Gaia Sky VR

Gaia Mission

• Gaia is ESA's cornerstone astrometry mission
  • Surveys the sky since late 2013 → largest star catalog to date


• Data products:
  • DR1: Data release 1 (Sep. 2016)
  • DR2: Data release 2 (Apr. 2018)
  • DR3: Data release 3 (Jun. 2022)

Gaia Sky

• 3D Universe software platform similar to Celestia or OpenSpace
• Multiplatform → Linux, Windows, macOS
• Open source and libre
• Focus on Gaia and its data
• Outreach material production

Gaia Sky Features

• 4 camera modes
• Seamless navigation
• 6D exploration → $x$ + $\mu$
• Full VR support
• Billion-stars catalogs → LOD
• Panorama, planetarium, orthosphere
• Stereoscopic mode (3D)
• Sparse virtual textures

• Elevation (w. tessellation)
• Eclipse representation
• Arbitrary datasets → VOTable, FITS, csv
• Filtering and color mapping
• SAMP integration
• Camera paths and keyframing
• Scripting API
• Many more...

Operation Modes

• Default, single-view mode
• Virtual Reality
• Panorama ($360^\circ$)
• Planetarium
• Orhtosphere
• Stereoscopic (3D)
• Multiple projectors with MPCDI

Gaia Sky VR

How did it come about?

• Feb. 2014 → Gaia Sky development starts
• May 2018 → first Gaia Sky VR in 2.0.0 using SteamVR OpenVR
• Sep. 2019 → VR merged into main app in 2.2.1
• July 2023 → migration to OpenXR in 3.5.0

Gaia Sky is first and foremost a desktop application

Gaia Sky VR

• VR mode using the OpenXR API directly
• Full feature set of base desktop app
• Minimalist approach:
  • As similar as possible to base Gaia Sky
  • Free navigation using VR controllers
  • Point&shoot for object selection
  • In-scene control panel

Panorama Mode

• Render 6 scenes with $fov=90^\circ$
  • +X, -X, +Y, -Y, +Z, -Z
• Use those to create a cubemap
• Project to screen:
  • Equirectangular (spherical)
  • Cylindrical
  • Hammer

Planetarium Mode

• Single projector setup
  • Uses cubemap from panorama mode
  • Azimuthal projection (Domemaster)
  • Configurable FOV → Can be greater than $180^\circ$
• Multi-projector setup
  • MPCDI (Multiple Projection Common Data Interchange)
  • Defines warp, frustum, etc. for each projector

Orthosphere Mode

• Also use cubemap
• Render two halves of sphere w. Azimuthal
• Blend them together
• Wrap scene around in sphere

Stereoscopic Mode

• 7 profiles:
  • 3DTV horizontal
  • 3DTV vertical
  • Anaglyph red/cyan and red/blue
  • Cross-eye, parallel view
  • VR simulation

Dataset Manager

Gaia Sky features a built-in Dataset manager

• Connects to our data repository
• Used to download, update and enable/disable datasets

Dataset Types

• Stars → positions + other star attributes
• Variable stars → same as stars + light curves
• Particles → positions only
• Other catalogs → clusters, nebuale, iso-surfaces, etc.
• Custom objects → models, billboards, ray-marched, etc.
• SVTs → Sparse Vritual Textures

Star Datasets

$\alpha$, $\delta$, $\varpi$, $\mu_{\alpha}$, $\mu_{\delta}$, $\rho$, magnitudes, colors, names, constellations, etc.

• Regular datasets → thousands to a few million objects
• LOD (level-of-detail) → billions of objects

Regular Star Datasets

• Gaia-based:
  • DR3 tiny → 2.5M stars, 1%/0.01% bright/faint pllx. rel. err.
  • DR3 weeny → 1.9M stars, 0.8%/0.01% bright/faint pllx. rel. err.
  • DR3 variables → 186K Cepheid and RR Lyrae
  • eDR3 white dwarfs → 359K WDs
  • eDR3 GCNS → 300K stars within 100 pc
• Other sources:
  • Hipparcos (new reduction) → 120K stars
  • CNS5 → 5931 nearby stars, eDR3 + Hipparcos
  • SAMP, VOTable, CSV, etc. → Load your own datasets

LOD Datasets

LOD Datasets (DR3)

Table: DR3 Gaia Sky datasets (compressed sizes)

Systems

• Star systems based on Gaia DR3
• Gaia BH2, GI876, HD114762, HD40503, J0805+4812, etc.

Galaxies

• NEARGALCAT → 875 close-by galaxies
• SDSS → high-redshift galaxies and objects
  • DR12 → 327K
  • DR14 → 3M
  • DR17 → 2.8M
  • DR18 → 3.6M

Star Clusters

MWSC (~3K), OCDR2 (~2K), Hunt-Reffert (~7K)

Asteroids

From orbital elements → 150K DR3 asteroids

Maps

Iso-density surfaces for hot stars, HII regions, dust clouds

Maps

Inner view of dust (black), hot-stars (blue) and HII (red)

Sparse Virtual Textures (SVT)

• Earth
  • Surface (NASA VE) → 128K
  • Topography (USGS) → 128K
  • Clouds (Van Vliet) → 32K
• Moon
  • Surface (Van Vliet) → 64K
  • Topography (LRO WAC DTM) → 8K
• Mars
  • Surface (Van Vliet) → 64K
  • Topography (MOLA/USGS) → 64K

System Overview

• User interface
• Event manager
• Object model
• Rendering system
• Scripting engine

Language Breakdown

As of November 2023

--------------------------------------------------------------------------------------
Language                      files          blank           comment              code
--------------------------------------------------------------------------------------
Java                           1174          27765             40274            172917
GLSL                            150           2546              2175             10026
Properties                       18           1130              8537              8618
JSON                             11              6                 0              7124
XML                               4              2                 4              6277
Python                           87           1744              1037              4779
Markdown                         12            765                 0              3065
YAML                              4             46               744               640
Gradle                            3            113                76               621
Bourne Again Shell                9            102               137               286
Bourne Shell                      6             45               134               171
HTML                              2              7                 0                91
--------------------------------------------------------------------------------------
SUM:                           1493          34350             53164            217137
--------------------------------------------------------------------------------------
            

Making Videos

Tools to produce videos with Gaia Sky

• Record/playback camera paths
  • Define paths visually with keyframes
• Still frame output mode → +ffmpeg
• Arbitrary resolution export
• Combine with scripting

Scripting

• Python API → via Py4j
• Run code snippets after every frame
• Manipulate camera
• Control GUI
• Add, remove, modify objects
• Control time
• Much more: scripting docs

Dataset Filtering and Color Mapping

• Multiple arbitrary filters on dataset attributes
• Color map any attribute

SAMP Integration

• Gaia Sky is a SAMP client
• Send datasets from Topcat, Aladin, etc.
• Tables mapped to 3D cart. or sph. coords + mags + colors
• Selection works both ways

Metadata Format

• Open format based on JSON
• Simple and easy syntax
• Well-documented
• Define objects and their attributes
• Define and load datasets/catalogs

Interested in Gaia Sky?

Home Page

zah.uni-heidelberg.de/gaia/outreach/gaiasky

Documentation

gaia.ari.uni-heidelberg.de/gaiasky/docs

Source Repository

codeberg.org/gaiasky/gaiasky

Thank You