BlueMarble

Live NASA Blue Marble wallpaper for Windows — your desktop always shows Earth as it looks right now, with the real-time day/night terminator, city lights on the dark side, and ocean glint on the sunlit side.

What it does

• Downloads daytime (Blue Marble Next Generation) and nighttime (Black Marble / VIIRS city lights) imagery from NASA GIBS.
• Computes the subsolar point from the current UTC time and blends day & night through a soft terminator.
• Re-renders and applies the wallpaper every 5 minutes (configurable), so the terminator tracks real solar position.
• On multi-monitor setups, generates a separate image per display at its native pixel resolution and applies it via IDesktopWallpaper — no upscaling blur, no distortion, no matter how different the resolutions or DPI scales are.
• Lives in the system tray (no taskbar window). Right-click for pause / force refresh / exit.

Requirements

• Windows 10 1809 (build 17763) or newer, x64 or ARM64.
• Internet access on first launch (and after each midnight UTC) to fetch fresh imagery from NASA GIBS. Imagery is cached locally under %LOCALAPPDATA%\BlueMarble\cache.

The published binary is self-contained: no .NET runtime install needed.

Installation

Option A — Pre-built binary

1. Download BlueMarble-v1.0.0-win-x64.zip from the latest release.
2. Extract the whole folder anywhere you like, e.g. %LOCALAPPDATA%\Programs\BlueMarble\. Keep BlueMarble.exe together with its sibling DLLs and Assets folder — the build is self-contained but not a single file, so the .exe won't run on its own.
3. Double-click BlueMarble.exe to run. A globe icon appears in the system tray.
4. (Optional) To auto-start at login, add the path to HKCU\Software\Microsoft\Windows\CurrentVersion\Run:

   New-ItemProperty -Path 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Run' `
     -Name BlueMarble `
     -Value "$env:LOCALAPPDATA\Programs\BlueMarble\BlueMarble.exe" `
     -PropertyType String -Force

Option B — Build from source

Prerequisites:

• Visual Studio Build Tools 2022 (the standalone .NET SDK is not enough — see the note below).
• The Windows App SDK workload is pulled in automatically via NuGet.

git clone https://github.com/EmereArco/BlueMarble.git
cd BlueMarble

# Run tests (pure .NET, dotnet CLI works fine for these)
dotnet test BlueMarble.Tests/BlueMarble.Tests.csproj -c Debug

# Publish a self-contained release (x64) — produces a folder, not a single file
& "C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\MSBuild\Current\Bin\MSBuild.exe" `
  BlueMarble\BlueMarble.csproj `
  -t:Publish `
  -p:Configuration=Release `
  -p:Platform=x64 `
  -p:RuntimeIdentifier=win-x64

Output folder: BlueMarble\bin\x64\Release\net8.0-windows10.0.19041.0\win-x64\publish\ — run BlueMarble.exe from there (it needs the surrounding DLLs).

For ARM64, replace x64 / win-x64 with ARM64 / win-arm64.

Why MSBuild and not dotnet build? WindowsAppSDK 1.6's MrtCore.PriGen.targets resolves Microsoft.Build.Packaging.Pri.Tasks.dll relative to the running MSBuild root. VS Build Tools' MSBuild finds it under …\BuildTools\MSBuild\…\AppxPackage\; the standalone .NET SDK doesn't ship an equivalent. This is an environment constraint, not a project bug.

Configuration

Settings live in %LOCALAPPDATA%\BlueMarble\settings.json (created on first run with defaults). Edit and restart the app to apply.

Key	Default	Meaning
refreshInterval	00:05:00	How often the wallpaper is re-composed (min 1 minute).
outputWidth / outputHeight	3840 / 2160	Fallback master frame size when no monitor is enumerated; on multi-monitor setups the size is derived from the largest display (capped at 8192 px).
terminatorSoftnessDegrees	22.0	Half-width of the dawn/dusk blend band.
oceanGlintStrength	0.6	Intensity of the subsolar specular highlight (0 to disable).
oceanGlintRadiusDegrees	35.0	Angular spread of the glint.
wallpaperPosition	Fit (3)	Used only on the single-image fallback path; per-monitor frames are always sized exactly to their display.
launchAtLogin, pauseOnBattery, pauseOnFullscreenApp	reserved	Wired into settings, UI in progress.

The tray menu provides Pause, Refresh now, and Exit.

How it works

NASA GIBS WMS                       Tile cache                Composer                   Per-monitor framer
(blue-marble-ng,                    (%LOCALAPPDATA%           (Skia, soft                (letterbox to each
 black-marble VIIRS)  ──fetch──▶    \BlueMarble\cache)  ──▶   terminator + glint)  ──▶   monitor's native size)
                                                                                                  │
                                                                                                  ▼
                                                                                       IDesktopWallpaper::SetWallpaper
                                                                                       (one image per monitor ID)

The solar geometry uses the standard equation of time + declination approximations for the subsolar point; the terminator is the locus where cos(solar zenith angle) crosses zero, soft-stepped across terminatorSoftnessDegrees. See BlueMarble/Composition/SolarGeometry.cs and FrameComposer.cs.

Project layout

BlueMarble/
├── Imagery/        GIBS WMS client, tile cache, day/night providers
├── Composition/    SolarGeometry, FrameComposer, MonitorFrame   (pure — tested)
├── Wallpaper/      WallpaperApplier, MonitorEnumerator          (Position pure)
├── UI/             TrayIconHost, PrefetchRefreshController, RefreshScheduler
├── Native/         P/Invoke, IDesktopWallpaper COM interop
└── Settings/       AppSettings + JSON store
BlueMarble.Tests/   xUnit, links pure files from the main project

Credits

• Imagery: NASA Earth Observatory Blue Marble Next Generation (2004) and VIIRS Black Marble (2016), served via NASA GIBS.
• Composition is done with SkiaSharp; the tray icon uses H.NotifyIcon.WinUI.

License

To be decided. Until a license file is added, all rights reserved.