# 首页素材来源与授权 / Homepage image sources

Every image on the homepage (`/index.html`) is a real simulation output, a render of
experimental structure data, a software screenshot, or an on-site photograph. None are
AI-generated, and none have been repainted or given invented data overlays. The only
edits are resizing, cropping (hero only), re-encoding to WebP/JPEG, and flattening PNG
transparency onto black. All files can be regenerated from the originals with
`python3 scripts/fetch-assets.py`.

NVIDIA and Ansys appear on the page **only as text links** to their public product or
documentation pages. Their newsroom and website images were not used:
NVIDIA's website terms (<https://www.nvidia.com/en-us/about-nvidia/terms-of-service/>,
§3.1–3.2) limit downloaded materials to "personal, non-commercial internal use" and
prohibit "public display". The community is not affiliated with NVIDIA, Ansys/Synopsys,
NASA, Tesla, Wikimedia, or any other organisation named here.

| # | Homepage slot | Files in `/assets/img/` | What it shows | Owner / author | Licence | Source page | On-page credit |
|---|---|---|---|---|---|---|---|
| 1 | Hero (aero CFD) | `hero-f16-openfoam-{1600,2400}`, `hero-f16-openfoam-m-{800,1200}` (`.webp`/`.jpg`) | ParaView visualisation of an OpenFOAM simulation of an F-16: surface pressure distribution and streamlines. Desktop crop: x 960–3840; mobile crop: x 1900–3700, y 80–1080 of the 3840×1080 original. | Marek Cel (Wikimedia Commons user Cel 84), own work, 2020-09-24 | **CC0 1.0** public-domain dedication | <https://commons.wikimedia.org/wiki/File:3840x1080_F16_OpenFOAM.jpg> | "图：Marek Cel · CC0 · Wikimedia Commons" |
| 2 | 制药 · Drug discovery | `drug-7si9-mpro-{720,1280}` | Electrostatic surface of the SARS-CoV-2 main protease (Mpro/3CLpro) crystal structure PDB 7SI9, with inhibitor PF-07321332 (nirmatrelvir) as grey sticks. | Vcpmartin (Wikimedia Commons), own work, 2021-11-05. Underlying coordinates: PDB 7SI9 (wwPDB data, CC0). | **CC BY-SA 4.0**. Our resized derivative is shared under the same licence. | <https://commons.wikimedia.org/wiki/File:7si9_surface.png> · structure: <https://www.rcsb.org/structure/7SI9> | "图：Vcpmartin，基于 PDB 7SI9 晶体结构渲染 · CC BY-SA 4.0" |
| 3 | 气象 · Climate | `climate-nargis-nasa-{720,1200}` | Snapshot of a NASA simulation of Cyclone Nargis (April 2008), run on the Pleiades supercomputer. Wind altitude by colour (blue low, pink high), wind speed by colour density. Timestamp and colour bar are part of the original image. NASA ID `ARC-2012-ACD12-0020-002`. | NASA Ames Research Center. Credit: Bryan Green (NASA Ames), Bo-wen Shen (NASA Goddard). | **Public domain** (US government work). NASA media guidelines: <https://www.nasa.gov/nasa-brand-center/images-and-media/>. No NASA endorsement implied. | <https://images.nasa.gov/details/ARC-2012-ACD12-0020-002> | "图：Bryan Green（NASA Ames）、Bo-wen Shen（NASA Goddard）· 公有领域" |
| 4 | 机械 · 电气 · Robots / digital twin | `robot-tesla-fremont-{800,1600}` | Tesla Fremont factory, 2011-10-05: an industrial robot installs the laminated glass roof on a Model S body (from the photographer's caption). | Steve Jurvetson (Flickr) | **CC BY 2.0** (verified by the Wikimedia Flickr review bot on 2013-02-23) | Flickr: <https://www.flickr.com/photos/44124348109@N01/6219463656> · Commons mirror: <https://commons.wikimedia.org/wiki/File:Tesla_auto_bots.jpg> | "图：Steve Jurvetson · CC BY 2.0" |
| 5 | 化工 · Process | `chem-dwsim-gibbs-{720,1280}` | Screenshot of the open-source process simulator DWSIM 5.0 on macOS: "Gibbs and Equilibrium Reactors" sample (equilibrium composition of CH₄/H₂O/CO/CO₂/H₂ at 1000 K, 1 bar) with the equilibrium-reaction editor open. | DanWBR (Daniel Medeiros, DWSIM author), own work, 2017-09-01 | **CC BY-SA 4.0** (dual-licensed with GFDL; we use CC BY-SA 4.0). Our resized derivative is shared under the same licence. | <https://commons.wikimedia.org/wiki/File:DWSIM_v5_running_on_macOS.png> | "图：DanWBR（DWSIM 作者）· CC BY-SA 4.0" |

