Archaeoastronomy in Stellarium

[Antwane Lee]

Hello:

I am new to Stellarium and am looking for reference materials for doing 3D simulations of  ancient sites in the software to better understand the astronomical alignments with architectural elements. I am a trained architect. Please see the link below to a YouTube video that shows how Stellarium can be used in this application:

https://www.youtube.com/watch?v=7QdENQLx8FE&t=100s

Please review and give me your thoughts on documents I can obtain and ways to do this.

Thank you.

Antwane

[Georg Zotti]

Thanks for your interest. Seems you found my talk already...

On stellarium.org you find a few recent papers linked. The JSA paper contains a lot of references to other relevant papers.

The User Guide, chapter 15, contains most relevant information on how to bring your georeferenced OBJ into Stellarium. Usually, if it looks OK in MeshLab, it should work in Stellarium. 

If static architecture is not enough, I have also developed a Unity module to use Stellarium's sky as background for a Unity-based simulation. See our github repo.

I am also available for (funded) collaboration... ;-) -- pm me!

Kind regards,

Georg

[Antwane Lee]

Georg:

I will take a look at the documentation and let you know if I have any questions.

Thank you for your assistance.

Antwane

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[Antwane Lee]

Georg:

I hope that you are doing well today.

I am still having issues understanding how to bring an OBJ file into Stellarium. Chapter 15 is not clear to me and appears to me more about how to export an OBJ file from other software packages.

Can you please send me links to video tutorials on the subject?

Please let me know.

Thanks again for your assistance.

Antwane

[Georg Zotti]

Please inspect the two examples that are included, Testscene or Sterngarten, or inspect the scenes available for download from Stellarium.org. I expect some knowledge about 3D model formats, and expect you to know about the difference between geographical coordinates and survey grid coordinates. 3D models are usually modelled in linear Cartesian coordinates. When the grid axes are parallel to a survey grid, files are easily imported.

I don't teach 3D modelling, and I am not aware of a video tutorial about how to exchange a few lines in a config file that uses English terminology and is fully described in the User Guide.

What data do you have?

[Kamil Lipek]

Is there an option to view the system and the earth live, in real time fps?

pt., 7.03.2025, 03:35 użytkownik Kamil Lipek <lipe...@gmail.com> napisał:

Is there an option in View, Polls, Deep Sky. Can I add a Select All button?

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[Kamil Lipek]

Is there an option in View, Polls, Deep Sky. Can I add a Select All button?

czw., 6.03.2025, 22:49 użytkownik Georg Zotti <georg...@univie.ac.at> napisał:

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[Kamil Lipek]

You can help me set up sandbox.game and PayPal developer

[Antwane Lee]

Georg:

I am an architect and have created a 3D model file that was exported from an Autocad file into OBJ format. My problem is that I cannot find instructions on how to bring my 3D model into Stellarium so I can see the astronomical alignments. I have the surrounding desert and mountains modelled in 3D based upon GIS data. Is there a way I can bring my model into Stellarium?

Please let me know.

Thanks again for your assistance.

Antwane

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[Georg Zotti]

I don't know what your problem is when all you write is "it does not work" and/or "I am clueless". The written instructions in the User Guide, all three pages of 15.4.3, are all that I can offer, and I refer to my own instructions myself whenever I need them.

Let us take for granted the OBJ has been exported as text file in the Wavefront OBJ format. Next to it is most likely a material file, .MTL. This is another text file which may point to textures. Many OBJ exporters mess up path names or material property keys. Check that the OBJ loads in MeshLab.

As written in the User Guide: In your Stellarium User Data Directory, locate or create a scenery3d subfolder. In that, create another subfolder for your model. Let's call it myModel. 

In scenery3d/myModel, add the OBJ, MTL and texture files (these can go into a subfolder, let us call it textures). The texture entries in the MTL file must point to the textures in the textures subfolder. Check that the OBJ loads in MeshLab.

In scenery3d/myModel, add a file scenery3d.ini. Make sure its ending is ini, not ini.txt. Windows is stupid to hide file endings by default.

