mattjakob Posted March 14, 2017 Share Posted March 14, 2017 (edited) Hello, I was wondering if it's possible to create velocity vectors from an animated sequence (texture). Ideally something similar to Optical Flow. I can extract movement from geometry (eg. use trail to generate v vector of animated VOP) and I can do basic image analysis (eg. convolution kernel operations on coloured points using VOP) so I feel it could be kind of possible to do it but can't get my head around it. In terms of results I'd like to create a particle system that reacts to an animated texture (eg. overlay particles on a animated texture and have them follow the movements in the video) thanks! Edited March 14, 2017 by mattjakob Quote Link to comment Share on other sites More sharing options...
mestela Posted March 16, 2017 Share Posted March 16, 2017 AFAIK people generate vectors in external apps (usually After Effects or Nuke with plugins like Twixor or go fancy with openCV libs or hacked ffmpeg builds), and then use that image sequence to make a velocity field. I assume that's how the amazing video below was done. (edit) Ah, he says in another video he uses deep flow: https://thoth.inrialpes.fr/src/deepflow/ (/edit) Had a quick look around last night and this morning, found this javascript image processing library. They have an implementation of 'Lucas-Kanade optical flow', I have a suspicion it'd be good starting point to port to vex: https://github.com/inspirit/jsfeat https://github.com/inspirit/jsfeat/blob/master/src/jsfeat_optical_flow_lk.js -matt 4 Quote Link to comment Share on other sites More sharing options...
petz Posted March 19, 2017 Share Posted March 19, 2017 On 16.3.2017 at 1:10 AM, mestela said: Had a quick look around last night and this morning, found this javascript image processing library. They have an implementation of 'Lucas-Kanade optical flow', I have a suspicion it'd be good starting point to port to vex: i don´t think this would be possible to implement as long as vex doesn´t support arbitrary sized matrices. on the other hand, it wouldn´t be much of a problem in python/numpy for which several implementations already exist. performance might be an issue, though ... Quote Link to comment Share on other sites More sharing options...
caskal Posted March 24, 2017 Share Posted March 24, 2017 Will love to know more about this stuff, been reading a lot and its driving me crazy. So far I created a motion vector with Twixtor Pro and imported to houdini, used the Cd to drive the velocity in pop, got some particles following the movement but not nearly close to that awesome video Quote Link to comment Share on other sites More sharing options...
Matsidefx Posted March 24, 2017 Share Posted March 24, 2017 Hello, Can you explain your work ?? Thanks to share Quote Link to comment Share on other sites More sharing options...
caskal Posted March 25, 2017 Share Posted March 25, 2017 17 hours ago, Matsidefx said: Hello, Can you explain your work ?? Thanks to share Hey Mat, I created a motion vector with twixtor pro, here's a tutorial ( ) Wich get me something like the top image here Then I modified to get sharper colors like the bottom one, and imported that sequence to a grid with attrib from map. Used that to drive the vel of a pop network, is not a good result but I think may be a starting point Cheers Quote Link to comment Share on other sites More sharing options...
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