Tweaks/Tricks for solving low parralax footage reconstruction

[HaydenMartin]

I’m working with video footage to reconstruct part of a ruined section of an old abbey in England using Metashape. The first half of the clip has decent parallax, which allows Metashape to solve most of the reconstruction. However, the latter part transitions to nodal camera movement, with little to no parallax, making it difficult to reconstruct the topology accurately. I’ve managed to improve the results slightly by filtering the point cloud and culling images with poor matches or low projection accuracy. I’m looking for suggestions or Tweaks that could enhance the reconstruction, particularly for sections with low parallax.

[HaydenMartin]

man can someone just weigh in on this please? IDK if if been flagged or something for suggesting pretty relevant updates to the software on this forum or on facebook but even the most basic questions i'm asking just gather dust

[olihar]

Easy there...

You asked only few hours ago.

Photogrammetry is using Parallax, what do you want the software developers to do, create magic code?

EDIT: I had a quick look in general about your post history and questions, they are mostly asking for something very unordinary and misunderstanding of what Photogrammetry is.

[HaydenMartin]

olihar - i work in VFX and matchmoving - i know what photogrammetry is... We use the same SFM approach to match cameras in CGI to live action footage. The reason I use Metashape is because I can reconstruct a film location via the GPU which is much faster... Any questions that may seem unusual are from more of an R&D standpoint

As for my question, yeah it's quite urgent and I've been asking all around with no luck. I don't see any consolidated list of tweaks and their effects anywhere so it's a bit of a guessing game and I dont have the time for that. Tweaks have helped me a great deal in the past reconstructing tricky objects, so I'm hoping there's something out there to increase parallax sensitivity, because this footage is still handheld, so there will still be micro amounts of parallax even if it's a few centimeters offset here and there

[olihar]

Then you understand Photogrammetry needs parallax yet you demand photogrammetry without it.

[HaydenMartin]

"because this footage is still handheld, so there will still be micro amounts of parallax even if it's a few centimeters offset here and there"

to reiterate, I'm trying to find out if there's a way to increase the sensitivity to micro changes in parallax. It's not a demand, it's a fair question based on my understanding of Tweaks and how they can be used to drastically improve alignment and meshing when used correctly

[olihar]

Extremely small parallax is bad

[sylvaindemanet]

I don't know anything about your workflow but can you try to stabilize the handheld footage through a third party app to try and reduce the offsets. It'll probably crop the resolution...

[HaydenMartin]

Ah that’s an interesting approah! Thank you

 it would indeed crop the footage, but ultimately what’s most important is a decent mesh reconstruction - I can matchmove to the mesh to the footage afterwards

If I cropped and stabilized, I’m guessing I’d need to adjust my alignment settings to be adaptive?

[sylvaindemanet]

Here's what the manual says about adaptave camera fitting

Adaptive camera model fitting
This option enables automatic selection of camera parameters to be included into adjustment based on their reliability estimates. For data sets with strong camera geometry, like images of a building taken from all the sides around, including different levels, it helps to adjust more parameters during initial camera alignment. For data sets with weak camera geometry , like a typical aerial data set, it helps to prevent divergence of some parameters. For example, estimation of radial distortion parameters for data sets with only small central parts covered by the object is very unreliable. When the option is unchecked, Metashape will refine only the fixed set of parameters: focal length, principal point position, three radial distortion coefficients (K1, K2, K3) and two tangential distortion coefficients (P1, P2).

So I guess It wouldn't hurt selecting it.