Read the description of the scenery3d.ini file in the User Guide, and study the contents of the existing examples that have been set up like tutorials. Write keys exactly as shown, and values are they fit your data. What else shall I say at this point?

Then, tell me exactly what problem you face.

- Coordinate system. Is the model coodinate system related to survey coordinates? (EPSG codes for UTM-like or similar Transversal Mercator grids)

- OBJ axis orientation: Use obj_order=XYZ/XZY/... as needed

- model appears blocky and jitters. Must appear broken already in Meshlab. Coordinates are in full UTM or similar coordinates.  Solution: Find a way to make smaller coordinate values by subtracting full thousands of metres. Real-time graphics works best with single-precision floating point numbers with all limitations.

-...

Are there messages in the Logfile?

G.

[Antwane Lee]

Georg:

Thanks for the response.

I will work on it and see if I have any questions.

Thank you.

Antwane

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[Dave Pentecost]

Hi Georg - Thanks for the amazing work. I enjoyed meeting you in Vienna in fall 2023! I am finally tackling using Stellarium in Unity for an archaeoastronomy dome show about Palenque, and I ran across the Stellarium Unity bridge: https://github.com/Stellarium/stellarium-unity

As I start working with this, a couple of questions.

Is there a particular version of Unity that this works best with? I am guessing 2019.x based on the last updates of the repo.

Would there happen to be a preconfigured sample Unity project that's available? 

Thanks again! I will probably have some other questions about the set up. I'll let you know.

Dave

[Georg Zotti]

Hi!

Thanks for your interest. Unfortunately after developing this which was extended in the Garden of Instruments as proof of concept in 2018 (https://homepage.univie.ac.at/georg.zotti/InstrumentPark/index.html) there was no further interest from the world for me to get involved in any astro-related Unity project, and no interesting data (georeferenced building model assembly) that would not just fit inside Stellarium or require game-like interaction came upon me to motivate myself to play around or ever upgrade to any later version. Virtual archaeoastronomy works, looks great, is interesting and engaging, but doesn't currently pay the bills for me.

In the README I found myself having left a note on Unity versions 5.4 and 2017. These should work. For later versions, maybe recreate the prefab following the instructions and adapt where necessary. I have used the json kit elsewhere, this has seen significant updates, but fixes were straightforward. 

A group from Japan has taken up where I stopped, see https://arcastrovr.org/en/index.html  There is no live sky background, only skybox mode, but they even have a dome rendering mode.

 HTH, G.

[Dave Pentecost]

Thanks Georg. This is helpful. I have managed to update some older Unity packages that I needed (fisheye camera and splat loader) so I may get lucky. Yes, archaeoastronomy does not pay my bills either!

Dave

@dpentecost
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[Dave Pentecost]

Hi Georg - The ArcAstroVR project is fascinating. I think I could work with this even though I am primarily on Mac. At the very least I can use your skybox.ssc script to generate skyboxes for Unity, with my own terrain and Palenque site model.

I will play with that. I don't expect you to support any of that.

BUT I have a mystery using your skybox.ssc script. It generates 6 camera views, and I can make a skybox shader using those. But each view should be 60 degrees FOV and square, and they seem set for 90. See attached screenshot for the problem, and attached camera output from skybox.ssc. Each view has more than it needs horizontally, and there should be no overlap in a skybox. (top and bottom also seem to need rotating, but that can be dealt with)

Is there a setting in Stellarium that I am missing? a setting in Unity? a setting in the script that can be changed?

Thanks

Dave

@dpentecost
Cell 646 704 2021

[Dave Pentecost]

Whoops, sorry. Each view should be 90 degrees FOV, of course, 

@dpentecost
Cell 646 704 2021

[Georg Zotti]

Yes, 90 degrees. Then of course, 90°FOV means vertical FOV. The tiles should be squares, so just trim left and right if needed. (Or manually set screenshot size.)

[Dave Pentecost]

Thanks. I could do that if there's no other fix. A bit tedious if you are working with multiple alignments. (As thanks for your time, please accept the attached paper on observations at Palenque, written by my Chiapas friends.)

But it makes me wonder how it works in ArcAstroVR/Stellarium on Windows. If I find out I will let you know.

