Regard3D - Free, open source photogrammetry software

[Rob Martens]

I've hemmed and hawed for a few days about where exactly to post this, but finally decided to just make a dedicated thread and get it over with.

Regard3D[www.regard3d.org] is a free, open source photogrammetry tool available for Windows, OS X and Linux. I stumbled over it a few days back, and although I don't have any finished workshop content to show off just yet, I'm optimistic based on what I've seen from the software so far.

Regard is free for commercial work just as much as non-commercial, and patent free (to the best of the author's knowledge) since he's gone out of his way to avoid David Lowe's SIFT feature extraction algorithm, which many such programs use. OpenMVG, one of the base libraries Regard depends on, also uses it by default, but the developer stripped it out and implemented alternative solutions. Nonetheless, as is customary on the internet, I'll remind everyone that I am not a lawyer, so don't assume I know what I'm talking about regarding software patent law.

To use Regard, Windows and Mac users can download binaries from the project's site. If you're running Linux instead, I'm sorry to say you'll have to build from source. There's a Github repo[github.com] for the code, and build instructions are on the project's website[www.regard3d.org].

Once you have a copy of the software itself, you'll then need a camera sensor size database to go with it. OpenMVG provides one, so I'm not sure why a copy isn't shipped with Regard by default, but you can grab it from its own Github repository[github.com] easily enough. You'll want to put sensor_database.csv in the main Regard3D directory, alongside the main executable. Once that's in place, the program should launch without complaining, and you can start with the tutorial[www.regard3d.org].

If your camera's not in the database, you can add it yourself; research your camera's sensor size online, and find either the exact dimensions in millimeters, or the 1/x.y" spec which you can get real measurements out of using this chart[en.wikipedia.org]. Find the width (not diagonal) and add your camera to the database following the format you see for the other entries.

I have hope that sooner or later I'll be able to put together a guide or at least sample Destination using Regard3D that I can share, but in the meantime I thought at least a few people would find this software as interesting as I did.

[Ṭoyoka]

I'm happy to see a free alternative to what we currently have (the demos of our current choices are sort of limited). Hoping for a tutorial some time in the near future, thanks for this!

[Cargo Cult]

I haven't had a chance to try out Regard3D yet, but it sounds really interesting - do feel free to add any useful information about relevant tools and workflow details to the Destinations wiki!

[Rob Martens]

I was considering doing just that, initially, but I wasn't sure exactly how to go about it. I'm familiar with basic wiki operation, at least, and it will be easy enough to tack Regard3D onto the bottom of the existing list of software.

The "workflow details" you mentioned are where I get stuck, however. What would be the best way to add those? I wouldn't want to clutter up the "Creating a Destination" page, since it's focused on RealityCapture, so that leaves the options of making a new wiki page and linking to it, or making a Steam guide and linking to that instead. Is there an approach you'd prefer users go with when adding information like this?

[Cargo Cult]

Creating a new wiki page should be fine - everything is super-malleable, so go with whichever seems most convenient.

[Rob Martens]

It took a few days to get a handle on what I was doing (my usual point and shoot camera dying in the middle of the process didn't help), but I've finished a basic introduction to Regard3D. If anyone has questions about the tutorial or software, I'll try my best to help! No promises, though, I'm only just getting started with all this.

Sorry about the lack of pictures on that page, by the way. I have a functioning account on the wiki, and I confirmed my email address a few days ago, so I'm not sure why I can't upload files. If anyone knows what I have to do to get in the "autoconfirmed users" group, I'd love to know so I can upload these screenshots I'm so proud of.

[Ṭoyoka]

Thanks for the fabulously detailed tutorial! This is a great resource :)

[R-S]

Unfortunately it dosn't work with the Microsoft Lumia 950 XL. I think it's because in the EXIF of the photos - there is no "Focal length" written. And Regard3D can't process the photos without "Focal length"...

[Rob Martens]

Ah, sorry, I'll need to add a note about that. You're right, you need to know the focal length in order for the software to work. If you were able to somehow determine the focal length of each photo, you could technically edit the XML-based .r3d project file and add it manually (look for the <focalLength> tag for each picture), but Regard can't otherwise process the images. Sorry I didn't point that out! Maybe Microsoft will release a firmware update one day that records focal length?

[R-S]

Many thanks! Editing the .r3d project file works fine :)
Right, normally Microsoft has to release a firmware/software update for this...

[Rob Martens]

Oh god, one more stupid mistake! I should have pointed out it's the actual focal length you need, not the 35mm equivalent. All I can find for the Lumia 950 XL is 26mm; that's greater than the thickness of the phone itself, so we can assume it's the "35mm equivalent" measurement, not the real focal length. It also doesn't tell you what focal length was used for zoomed in shots. I suspect you'll end up with strange results, if any at all. Sorry for not mentioning that!

[R-S]

Yeah no problem :) the strage result is that windows says: "Regard3D app has stopped working..." :-) I don't use zoomed in shots, so is there a change to calculate the real focal length from the "35mm equivalent" measurement (26mm)?

[Rob Martens]

I thought about that before I replied to you, but wasn't sure if it was possible. A bit more research, though, and I now think you might be able to do it, or at least get close.

First calculate the crop factor of your sensor, basically the ratio between your camera's sensor size and the sensor size of 35mm film; that's 36x24mm, so the diagonal is roughly 43.2666mm.

Your phone uses a 1/2.4" type sensor, which according to the detailed version of the openMVG sensor database[github.com] is roughly 5.9x4.43mm, with a diagonal of about 7.378mm. 43.2666 / 7.378 = ~5.8643.

Then just divide the 35mm equivalent focal length by the crop factor, 26 / 5.8643, and get a resulting actual focal length of roughly 4.4336mm.

This is all very rough, and I'm no engineer or scholar of optics, so the measurements could be off, or for that matter the entire premise could be faulty. Doing the math on the numbers for my Cybershot T500, where I know all the values, shows that it works out to be in the ballpark of the right answer. I can't say I know whether there's such a thing as "close enough" when it comes to Regard3D's calculations, but with a substantial amount of luck my math will give you a focal length that the software can do something with.

I make no guarantees, though, so please don't get your hopes up.

[R-S]

Cool, thank you very much! :) I will try that tomorrow with 4.4336mm. No problem when it don't work.. ;-)

[R-S]

hmm it don't work, but it's maybe some other problem.

[QuickNinjaCat]

FYI:
I added a link to the Regard3D article/page to the Destinations hub page on the VDC Wiki, since it wasn't there originally.