## Hero video (loops over the static hero image)

| Slot | Files in `/assets/video/` | What it shows | Owner / author | Licence | Source page | On-page credit |
|---|---|---|---|---|---|---|
| Hero (motion) | `hero-rotor-nasa-1280.webm` (1.8 MB, VP9), `hero-rotor-nasa-1280.mp4` (2.1 MB, H.264), `hero-rotor-nasa-854.mp4` (1.0 MB, H.264, mobile), `hero-rotor-nasa-poster.jpg` | About 9.4 s, silent, from NASA's SC20 aeronautics CFD reel "Our Aeronautics Research is a Thing of Beauty" (NASA ID `NHQ20201221ARMD`). Two consecutive supercomputer CFD shots of rotor wakes on a test stand (source timecodes 31.75–37.25 s and 37.42–42.50 s), joined with a 0.6 s dissolve; the end dissolves back into the start for a seamless loop. Audio removed; scaled to 1280/854 px. Not cropped or recoloured, and the burned-in "Credit: Jasim Ahmad" is left in the file. | NASA Advanced Supercomputing Division, NASA Ames Research Center. Visualization credit (burned in): Jasim Ahmad. | **Public domain** (US government work). NASA media guidelines: <https://www.nasa.gov/nasa-brand-center/images-and-media/>. No NASA endorsement implied. | <https://images.nasa.gov/details/NHQ20201221ARMD> · original: <https://images-assets.nasa.gov/video/NHQ20201221ARMD/NHQ20201221ARMD~orig.mp4> | "视频：NASA Ames / Jasim Ahmad · 公有领域 · NASA Image Library" (shown in the hero caption while the video is playing) |

How the hero behaves: the static F-16 image (row 1) is always rendered first and is the LCP element. After `load`, a script creates a muted, looping, `playsinline` `<video>`, and fades it in only once it fires `playing`. It is skipped entirely when `prefers-reduced-motion: reduce` is set, on Save-Data, or on 2G connections. It is abandoned (image stays) if playback is blocked, errors, or hasn't started within 10 s. The caption switches to the video credit only while the video is visible. Rebuild with `scripts/build-hero-video.sh`.

Video candidates considered and rejected: the Commons von Kármán street, Kolmogorov scalar-transport and gravity-current clips (CC BY-SA; white matplotlib backgrounds, or under 2 fps); NASA Orion launch-abort CFD (public domain, but a pale cyan/blue background); NASA GEOS-5 2017 aerosol simulation (public domain and dark, but a climate scene with burned-in map legends that compete with the hero text).

## Original-file URLs used by `scripts/fetch-assets.py`

1. <https://upload.wikimedia.org/wikipedia/commons/b/bd/3840x1080_F16_OpenFOAM.jpg>
2. <https://upload.wikimedia.org/wikipedia/commons/f/fa/7si9_surface.png>
3. <https://images-assets.nasa.gov/image/ARC-2012-ACD12-0020-002/ARC-2012-ACD12-0020-002~orig.jpg>
4. <https://upload.wikimedia.org/wikipedia/commons/5/57/Tesla_auto_bots.jpg>
5. <https://upload.wikimedia.org/wikipedia/commons/9/95/DWSIM_v5_running_on_macOS.png>

## Text-only "延伸" links (no images taken from these pages)

- NVIDIA BioNeMo Framework docs: <https://docs.nvidia.com/bionemo-framework/latest/>
- NVIDIA Earth-2: <https://www.nvidia.com/en-us/high-performance-computing/earth-2/>
- NVIDIA Isaac Sim: <https://developer.nvidia.com/isaac/sim>
- NVIDIA Omniverse: <https://www.nvidia.com/en-us/omniverse/>
- Ansys Fluent: <https://www.ansys.com/products/fluids/ansys-fluent>
- Ansys Chemkin: <https://www.ansys.com/products/fluids/ansys-chemkin-pro>
- RCSB PDB 7SI9: <https://www.rcsb.org/structure/7SI9>
- NASA Advanced Supercomputing: <https://www.nas.nasa.gov/>
- DWSIM: <https://dwsim.org/>

## Considered and rejected

- **NVIDIA newsroom / blog / Earth-2 / Isaac / BioNeMo imagery**: the site terms allow only personal, non-commercial internal use and prohibit public display. These are linked, not rehosted.
- **Ansys (now Synopsys) product imagery**: no public reuse licence was found, so it is linked only.
- **YouTube embeds of official NVIDIA/Ansys videos**: allowed by YouTube's terms, but YouTube is unreachable for most visitors in mainland China, which would leave blank cards. Not used.
- **NETL MFiX gallery (multiphase reactor CFD)**: the Flickr originals are marked "All rights reserved". Not used.
- **"CFD visualisation of leading-edge vortex breakdown over a 65° delta wing" (Commons, CC0)**: uploaded October 2026 by an unverified account, so its provenance was too new to vouch for. Not used.
- **NASA X-43A Mach 7 CFD and nose-landing-gear CFD** (public domain): authentic, but the white backgrounds clash with the dark hero. Kept as fallbacks.