Bake animation doesn't work with vertex animation?

[AllenDang]

I'm trying to export a simple animation “Growing line” into Unity.

The animation is very simple as below:

Curve I Carve <- Key frame the second U here. I Wireframe

I hit “Bake animation” button in Unity, a message box popup “No animation was found to bake”.

I'm using Houdini 16.0.621.

[SeelanV]

See https://www.sidefx.com/forum/topic/50604/