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Use error bound filter in isInCircle predicate instead of long double. #1162

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Use error bound filter in isInCircle predicate instead of long double. #1162

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66 changes: 53 additions & 13 deletions src/triangulate/quadedge/TrianglePredicate.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -29,16 +29,30 @@ namespace quadedge {

geom::Location
TrianglePredicate::isInCircleNonRobust(
const CoordinateXY& a, const CoordinateXY& b, const CoordinateXY& c,
const CoordinateXY& p)
const CoordinateXY& p, const CoordinateXY& q, const CoordinateXY& r,
const CoordinateXY& t)
{
auto det =
(a.x * a.x + a.y * a.y) * triArea(b, c, p)
- (b.x * b.x + b.y * b.y) * triArea(a, c, p)
+ (c.x * c.x + c.y * c.y) * triArea(a, b, p)
- (p.x * p.x + p.y * p.y) * triArea(a, b, c);

return det > 0 ? geom::Location::EXTERIOR : (det < 0 ? geom::Location::INTERIOR : geom::Location::BOUNDARY);
auto qpx = q.x - p.x;
auto qpy = q.y - p.y;
auto rpx = r.x - p.x;
auto rpy = r.y - p.y;
auto tpx = t.x - p.x;
auto tpy = t.y - p.y;
auto tqx = t.x - q.x;
auto tqy = t.y - q.y;
auto rqx = r.x - q.x;
auto rqy = r.y - q.y;
auto qpxtpy = qpx * tpy;
auto qpytpx = qpy * tpx;
auto tpxtqx = tpx * tqx;
auto tpytqy = tpy * tqy;
auto qpxrpy = qpx * rpy;
auto qpyrpx = qpy * rpx;
auto rpxrqx = rpx * rqx;
auto rpyrqy = rpy * rqy;
auto det = (qpxtpy - qpytpx) * (rpxrqx + rpyrqy)
- (qpxrpy - qpyrpx) * (tpxtqx + tpytqy);
return static_cast<geom::Location>( (det > 0) - (det < 0) + 1 );
}

geom::Location
Expand Down Expand Up @@ -91,11 +105,37 @@ TrianglePredicate::triArea(const CoordinateXY& a,

geom::Location
TrianglePredicate::isInCircleRobust(
const CoordinateXY& a, const CoordinateXY& b, const CoordinateXY& c,
const CoordinateXY& p)
const CoordinateXY& q, const CoordinateXY& p, const CoordinateXY& r,
const CoordinateXY& t)
{
// This implementation is not robust, name is ported from JTS.
return isInCircleNormalized(a, b, c, p);
// This implementation is not robust and defaults to BOUNDARY in case of
// uncertainty.
auto qpx = q.x - p.x;
auto qpy = q.y - p.y;
auto rpx = r.x - p.x;
auto rpy = r.y - p.y;
auto tpx = t.x - p.x;
auto tpy = t.y - p.y;
auto tqx = t.x - q.x;
auto tqy = t.y - q.y;
auto rqx = r.x - q.x;
auto rqy = r.y - q.y;
auto qpxtpy = qpx * tpy;
auto qpytpx = qpy * tpx;
auto tpxtqx = tpx * tqx;
auto tpytqy = tpy * tqy;
auto qpxrpy = qpx * rpy;
auto qpyrpx = qpy * rpx;
auto rpxrqx = rpx * rqx;
auto rpyrqy = rpy * rqy;
auto det = (qpxtpy - qpytpx) * (rpxrqx + rpyrqy)
- (qpxrpy - qpyrpx) * (tpxtqx + tpytqy);
auto deterror = ((std::abs(qpxtpy) + std::abs(qpytpx))
* (std::abs(rpxrqx) + std::abs(rpyrqy))
+ (std::abs(qpxrpy) + std::abs(qpyrpx))
* (std::abs(tpxtqx) + std::abs(tpytqy)))
* 9.99200719823023e-16;
return static_cast<geom::Location>( (det > deterror) - (det < -deterror) + 1 );
}

} // namespace geos.triangulate.quadedge
Expand Down
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