[gdal-dev] Converting OBJ to Geojson files with ogr2ogr

[Paul Harwood]

Whatever works for you - although I can sense the purists going cross-eyed
at the phrase "using Geojson as our internal coordinate system " :) I think
you might be piling up problems for your self later - but then I don't know
your scope.

Good luck.

PS - just to be clear "purist" is not meant to be in any way pejorative.

On Wed, 2 Dec 2020 at 20:57, Brandon Biggs <brandon.biggs at ski.org> wrote:

> Hello,
> We're using JavaScript, not Unity, but this is very interesting, I wish it
> was a JS package.
> We're kind of using Geojson as our internal coordinate system at the
> moment, but with a few oddities, like allowing 0.0 as the origin, rather
> than using Long lat.
> I just built a parser, so we're good.
> Thanks,
>
>
> Brandon Biggs <https://www.ski.org/users/brandon-biggs>
> Engineer
>
> Smith-Kettlewell Eye Research Institute
> Office: 415-345-2130
> Cell: 650-833-9394
>
> ------------------------------
> *From:* Paul Harwood <runette at gmail.com>
> *Sent:* Wednesday, December 2, 2020 12:20 PM
> *To:* Brandon Biggs <brandon.biggs at ski.org>
> *Cc:* Andrew C Aitchison <andrew at aitchison.me.uk>;
> gdal-dev at lists.osgeo.org <gdal-dev at lists.osgeo.org>
> *Subject:* Re: [gdal-dev] Converting OBJ to Geojson files with ogr2ogr
>
> GeoJSON is very good for many things but I would not convert an .OBJ to
> GeoJSON and then into the VR space local coordinate system. You are going
> to have project the OBJ into 4326 and then project it again into the local
> coordinate system - even if implicitly. Go directly from OBJ to an internal
> mesh.
>
> If you are building the VR in Unity - you can use this to do it :
>
> https://openupm.com/packages/com.virgis.geometry3sharp/
>
> You really should take a look at what we are doing at www.virgis.org - we
> have worked a lot of this out. It is in Unity but even if you are not using
> Unity there could be good learnings.
>
>
>
>
>
> On Wed, 2 Dec 2020 at 16:02, Brandon Biggs <brandon.biggs at ski.org> wrote:
>
> Hello,
> It's for a custom coordinate system for VR. Geojson provides a very easy
> syntax for properties and geometries that I like to use with origin at 0,0
> bottom left.
> I'll probably write my own converter, as OBJ is kind of an important file
> type we need to support.
> Thanks,
>
>
> Brandon Biggs <https://www.ski.org/users/brandon-biggs>
> Engineer
>
> Smith-Kettlewell Eye Research Institute
> Office: 415-345-2130
> Cell: 650-833-9394
>
> ------------------------------
> *From:* Paul Harwood <runette at gmail.com>
> *Sent:* Wednesday, December 2, 2020 2:31 AM
> *To:* Andrew C Aitchison <andrew at aitchison.me.uk>
> *Cc:* Brandon Biggs <brandon.biggs at ski.org>; gdal-dev at lists.osgeo.org <
> gdal-dev at lists.osgeo.org>
> *Subject:* Re: [gdal-dev] Converting OBJ to Geojson files with ogr2ogr
>
> .OBJ is a simple object mesh  (or to put it in more traditional terms:
> TIN) - it has shape but no data values and is not geolocated.
>
> I don't think there is any driver for OGR that will read .OBJ.
>
> You are going to problems with geolocation if you write your own. Geojson
> requires that the geometries are geolocated - and in the current version
> that they are in epsg:4326. That is not totally impossible - people have
> been using .dxf files for gis data for decades and that format is also not
> in theory geolocated. It is not a trivial problem though.
>
> I guess I would ask the usual question .. why?
>
> - what are you actually trying to achieve and why a GIS format like
> GeoJSON?
>
> - If you have to use GeoJSON - I am guessing you are transferring some
> data to something that reads GeoJSON only? In that case - can your source
> produce .dxf? OGR can read .dxf.
>
> - If you only have the source in .OBJ - what other formats can the
> destination read? Although, if you only have the source in .obj, I very
> much doubt any of the GIS tools like GDAL are going to be able to help you.
> It just is not a format used in GIS.
>
> It is a problem we solved in the ViRGiS projec <http://www.virgis.org>t -
> since .obj is used a lot in VR. There we used an existing library to read
> the .obj files - but that is in C# and I doubt that would help you.
>
> On Tue, 1 Dec 2020 at 20:15, Andrew C Aitchison <andrew at aitchison.me.uk>
> wrote:
>
> On Tue, 1 Dec 2020, Brandon Biggs wrote:
>
> > Hello,
> > I am wondering how to convert an obj file to a geojson file? I am using
> ogr2ogr with the command:
> > Ogr2ogr -f geojson output.geojson input.obj
> > But get the error that ogr2ogr does not have an OBJ driver. I looked on:
> > the vector drivers page<https://gdal.org/drivers/vector/index.html>
> > but am unable to find a simple obj converter. I am wondering if there is
> such a thing? I am probably going to write my own that does what I want,
> because OBJ is so simple, I was just wondering if GDAL could already do it.
>
> I've never heard of OBJ, but that doesn't mean much.
>
> If you only want a read-only ogr driver you might want to look at
>         https://gdal.org/tutorials/vector_python_driver.html
> if you would find a quick-n-dirty python quicker to write than C++.
>
> --
> Andrew C. Aitchison                                     Kendal, UK
>                         andrew at aitchison.me.uk
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>
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