Tangram NG

Fork of Tangram ES for Ascend Maps

Cross-platform C++ library for rendering 2D and 3D maps, supporting vector (GeoJSON, TopoJSON, Mapbox Vector Tiles) and raster (PNG, JPEG, TIFF, and LERC) data.

Map style is defined by YAML scene files - see Tangram ES documentation at https://tangrams.readthedocs.io

Diff to upstream: compare/076b273..HEAD

Major changes include:

• 3D terrain support (incl. label occlusion, sky, etc.)
• eliminating duplicate tile loads (when a source is used multiple times)
• tile level-of-detail based on screen area (in pixels**2)
• try proxy tile if tile loading fails (for better offline support)
• TIFF and LERC raster support
• GLES 3 support
• support for native scene style functions (performance improvement over JS)
• support for MBTiles as cache for online source, incl. last access tracking and max-age
• optional fallback marker shown when a marker is hidden by collision
• support for zoom_offset < 0 (for better satellite imagery resolution when pixel scale > 1)
• contour line label support
• support JS function for generating tile URL (per tile)
• $latitude, $longitude in scene style for location dependent styling adjustments
• support SVG images embedded in scene style (with external SVG renderer, e.g., nanosvg)
• support for fixed boolean values in filters to allow use of scene globals
• canceling all URL requests when destroying Scene
• misc optimizations based on profiling
• support plain makefile build
• fix some proxy tile issues (e.g. cycles)
• fix some issues when very large number of labels present
• fix some crashes related to async Scene destruction

Dependency changes:

• make glm and stb submodules
• absorb tangrams/* submodules
• replace SQLiteCpp with simple single header (200LOC) sqlite C++ wrapper
• replace old yaml-cpp with custom yaml/json library (to fix crashes)

Demo

Ascend Maps uses a cross-plaform GUI framework (ugui) instead of native GUI. For examples of how to integrate tangram-ng with more conventional native apps, see the demos in the platforms folder (note that the platform-specific documentation has not been updated yet). The scene file osm-bright.yaml was converted from Mapbox style JSON using mb2mz.js.

To build the demos (requires cmake):

• Linux: make linux to create build/Release/tangram
• Android: cd platforms/android && ./gradlew installRelease (update ndkVersion in tangram/build.gradle as needed)
• iOS, macOS, Windows: demos not yet updated from tangram-es versions, please open a github issue if needed

More

Contains a couple potentially useful libraries:

• gaml - simple (~1000 LOC, 2 files) YAML parser and writer, supporting both block and flow style. Can preserve comments and order of map keys
• sqlitepp - single header (~200 LOC) wrapper for sqlite supporting expressions like db.stmt("select a,b,c from some_table where d = ? and e = ?;").bind(5, "foo").exec([&](int a, float b, std::string c) { /* called for each result row */ });

Contributing

Contributions are welcome, but please open an issue or discussion before starting on major changes.