vgl 1.0.0

The first release. vgl is a lightweight library for rendering a virtual globe inside an
existing application, behind a C API with a header-only C++ wrapper. The development history
before it is in the repository's commits.

Runtime

• Context (vgl/context.h): packs of elevation, imagery and the geoid, loaded through the
  host's I/O interface and layered by priority; imagery layers whose opacity and priority the
  host changes at run time; tile selection by screen-space error with frustum and horizon
  culling; tile meshes with skirts, built on the host's task interface; CPU, GPU and upload
  budgets; height queries above the ellipsoid or mean sea level; picking
  (vgl_context_ray_query); screen projection (vgl_view_project); statistics; and the
  attribution of the data in view.
• Render interface (vgl/render.h, docs/render-interface.md): frames of resources and
  draw lists with double-precision, camera-relative transforms, for the built-in backends and
  for hosts with their own renderer. Logarithmic, reversed-Z and conventional depth.
• Foundation and geodesy (vgl/foundation.h, vgl/geodesy.h): host allocators, logging,
  I/O and tasks; WGS84 and other ellipsoids, geodetic and ECEF conversions, local ENU frames and
  the Earth rotation angle, tested against GeographicLib.
• Defaults module (vgl/defaults.h, vgl::defaults): a thread pool, a file reader, an
  optional HTTP reader on libcurl (VGL_DEFAULTS_HTTP, the browser's fetch on WebAssembly), and
  a disk cache that keeps packs seen once available offline.
• Library rules: no exceptions across the API, buildable without exceptions and RTTI, no
  global state, no threads or connections created by the core, and every allocation through
  the host's allocator.

Backends

• OpenGL / OpenGL ES (vgl/gl.h, vgl::gl): OpenGL 3.3, OpenGL ES 3.0 and WebGL 2.
• Direct3D 11 (vgl/d3d11.h, vgl::d3d11): feature level 11_0, with shaders compiled at
  build time.
• Ogre (vgl/ogre.hpp, vgl::ogre): classic Ogre 14 on its OpenGL 3+ and Direct3D 11
  render systems, on Windows and Linux.
• Every backend draws up to four imagery layers per tile, an optional sea surface at the
  geoid, an atmosphere (sky, limb glow and haze), the host's stars and a cloud shell, with
  debug views (wireframe, level colours, imagery source, height colours) and contour lines.

Data and tools

• Pack format 1.0 (docs/pack-format.md): sharded, range-readable tile packs for
  elevation, imagery and the geoid, readable from local disk or any web server with HTTP range
  requests.
• Baker (vgl-bake, Windows and Linux, on GDAL 3.7 or later): deterministic, parallel and
  resumable bakes of elevation (with datum conversion and sea blending) and imagery, plus
  inspect, validate, query and check, which checks a hosted pack as vgl and browsers
  read it.
• Reference server (tools/server): a Caddy configuration for serving packs, with the
  hosting guide (docs/hosting.md). The project hosts no data: consumers bake and host their
  own packs.

Platforms, samples and packaging

• Windows 10, Linux, macOS 11 (universal), Android 7.0 (API 24, arm64), iOS 15 and WebAssembly
  with threads (Emscripten).
• Samples: OpenGL (also as a web page), Direct3D 11, Ogre, pure C and headless, with
  Google Earth style navigation, on small sample packs of Blue Marble, Sentinel-2 cloudless
  2016, Copernicus GLO-30, GEBCO and EGM2008 (samples/data).
• Release archives for Windows, Linux and macOS, shared and static; a vcpkg port and a Conan
  recipe (packaging); a CMake package (find_package(vgl)) and pkg-config files.
• Documentation: the design document and specifications in docs, and an integrator's guide
  in the wiki.

Known limitations

• The Ogre backend's Vulkan render system, macOS and the mobile platforms come after version 1
  (design document, milestone M3b).
• Imagery is stored as JPEG or PNG; WebP and compressed GPU textures (BC1, BC7) are reserved in
  the pack format but not supported yet.
• The Android and iOS builds are built in CI, but not yet run on a device, emulator or
  simulator.
• The release archives leave out the HTTP reader, which needs libcurl: use vcpkg, Conan or a
  source build for it. The static Windows archive links only into Release builds.