[core] Streaming TileCover for polygonal regions (#11267)

A per-tile streaming algorithm for tile cover on points, lines, and polygons. Works for individual zoom levels, and not zoom ranges.

1 files changed, 96 insertions, 0 deletions

diff --git a/benchmark/util/tilecover.benchmark.cpp b/benchmark/util/tilecover.benchmark.cpp
new file mode 100644
index 0000000000..186de6f216
--- /dev/null
+++ b/benchmark/util/tilecover.benchmark.cpp
@@ -0,0 +1,96 @@
+#include <benchmark/benchmark.h>
+#include <mbgl/util/geo.hpp>
+#include <mbgl/util/geometry.hpp>
+#include <mbgl/util/tile_coordinate.hpp>
+#include <mbgl/util/tile_cover.hpp>
+#include <mbgl/map/transform.hpp>
+
+using namespace mbgl;
+
+static const LatLngBounds sanFrancisco =
+    LatLngBounds::hull({ 37.6609, -122.5744 }, { 37.8271, -122.3204 });
+
+static void TileCountBounds(benchmark::State& state) {
+    std::size_t length = 0;
+    while (state.KeepRunning()) {
+        auto count = util::tileCount(sanFrancisco, 10);
+        length += count;
+    }
+}
+
+static void TileCoverPitchedViewport(benchmark::State& state) {
+    Transform transform;
+    transform.resize({ 512, 512 });
+    // slightly offset center so that tile order is better defined
+    transform.setLatLng({ 0.1, -0.1 });
+    transform.setZoom(8);
+    transform.setAngle(5.0);
+    transform.setPitch(40.0 * M_PI / 180.0);
+    
+    std::size_t length = 0;
+    while (state.KeepRunning()) {
+        auto tiles = util::tileCover(transform.getState(), 8);
+        length += tiles.size();
+    }
+}
+
+static void TileCoverBounds(benchmark::State& state) {
+    std::size_t length = 0;
+    while (state.KeepRunning()) {
+        auto tiles = util::tileCover(sanFrancisco, 8);
+        length += tiles.size();
+    }
+}
+
+static const auto geomPolygon = Polygon<double>{
+    {
+        {-122.5143814086914,37.779127216982424},
+        {-122.50811576843262,37.72721239056709},
+        {-122.50313758850099,37.70820178063929},
+        {-122.3938751220703,37.707454835665274},
+        {-122.37567901611328,37.70663997801684},
+        {-122.36297607421874,37.71343018466285},
+        {-122.354736328125,37.727280276860036},
+        {-122.36469268798828,37.73868429065797},
+        {-122.38014221191408,37.75442980295571},
+        {-122.38391876220702,37.78753873820529},
+        {-122.35919952392578,37.8065289741725},
+        {-122.35679626464844,37.820632846207864},
+        {-122.3712158203125,37.835276322922695},
+        {-122.3818588256836,37.82958198283902},
+        {-122.37190246582031,37.80788523279169},
+        {-122.38735198974608,37.791337175930686},
+        {-122.40966796874999,37.812767557570204},
+        {-122.46425628662108,37.807071480609274},
+        {-122.46803283691405,37.810326435534755},
+        {-122.47901916503906,37.81168262440736},
+        {-122.48966217041016,37.78916666399649},
+        {-122.50579833984375,37.78781006166096},
+        {-122.5143814086914,37.779127216982424}
+    }
+};
+
+static void TileCoverPolygon(benchmark::State& state) {
+    std::size_t length = 0;
+
+    while (state.KeepRunning()) {
+        auto tiles = util::tileCover(geomPolygon, 8);
+        length += tiles.size();
+    }
+}
+
+static void TileCountPolygon(benchmark::State& state) {
+    std::size_t length = 0;
+
+    while (state.KeepRunning()) {
+        auto tiles = util::tileCount(geomPolygon, 16);
+        length += tiles;
+    }
+}
+
+BENCHMARK(TileCountBounds);
+BENCHMARK(TileCountPolygon);
+BENCHMARK(TileCoverPitchedViewport);
+BENCHMARK(TileCoverBounds);
+BENCHMARK(TileCoverPolygon);
+