2D Motion vector from Houdini?



Hello !
Sorry if feels like double post, I longly hesitated to continue the motion vectors thread or start a new one, but since it’s quite houdini , I didn’t wanted to flood the other thread. :thinking:

SO ! since Houdini 16.5 release an intriguing feature has been included, Volume Optical Flow ! I didn’t see any talk or tutorial about it, maybe this is not reliable for game need ?

I tried to generate motion vector from a flipbook animation. I’m slowly getting there but my math skill and Houdini’s knowledge hitting a wall now.

I know they could be generated with the gamedev toolkit but I want to use 2d source for all my flipbook need , like more motion graphics stuff ect.

As you can see I’m almost there (kinda?), but few things are off, It seem my vectors are flipped somehow and don’t errr spread enough ?

Here’s my hip file, hope you don’t mind some of my math/logic foolishness.
Hip file

Thanks :slight_smile:

PS : As @Partikel mentioned below, I based my experiment on this great tutorial https://vimeo.com/242373845


Bare in mind, in Slate I’m doing other options too, so it’s difficult to aim for that as a ground-truth if you haven’t got those. FWIW you could get your houdini output, in Slate, with the correct settings. So I’d say you are pretty close. It kind of looks like a search distance setting, where the Houdini version is tighter in your example. If you can expand the search range you’d prob have quite similar.

It all comes down to preference as there’s not really a “correct” way to do them

Your vectors being flipped isn’t a big deal, it depends on the target.


Just adding in the Mark Fancher Tutorial for others to see. I’m guessing it’s what your stuff is based on. I think he does a good job of explainig the O flow node.


Indeed ! Forgot to add the reference, my bad.