public void Test_VisitCells_QueryEdgeOnFaceBoundary()
{
int kIters = 100;
for (int iter = 0; iter < kIters; ++iter)
{
_logger.WriteLine("Iteration " + iter);
// Choose an edge AB such that B is nearly on the edge between two S2 cube
// faces, and such that the result of clipping AB to the face that nominally
// contains B (according to S2.GetFace) is empty when no padding is used.
int a_face, b_face;
S2Point a, b;
R2Point a_uv, b_uv;
do
{
a_face = S2Testing.Random.Uniform(6);
a = S2.FaceUVtoXYZ(a_face, S2Testing.Random.UniformDouble(-1, 1),
S2Testing.Random.UniformDouble(-1, 1)).Normalize();
b_face = S2.GetUVWFace(a_face, 0, 1); // Towards positive u-axis
var uTmp = 1 - S2Testing.Random.Uniform(2) * 0.5 * S2.DoubleEpsilon;
b = S2.FaceUVtoXYZ(b_face, uTmp, S2Testing.Random.UniformDouble(-1, 1)).Normalize();
} while (S2.GetFace(b) != b_face ||
S2EdgeClipping.ClipToFace(a, b, b_face, out a_uv, out b_uv));
// Verify that the clipping result is non-empty when a padding of
// S2EdgeClipping.kFaceClipErrorUVCoord is used instead.
Assert.True(S2EdgeClipping.ClipToPaddedFace(a, b, b_face, S2EdgeClipping.kFaceClipErrorUVCoord,
out a_uv, out b_uv));
// Create an S2ShapeIndex containing a single edge BC, where C is on the
// same S2 cube face as B (which is different than the face containing A).
S2Point c = S2.FaceUVtoXYZ(b_face, S2Testing.Random.UniformDouble(-1, 1),
S2Testing.Random.UniformDouble(-1, 1)).Normalize();
MutableS2ShapeIndex index = new();
index.Add(new S2Polyline.OwningShape(
new S2Polyline(new S2Point[] { b, c })));
// Check that the intersection between AB and BC is detected when the face
// containing BC is specified as a root cell. (Note that VisitCells()
// returns false only if the CellVisitor returns false, and otherwise
// returns true.)
S2CrossingEdgeQuery query = new(index);
S2PaddedCell root = new(S2CellId.FromFace(b_face), 0);
Assert.False(query.VisitCells(a, b, root, (S2ShapeIndexCell x) => false));
}
}
// Returns true if any edge of the indexed shape "clipped" intersects the
// cell "target". It may also return true if an edge is very close to
// "target"; the maximum error is less than 10 * S2Constants.DoubleEpsilon radians (about
// 15 nanometers).
private bool AnyEdgeIntersects(S2ClippedShape clipped, S2Cell target)
{
var bound = target.BoundUV.Expanded(kMaxError);
var face = target.Face;
var shape = Index().Shape(clipped.ShapeId);
int num_edges = clipped.NumEdges;
for (int i = 0; i < num_edges; ++i)
{
var edge = shape.GetEdge(clipped.Edge(i));
if (S2EdgeClipping.ClipToPaddedFace(edge.V0, edge.V1, face, kMaxError, out var p0, out var p1) &&
S2EdgeClipping.IntersectsRect(p0, p1, bound))
{
return(true);
}
}
return(false);
}