This is a great and very valuable addition to FOSS. It makes it possible to do all sorts of editing and stabilization even with 3D 360 and 3D VR180 videos, just that it’s a bit slow of a workflow.
It would be awesome if you could modify this for stabilization of 3D VR180 or 3D 360, you’ve already done the hardest parts.
3D VR180 is basically 2 side-by-side halves of 2D 360 (the center parts of 2D 360 basically)
3D 360 is 2 instances of 2D 360 above each other, one on the top, one on the bottom.
The way I use your plugin to stabilize 3D VR180
I render each eye with ffmpeg as the center in 2D 360 video and then in Shotcut with your plugin, the back-facing track points have nothing to work with, it’s black there so they’re disabled but the one most center track point group works normally. The 2 track-point groups that are close to the center one would need to be even closer to the center to fit whithin 180 degrees but even so, they still work to improve the video stabilization.
For 3D 360 stabilization, again, I split the top and bottom videos into two 2D 360 videos with ffmpeg and then enter each one in Shotcut to stabilize it with your plugin
Then at the end I use whether Shotcut or ffmpeg to remerge the stabilized top and bottom into 3D 360. But all this requires multiple steps.
So what would be best for the plugin to do for 3D VR180 videos would be to treat each side-by-side half as the center half of a 2D 360 video, have the 3 track-point groups fit whithin 180 degrees to stabilize the center half of each resulting 2D 360 video and then maybe cut each center half of each of these stabilized 2D 360 videos and place them as the left and right half of 3D VR180 video.
Same for 3D 360 video: treat each half, the top and the bottom one as 2D 360, stabilize each and render them above each other, as in the original file.
You could make a lot of people’s lives easier, 3D VR180 and 3D 360 video stabilization software costs a lot of money otherwise, hundreds of dollars which is out of reach for many. What you did offering these 2D 360 plugins as FOSS is fantastic and these plugins complement Shotcut and ffmpeg which are also fantastic pieces of FOSS.