# Io scene B ("Tarawera fissure" → `io.tvashtar`): credits and data provenance

Helios is non-commercial. Every source below is used under its stated licence. **Real data** means measured elevation or scanned geometry/texture. **Procedural** means generated by our scripts. The map is a real Earth landscape (Mt Tarawera, Aotearoa New Zealand) re-dressed as Io. None of it is Io topography.

## Elevation (real data)
| What | Source and citation | Licence | How we changed it |
| --- | --- | --- | --- |
| Base terrain, whole 7.168 km map (EPSG:2193 E 1902200–1909368, N 5758732–5765900) | *Bay of Plenty LiDAR 1m DEM (2019–2022)*, BOPLASS / Toitū Te Whenua Land Information New Zealand, `[path removed]` tiles BF38_10000_0101, _0102, _0201, _0202 (LERC COGs, read with rasterio) | CC BY 4.0 | Used at its native 1 m. One isolated spike removed. OSM tracks inpainted (see below). Lakes Rotomahana and Tarawera (hydro-flattened in the DEM) raised by 5 m and flooded as lava plains, with a procedural 2.5 m marginal rim, a 2 m central sag and Big Obsidian pressure-ridge relief. Kit-bash additions are listed below. Heights shifted by −600 m for the world frame. |
| Context apron outside the map (24 km) | Same LINZ dataset, 30 tiles (BE37/BE38/BF37/BF38) read at 16 m and resampled to 32 m | CC BY 4.0 | Not modified apart from resampling; the lakes stay flat. |
| Fissure-B spatter-cone row | U.S. Geological Survey 3DEP 1 m DEM (Great Rift, Big Craters and Spatter Cones, Craters of the Moon, Idaho) | Public domain | A 1.1 km strip along the cone chain, detrended (σ 90 m), rotated and scaled (×0.9 horizontally) onto the 1 km fissure-B line, relief ×1.3, with side and end feathers of 70 m and 140 m. |
| Collapse pit beside the hub | Polar Geospatial Center, *ArcticDEM mosaic v4.1, 2 m* (tiles 75_24_2_2 and 75_24_1_2), Plosky Tolbachik summit pit, Kamchatka | CC BY 4.0 (PGC; credit "DEM(s) provided by the Polar Geospatial Center under NSF-OPP awards 1043681, 1559691, 1542736, 1810976 and 2129685") | The pit was cut out against an inpainted surround (900 m radius, 160 m feather) and scaled by 0.28 both horizontally and vertically, so its wall angles stay real. The donor's positive relief outside the pit (summit ridges) is capped at 5 m and smoothed. It is about 500 m across and 139 m deep, and is added to the base at world (−2050, −520). |
| Flow-field surface texture (relief only) | INGV Pisa, *2004–05 Mt. Etna compound lava flow field: orthophotos and topography*, lidar of 29 Sep 2005 at 1 m, https://www.pi.ingv.it/banche-dati/2005-04-etna-lava-flow-data/ ; Favalli, Fornaciai & Pareschi (2009), Geomorphology 111, 123–135 | CC BY 4.0 | Cropped, detrended (σ 35 m), rotated to the flow direction, mirror-tiled, scaled ×0.35 and added inside the simulated flow outline with a 14 m feather. |
| Pressure ridges (relief only) | U.S. Geological Survey 3DEP, OPR 1 m DEM, Big Obsidian Flow (Newberry Volcano) | Public domain | Detrended (σ 25 m) and scaled ×0.12. Used on the distal flow lobes (more than 600 m from the vents) and, mirror-tiled, on the patera floors. |

## Human-artifact removal
OpenStreetMap contributors, Overpass API extract (maps.mail.ru mirror) of tracks, buildings and parking areas (© OpenStreetMap contributors, ODbL 1.0). It was used only to build the mask of what to inpaint (22 tracks, 1 road, 5 buildings; 0.32 km²); no OSM geometry ships with the scene. Footpaths into the chasm were deliberately left alone, so the crater walls are never inpainted.

