectly when exported

I have a simple mesh with a simple rig. It animates fine within Blender, but when I export it to Blend4Web it stretches in an unpredictable and awkward way.

Here is what it looks like in Blender:


Here is what is happening in Blend4Web:


b4w_armature_deform.blend

Can someone please tell me what I've done wrong? Thanks.

Hi!

This kind of sophisticated animation requires baking. See the following topic in documentation to find out how.

Thank you Alexander! I've got it working now!

Result: b4w_armature_deform_b4wbaked.blend

I don't know if this is worth mentioning or not, but I initially got this error when I clicked the Bake button:

Traceback (most recent call last):
  File "/Users/user/blend4web_sdk_free/addons/blend4web/anim_baker.py", line 90, in execute
    self.process_action(action, armobj)
  File "/Users/user/blend4web_sdk_free/addons/blend4web/anim_baker.py", line 207, in process_action
    armobj.animation_data.action = action
AttributeError: bpy_struct: attribute "action" from "AnimData" is read-only

location: <unknown location>:-1

I think this is because I downloaded the .blend file from this post onto a different computer than the one it was created on, and had a file permissions problem. I was able to resolve this by looking at the file info and granting Read & Write permission to all users. I don't know if this will help anyone having a similar issue, but just in case…



One thing I am curious about: The option to Use Blender's Native Baker… for what kinds of animations would it be better to use the native baker instead of the B4W one? Or should I just always try the B4W one first and only resort to the native one as a fallback if I have a problem?
Thanks