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Fix a line clipping edge case #92

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merged 1 commit into from
May 12, 2021
Merged

Fix a line clipping edge case #92

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18 changes: 12 additions & 6 deletions include/mapbox/geojsonvt/clip.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,7 @@ class clipper {
const auto& b = line[i + 1];
const double ak = get<I>(a);
const double bk = get<I>(b);
const bool isLastSeg = (i == (len - 2));

if (lineMetrics) segLen = ::hypot((b.x - a.x), (b.y - a.y));

Expand All @@ -135,9 +136,11 @@ class clipper {
t = calc_progress<I>(a, b, k1);
slice.emplace_back(intersect<I>(a, b, k1, t));
if (lineMetrics) slice.segStart = lineLen + segLen * t;
if (isLastSeg) slice.emplace_back(b); // last point

if (i == len - 2)
slice.emplace_back(b); // last point
} else if (bk == k1 && !isLastSeg) { // --->|.. |
if (lineMetrics) slice.segStart = lineLen + segLen;
slice.emplace_back(b);
}
} else if (ak > k2) {
if (bk < k1) { // <--|-----|---
Expand All @@ -152,13 +155,16 @@ class clipper {
slices.emplace_back(std::move(slice));

slice = newSlice(line);

} else if (bk < k2) { // | <--|---
t = calc_progress<I>(a, b, k2);
slice.emplace_back(intersect<I>(a, b, k2, t));
if (lineMetrics) slice.segStart = lineLen + segLen * t;
if (isLastSeg) slice.emplace_back(b); // last point

if (i == len - 2)
slice.emplace_back(b); // last point
} else if (bk == k2 && !isLastSeg) { // | ..|<---
if (lineMetrics) slice.segStart = lineLen + segLen;
slice.emplace_back(b);
}
} else {
slice.emplace_back(a);
Expand All @@ -177,7 +183,7 @@ class clipper {
slices.emplace_back(std::move(slice));
slice = newSlice(line);

} else if (i == len - 2) { // | --> |
} else if (isLastSeg) { // | --> |
slice.emplace_back(b);
}
}
Expand All @@ -186,7 +192,7 @@ class clipper {
}

if (!slice.empty()) { // add the final slice
slice.segEnd = lineLen;
if (lineMetrics) slice.segEnd = lineLen;
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slices.emplace_back(std::move(slice));
}
}
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38 changes: 38 additions & 0 deletions test/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -475,3 +475,41 @@ TEST(geoJSONToTile, Metrics) {
double rightClipEnd = (rightProps.find("mapbox_clip_end")->second).get<double>();
EXPECT_DOUBLE_EQ(rightClipEnd, 1.0);
}

TEST(GeoJSONVT, ClipVertexOnTileBorder) {
std::string data = R"geojson({
"type": "Feature",
"geometry": {
"type": "LineString",
"coordinates":[
[-77.031373697916663,38.895516493055553],
[-77.01416015625,38.887532552083336],
[-76.99,38.87]
]
}
})geojson"; // The second node is exactly on the (13, 2344, 3134) tile border.
auto geojson = mapbox::geojson::parse(data);
mapbox::geojsonvt::Options options;
options.lineMetrics = true;
options.buffer = 2048;
options.extent = 8192;

const double kEpsilon = 1e-5;

mapbox::geojsonvt::GeoJSONVT index{geojson,options};

const Tile& tile = index.getTile(13, 2344, 3134);
ASSERT_FALSE(tile.features.empty());
const mapbox::geometry::line_string<int16_t> expected{
{-2048, 2747}, {408, 5037}
};
const auto actual = tile.features[0].geometry.get<mapbox::geometry::line_string<int16_t>>();
ASSERT_EQ(actual, expected);

// Check line metrics
auto& props = tile.features[0].properties;
double clipStart1 = (props.find("mapbox_clip_start")->second).get<double>();
double clipEnd1 = (props.find("mapbox_clip_end")->second).get<double>();
EXPECT_NEAR(0.660622, clipStart1, kEpsilon);
EXPECT_NEAR(1.0, clipEnd1, kEpsilon);
}