Help stitching from camera rig

[Poul Jensen]

Hello,

I've built a camera rig for 4 full frame cameras with Sigma 15mm diagonal fisheyes - see photo included in zip-file linked below. One camera is vertical, the 3 others at 120 degree intervals horizontally and 70 degrees from vertical. This provides sufficient overlap for stitching, capturing everything down to about 20 degrees below the horizon. It obviously suffers from significant parallax, but when put in an open space it should be possible to get a good stitch, using control points on far subjects only.

The test shot I have been able to make for now (see images and PTGui project in zip-file) suffers from several issues, but nevertheless I was surprised to find that:
1) PTGui could generate no control points at all
2) Even with manual control points (only on far subjects) linking all images, the stitch is in PTGui's own words "very bad".

I am hoping someone with more experience with PTGui will care to take a look at the project file and perhaps identify how to get a decent stitch - or, if it's plain impossible, explain why PTGui is unable to make a good stitch. I tried setting yaw/pitch/roll for each image manually, but it seems lens distortion correction is not applied correctly without running the optimizer. Perhaps because the distortion coefficients a, b and c under lens correction default to zero? I do have an accurate lens mapping function (polar angle theta -> normalized radius, 5th order polynomial), but not sure how to derive the distortion coefficients (tried with AI, but the derived values completely messed up stitching).

Here's a link to the project file and (flawed) test images:
PTGui-4-camera-rig.zip

Thank you,
Poul Jensen

[PTGui Support]

Hi Poul,

I got a much better result by enabling 'individual lens parameters' for
all lenses, and optimizing the lens parameters. In your original project
the lens parameters were not optimized.

I also deleted 3 control points which had a very large distance,
probably they were misplaced.

Project file is attached.

You can even improve it further by enabling viewpoint optimization for
all images except one, this compensates for some of the parallax.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

> PTGui-4-camera-rig.zip <https://ktisisimiut-my.sharepoint.com/:u:/g/
> personal/pofl_kti_gl/IQBfIrGf9WP3QIiy5x9pNTHZAVQDnscWU325b-Lygrr2hvY?
> e=tdE7em>
>
> Thank you,
> Poul Jensen
>
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