Dave

@dpentecost
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[Georg Zotti]

Not so tedious. You can either trim the texture by using my Unity loader script (I think it does make sure it will be square. Given that arcAstroVR uses my linking package I assume it kept this function.), or already configure a manual screenshot size which is square (this saves the additional trimming step). See Fig 4.7 in the User Guide.

Thanks for the paper, I hope you can soon replicate the light effects!

Georg

[Dave Pentecost]

Okay, after manual trimming, etc. here is a sample render from Unity. Proof of concept and all. Archaeolines test coming. 

https://drive.google.com/file/d/16NH9YL7o53tjhNNHte5n-KHodPfPj2W0/view?usp=share_link

This render does not have proper tilt for actual dome use, but I like the looks of the model. 

Here is one closer to the correct tilt for a tilted dome. 

https://drive.google.com/file/d/1g4VuU15zPIAfEExAG3MYawubkiz3RETq/view?usp=share_link

Full render is 4096X4096, 60 fps. 

Looking at the script - if we could change the *horizontal* FOV to 90 for the 6 views we'd really be cooking. 

Thanks for this great tool.

Dave

Cheers

Dave

@dpentecost
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[Georg Zotti]

Please follow my hints. Go into Stellarium's settings dialog and set screenshot size to 4096x4096 (or even 8192x8192 if your GPU does it), select image format, and you are set to square tiles. And then please don't switch off the atmosphere. Palenque is not on the Moon.

[Dave Pentecost]

Thanks for the "hint" - that fixes the square tile issue, but the top and bottom tiles are still rotated 90 degrees. That is easily fixed. 

Onward!

@dpentecost
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[Georg Zotti]

There's no standard for that I think. Or there are 4 or even 8 :-P... My Stellarium script works with my Unity skybox. YMMV.

G.

[Dave Pentecost]

Hi Georg - Having fun making skyboxes with archaeolines. Thanks again for your help. 

See this link to a one-minute video - a first flythrough of the Palenque model, ending with the alignment of the Temple of the Sun with the major lunar extent. It will happen this year on Nov. 8, at 7am.

https://drive.google.com/file/d/1oqY0SZaLrfI5tH7vZh5Zmtzh-KGpuxJm/view?usp=share_link

It is a dome formatted video, in low resolution, but I am able to render out 4096X4096 which will look great in the planetarium. Workflow for anyone else trying this: Stellarium -> skybox.ssc script -> Unity skybox -> fulldome camera (Github) -> Unity timeline -> Unity Recorder.

I am about to edit your archaeolines plug-in, to remove the labels. Please stop me! Actually, if you have a hint for how to do it (which lines, what changes) I would appreciate it. Otherwise I will follow Claude AI's advice. You can see in the video that making the skybox doubles up the labels on both sides of the lines. Gets messy.

I saw in some note that you say that Stellarium does not like zenith or nadir views. This could be why I need to rotate top and bottom views in the cubemap. Not a big deal.

Anyway, archaeolines and skybox.ssc are great tools for my purposes. I'll remind you that I am (stubbornly) on Mac so most of the arcAstroVR and Stellarium-to-Unity tools do not work for me. Oh, for a Syphon output from Stellarium!

Cheers

Dave

[Georg Zotti]

The skybox script calls a special mode which does create proper zenith/nadir views. Whatever script you then use in Unity to assemble the skybox expects top/bottom tiles in a different orientation than my own Unity skybox. That's all. 

Syphon... In 2015 someone on a Mac suggested we'd support Syphon.  Around 2016 I read about Spout, "like Syphon for Windows". Days later we provided Spout output.  Since then, no Mac user has provided the ~150 corresponding lines for Macs. Want some hero points?

[Dave Pentecost]

Thanks, but I'm no hero. I asked my coder friend (who created Syphon) to consider doing it a couple of times, then gave up. The stopgap I found was a free app called Syphoner, which allows you to choose any app or window as the Syphon server source. Stellarium pops up as a source. I send the equirectangular output of Stellarium (no labels on the Archaeolines!) to the skybox of Unity. It's a hack but it's working so far.

For any future heroes, here is the Syphon repo: https://github.com/syphon

Dave

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