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Split bounding box along (0, 0) before reprojecting [WIP] [skip ci]

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(improves handling stereographic projections e.g epsg:3995)
This commit is contained in:
Artem Pavlenko 2024-07-26 14:28:41 +01:00
parent fc029ae5a5
commit 727e3a1ca7
1 changed files with 84 additions and 35 deletions
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119
src/proj_transform.cpp
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@ -42,7 +42,6 @@
#include <stdexcept> #include <stdexcept>
namespace mapnik { namespace mapnik {
namespace { // (local) namespace { // (local)
// Returns points in clockwise order. This allows us to do anti-meridian checks. // Returns points in clockwise order. This allows us to do anti-meridian checks.
@ -90,6 +89,36 @@ auto envelope_points(box2d<T> const& env, std::size_t num_points) -> geometry::m
return coords; return coords;
} }
std::vector<box2d<double>> split_bounding_box(box2d<double> const& bbox)
{
std::vector<box2d<double>> output;
if (bbox.minx() < 0 && bbox.maxx() > 0)
{
if (bbox.miny() < 0 && bbox.maxy() > 0)
{
output.emplace_back(bbox.minx(), bbox.miny(), 0, 0);
output.emplace_back(0, bbox.miny(), bbox.maxx(), 0);
output.emplace_back(0, 0, bbox.maxx(), bbox.maxy());
output.emplace_back(bbox.minx(), 0, 0, bbox.maxy());
}
else
{
output.emplace_back(bbox.minx(), bbox.miny(), 0, bbox.maxy());
output.emplace_back(0, bbox.miny(), bbox.maxx(), bbox.maxy());
}
}
else if (bbox.miny() < 0 && bbox.maxy() > 0)
{
output.emplace_back(bbox.minx(), bbox.miny(), bbox.maxx(), 0);
output.emplace_back(bbox.minx(), 0, bbox.maxx(), bbox.maxy());
}
else
{
output.push_back(bbox);
}
return output;
}
} // namespace } // namespace
proj_transform::proj_transform(projection const& source, projection const& dest) proj_transform::proj_transform(projection const& source, projection const& dest)
@ -398,7 +427,7 @@ bool proj_transform::backward(box2d<double>& box) const
} }
// More robust, but expensive, bbox transform // More robust, but expensive, bbox transform
// in the face of proj4 out of bounds conditions. // in the face of libproj out of bounds conditions.
// Can result in 20 -> 10 r/s performance hit. // Can result in 20 -> 10 r/s performance hit.
// Alternative is to provide proper clipping box // Alternative is to provide proper clipping box
// in the target srs by setting map 'maximum-extent' // in the target srs by setting map 'maximum-extent'
@ -413,27 +442,34 @@ bool proj_transform::backward(box2d<double>& env, std::size_t points) const
return backward(env); return backward(env);
} }
auto coords = envelope_points(env, points); // this is always clockwise
for (auto& p : coords)
{
double z = 0;
if (!backward(p.x, p.y, z))
return false;
}
box2d<double> result; box2d<double> result;
boost::geometry::envelope(coords, result); for (auto b : split_bounding_box(env))
if (is_source_longlat_ && !util::is_clockwise(coords))
{ {
// we've gone to a geographic CS, and our clockwise envelope has auto coords = envelope_points(b, points); // this is always clockwise
// changed into an anticlockwise one. This means we've crossed the antimeridian, and for (auto& p : coords)
// need to expand the X direction to +/-180 to include all the data. Once we can deal {
// with multiple bboxes in queries we can improve. double z = 0;
double miny = result.miny(); if (!backward(p.x, p.y, z))
result.expand_to_include(-180.0, miny); return false;
result.expand_to_include(180.0, miny); }
if (!result.valid())
boost::geometry::envelope(coords, result);
else
{
box2d<double> bb;
boost::geometry::envelope(coords, bb);
result.expand_to_include(bb);
}
if (is_source_longlat_ && !util::is_clockwise(coords))
{
// we've gone to a geographic CS, and our clockwise envelope has
// changed into an anticlockwise one. This means we've crossed the antimeridian, and
// need to expand the X direction to +/-180 to include all the data. Once we can deal
// with multiple bboxes in queries we can improve.
double miny = result.miny();
result.expand_to_include(-180.0, miny);
result.expand_to_include(180.0, miny);
}
} }
env.re_center(result.center().x, result.center().y); env.re_center(result.center().x, result.center().y);
@ -453,32 +489,45 @@ bool proj_transform::forward(box2d<double>& env, std::size_t points) const
} }
auto coords = envelope_points(env, points); // this is always clockwise auto coords = envelope_points(env, points); // this is always clockwise
double z = 0;
for (auto& p : coords) for (auto& p : coords)
{ {
double z = 0;
if (!forward(p.x, p.y, z)) if (!forward(p.x, p.y, z))
return false; return false;
} }
box2d<double> result; box2d<double> result;
boost::geometry::envelope(coords, result); for (auto b : split_bounding_box(env))
if (is_dest_longlat_ && !util::is_clockwise(coords))
{ {
// we've gone to a geographic CS, and our clockwise envelope has auto coords = envelope_points(b, points); // this is always clockwise
// changed into an anticlockwise one. This means we've crossed the antimeridian, and for (auto& p : coords)
// need to expand the X direction to +/-180 to include all the data. Once we can deal {
// with multiple bboxes in queries we can improve. double z = 0;
double miny = result.miny(); if (!forward(p.x, p.y, z))
result.expand_to_include(-180.0, miny); return false;
result.expand_to_include(180.0, miny); }
if (!result.valid())
boost::geometry::envelope(coords, result);
else
{
box2d<double> bb;
boost::geometry::envelope(coords, bb);
result.expand_to_include(bb);
}
if (is_dest_longlat_ && !util::is_clockwise(coords))
{
// we've gone to a geographic CS, and our clockwise envelope has
// changed into an anticlockwise one. This means we've crossed the antimeridian, and
// need to expand the X direction to +/-180 to include all the data. Once we can deal
// with multiple bboxes in queries we can improve.
double miny = result.miny();
result.expand_to_include(-180.0, miny);
result.expand_to_include(180.0, miny);
}
} }
env.re_center(result.center().x, result.center().y); env.re_center(result.center().x, result.center().y);
env.height(result.height()); env.height(result.height());
env.width(result.width()); env.width(result.width());
return true; return true;
} }