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Jack Hubler-Dayton

3D File Formats to Archive and Display

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Hello All,

DNGs are the standard for archiving photos for posterity, my question is what is the best 3D file format? OBJ? 

I have noticed that STL and OBJ seem the most common to export from photoscan especially for CRM professionals however I find that those formats are not the easiest to share/display, especially loading online. I have used three.js in the past to display models and those developers recommend using gLTF format because of its quick load time and efficiency, hence the nickname "jpeg of 3d". Any thoughts here? PDF's are easy to share but I know they are a horribly lossy file format...

P.S.

On this form I found a OBJ/Collada>gLTF converter

 https://groups.google.com/forum/#!topic/cesium-dev/0tzql9s-e6M . 

 

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Jack,

I think this is an important question to consider, and the answer may depend on the purpose and the longevity expected. You mention Archive and Display, and I think there are useful parallels in terms of images, especially as we may have one format for long-term assured storage and another for speedier manipulation and display.

 

You mention DNG, and DNG can contain TIFFs. Top-level archives which accept images will often specify they must be un-compressed TIFFs. This seems counter-intuitive in that they are taking on storage obligations which could be significantly reduced, but they are protecting against future licensing changes. The TIFF standard has no proprietary issues, but some of the algorithms behind compression standards, whilst open to read and implement at present, are private property, and there is the danger that permission may be revoked.

 

Whilst not implying any concerns over or criticism of Khronos, it states at the top of https://www.khronos.org/gltf/ “glTF™ (GL Transmission Format) is a royalty-free specification” – in other words, it looks to be remaining Khronos’s property.

 

There are precedents to be a little concerned, especially for the long-term. The Graphics Interchange Format (‘GIF’) is now thought of by most as a container for handy little images or animations etc. The GIF was developed by the Compuserve BBS team, and internally the data is losslessly compressed using LZW. LZW is proprietary, and from what I recall, there were attempts by those who owned them to assert their rights the LZW algorithm, and this led to the development of the open PNG standard.

 

I don’t have an answer in the ‘model archiving’ space but will be interested to learn.

 

Dave

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Great question Jack!

First, we think collecting high quality image sets with proper overlap and good geometry is the most critical thing. If you have that and you archive the images (preferably DNGs but could be TIFFs) along with good metadata about your project, you have something really useful for the future.  If you want to include models, we would recommend the OBJ or PLY formats.  We also recommend exporting masks and camera calibration data if possible.  These could be useful in better understanding your outputs.  Masks especially can take a lot of work and you don't want to lose that.  Software like Metashape (AKA PhotoScan) can easily export these things.  Other software may or may not be able to do this.

As part of our Digital Lab Notebook tools we have been working on some recommendations for archiving. This is still an early draft and we are getting some feedback from some advisors - so stay tuned.

Carla

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Great information, thank you for your responses Dave and Carla! I would absolutely like to avoid any potential issues with proprietary formats so it looks like I will continue using DNG and OBJ for archival purposes. Incorporating the Lab Notebook into my capture workflow during my next photogrammetry project is definitely on my list. I'm restoring a historic homestead fieldstone fence in Kansas right now and making a model of before and after should provide a good chance to gain a little familiarity with the Lab Notebook. 

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