quantized-mesh-tile-cs

A .NET Standard 2.0 library for encoding/decoding a terrain tile (quantized mesh format).

More info about the quantized mesh format: https://github.com/AnalyticalGraphicsInc/quantized-mesh

For more awesome quantized mesh implementations see https://github.com/bertt/awesome-quantized-mesh-tiles

Installation

PM> Install-Package quantized-mesh-tile

Usage: Decoding

const string terrainTileUrl = @"https://geodan.github.io/terrain/samples/heuvelrug/tiles/13/8432/6467.terrain";

var client = new HttpClient();
var stream = await client.GetStreamAsync(terrainTileUrl);
var terrainTile = TerrainTileParser.Parse(stream);
Console.WriteLine("Number of vertices: " + terrainTile.VertexData.vertexCount);
Console.ReadLine();

Usage: Encoding

Encode a list of WKT POLYGON Z triangles into a quantized-mesh tile byte stream. The tile coordinates (z, x, y) follow the TMS scheme and determine the geographic extent.

var triangles = new List<string>
{
    "POLYGON Z ((7.38 44.65 303, 7.38 45.0 320, 7.56 44.82 310, 7.38 44.65 303))",
    "POLYGON Z ((7.38 44.65 303, 7.73 44.65 350, 7.56 44.82 310, 7.38 44.65 303))"
};

byte[] bytes = TerrainTileEncoder.Encode(triangles, z: 9, x: 533, y: 383);
File.WriteAllBytes("output.terrain", bytes);

The encoder:

• Deduplicates vertices and quantizes coordinates to [0, 32767]
• Computes the tile header (ECEF center, bounding sphere, height range)
• Identifies edge vertices (west, south, east, north borders)
• Serializes all sections to the quantized-mesh binary format

Benchmark

|                    Method |     Mean |    Error |   StdDev |
|-------------------------- |---------:|---------:|---------:|
| ParseVectorTileFromStream | 46.74 us | 0.099 us | 0.087 us |

Sample: convert to GeoJSON

See samples/qm2geojson, sample code for converting a quantized mesh tile to GeoJSON.

Result: see https://github.com/bertt/quantized-mesh-tile-cs/blob/master/samples/qm2geojson/triangles.geojson

Sample visualization:

History

26-04-22: release version 0.5 with quantized-mesh tile encoding support

23-05-26: release version 0.4 to .NET 6

18-12-28: release version 0.3 with BinaryReader instead of FastBinaryReader

18-12-05: release version 0.2 with new .NET project file and conversion to WGS84 (method GetTriangles) removed.