1 files changed, 62 insertions, 0 deletions
diff --git a/src/mbgl/geometry/resample.cpp b/src/mbgl/geometry/resample.cpp
new file mode 100644
index 0000000000..abb3ef1e3c
--- /dev/null
+++ b/src/mbgl/geometry/resample.cpp
@@ -0,0 +1,62 @@
+#include <mbgl/geometry/resample.hpp>
+
+#include <mbgl/util/interpolate.hpp>
+
+#include <cmath>
+
+namespace mbgl {
+
+const float minScale = 0.5f;
+const std::array<std::vector<float>, 4> minScaleArrays = {{
+    /*1:*/ { minScale },
+    /*2:*/ { minScale, 2 },
+    /*4:*/ { minScale, 4, 2, 4 },
+    /*8:*/ { minScale, 8, 4, 8, 2, 8, 4, 8 }
+}};
+
+
+Anchors resample(const std::vector<Coordinate> &vertices, float spacing,
+                 const float /*minScale*/, float maxScale, const float tilePixelRatio,
+                 const int start) {
+
+    maxScale = std::round(std::fmax(std::fmin(8.0f, maxScale / 2.0f), 1.0f));
+    spacing *= tilePixelRatio / maxScale;
+    const size_t index = util::clamp<size_t>(std::floor(std::log(maxScale) / std::log(2)), 0, minScaleArrays.size() - 1);
+    const std::vector<float> &minScales = minScaleArrays[index];
+    const size_t len = minScales.size();
+
+    float distance = 0.0f;
+    float markedDistance = 0.0f;
+    int added = start;
+
+    Anchors points;
+
+    auto end = vertices.end() - 1;
+    int i = 0;
+    for (auto it = vertices.begin(); it != end; it++, i++) {
+        const Coordinate &a = *(it), b = *(it + 1);
+
+        float segmentDist = util::dist<float>(a, b);
+        float angle = util::angle_to(b, a);
+
+        while (markedDistance + spacing < distance + segmentDist) {
+            markedDistance += spacing;
+
+            float t = (markedDistance - distance) / segmentDist,
+                  x = util::interpolate(a.x, b.x, t),
+                  y = util::interpolate(a.y, b.y, t),
+                  s = minScales[added % len];
+
+            if (x >= 0 && x < 4096 && y >= 0 && y < 4096) {
+                points.emplace_back(x, y, angle, s, i);
+            }
+
+            added++;
+        }
+
+        distance += segmentDist;
+    }
+
+    return points;
+}
+}