## Textures (real scans and CC0 photo-textures)
| Layer | Source | Licence |
| --- | --- | --- |
| Sulfur yellow, iron red, salt white, mixed ochre, green crust and terrace pools (deposit and fumarole crusts) | Io asset kit `dallol-*` texture sets, cut from Grunwald, O.; Delage, E.; van Wyk de Vries, B., *Topographic 3D model: Dallol domes – Dataset*, OPGC / LMV, Université Clermont Auvergne, https://doi.org/10.25519/TXZC-1724 | CC BY-NC 4.0 |
| Fresh pahoehoe and patera crust | Io kit `basalt-pahoehoe-fresh`: "Lava field from Mauna Ulu – Kilauea, Hawaii" by Tom (trbaker), Sketchfab | CC BY 4.0 |
| 'a'a clinker | Io kit `basalt-aa-clinker` (ambientCG Rock031) | CC0 |
| Hot crust and crack pattern | Io kit `lava-crust-hot` (ambientCG Lava001) | CC0 |
| Cliff basalt (detail under the procedural bed colours) | Io kit `basalt-cliff` (Poly Haven Dark Rock 02, Amal Kumar) | CC0 |
| Scoria ground | Io kit `basalt-cinder-ground` (Poly Haven Terrain Red 01, Rob Tuytel) | CC0 |
| Weathered basalt | Io kit `basalt-old-weathered` (Poly Haven Dark Rock, Amal Kumar); Poly Haven `dark_rock` | CC0 |

## Scatter meshes (real scans)
These come from the Io asset kit (`[path removed]`). Our LOD1 and LOD2 are further quadric decimations. Exact credit lines per item are in `[path removed]`, copied from the kit manifest.
- `rock-aa-clinker-daal`, `rock-scoria-bomb-daal`: Digital Atlas of Ancient Life (Emily Hauf), Sketchfab, CC0.
- `rock-pahoehoe-block-kantanat` (kantanat), `rock-scoria-boulder` (fevenkitsune), `rock-sulfur-cianciana`, `rock-pahoehoe-slab-maunaulu` (trbaker), `rock-ropy-lobe-mangere`: Sketchfab, CC BY 4.0.
- `rock-vesicular-block-bustos` (Elan Bustos): CC BY 4.0 geometry, CC0 texture.
- `rock-basalt-block-ph07`, `rock-basalt-slab-ph09`: Poly Haven Rock 07 and Rock 09, CC0.
- `dallol-crust-mound`, `dallol-twin-mounds`, `dallol-salt-pillars`, `dallol-dark-mound-piece`: pieces of the OPGC Dallol domes model (doi:10.25519/TXZC-1724), CC BY-NC 4.0.

## Sky
Jupiter: NASA/ESA/A. Simon (GSFC), OPAL 2015 map (NASA SVS *Hubble Maps Jupiter in 4k Ultra HD*, https://svs.gsfc.nasa.gov/12021), public domain.

## Procedural (not data)
- **Fissure B and its position.** Fissure B is a design choice: an en-echelon segment that continues the real 1886 rift trend south-west toward Rotomahana. Only its cone relief is real (Great Rift).
- **Lava flows.** Flow outlines and thickness come from a cellular-automaton spread (residual-thickness model) of 16 overlapping units over the real topography.
- **Fissure features.** The spatter ramparts (2–4 m ridges), the jagged incandescent slot pieces and their crust bridges, the slot cuts (2–3 m), and the hot-channel levees and floor are all procedural.
- **Patera floors.** The raised marginal rim and central sag are procedural; the ridge relief is real data (Big Obsidian).
- **Sulfur deposits.** These come from an offline Io-ballistic particle simulation (g = 1.796 m/s², no atmosphere) of one chasm plume, fumarole bands derived from the real terrain (chasm rim lips, ledges and floor lows; the pit-rim lip) plus a hand-placed fissure-B polyline, and SO₂ frost from horizon-shadowed insolation and topographic lows. The parameters are in `[path removed]`.
- **Rendering effects.** These are all procedural: lava emission (crack networks, slots, channel, breakouts, cone throats), lava irradiance, the curtain-of-fire fountain particles, the plume volume and particles, fumarole steam, heat shimmer, the wall bed colours and the stars.
- **Placement.** Scatter placement and the vent, fumarole and hub positions are design choices.