private static S1ChordAngle GetMaxDistanceToEdgeBruteForce(S2Cell cell, S2Point a, S2Point b)
{
// If any antipodal endpoint is within the cell, the max distance is Pi.
if (cell.Contains(-a) || cell.Contains(-b))
{
return(S1ChordAngle.Straight);
}
S1ChordAngle max_dist = S1ChordAngle.Negative;
for (int i = 0; i < 4; ++i)
{
S2Point v0 = cell.Vertex(i);
S2Point v1 = cell.Vertex(i + 1);
// If the antipodal edge crosses through the cell, max distance is Pi.
if (S2.CrossingSign(-a, -b, v0, v1) >= 0)
{
return(S1ChordAngle.Straight);
}
S2.UpdateMaxDistance(a, v0, v1, ref max_dist);
S2.UpdateMaxDistance(b, v0, v1, ref max_dist);
S2.UpdateMaxDistance(v0, a, b, ref max_dist);
}
return(max_dist);
}
private static S1ChordAngle GetDistanceToPointBruteForce(S2Cell cell, S2Point target)
{
S1ChordAngle min_distance = S1ChordAngle.Infinity;
for (int i = 0; i < 4; ++i)
{
S2.UpdateMinDistance(target, cell.Vertex(i),
cell.Vertex(i + 1), ref min_distance);
}
return(min_distance);
}
public void Test_S2Cell_GetMaxDistanceToEdge()
{
// Test an edge for which its antipode crosses the cell. Validates both the
// standard and brute force implementations for this case.
S2Cell cell = S2Cell.FromFacePosLevel(0, 0, 20);
S2Point a = -S2.Interpolate(2.0, cell.Center(), cell.Vertex(0));
S2Point b = -S2.Interpolate(2.0, cell.Center(), cell.Vertex(2));
S1ChordAngle actual = cell.MaxDistance(a, b);
S1ChordAngle expected = GetMaxDistanceToEdgeBruteForce(cell, a, b);
Assert2.Near(expected.Radians(), S1ChordAngle.Straight.Radians(), S2.DoubleError);
Assert2.Near(actual.Radians(), S1ChordAngle.Straight.Radians(), S2.DoubleError);
}
private static S1ChordAngle GetMaxDistanceToPointBruteForce(S2Cell cell, S2Point target)
{
if (cell.Contains(-target))
{
return(S1ChordAngle.Straight);
}
S1ChordAngle max_distance = S1ChordAngle.Negative;
for (int i = 0; i < 4; ++i)
{
S2.UpdateMaxDistance(target, cell.Vertex(i),
cell.Vertex(i + 1), ref max_distance);
}
return(max_distance);
}
private static S1ChordAngle GetDistanceToEdgeBruteForce(S2Cell cell, S2Point a, S2Point b)
{
if (cell.Contains(a) || cell.Contains(b))
{
return(S1ChordAngle.Zero);
}
S1ChordAngle min_dist = S1ChordAngle.Infinity;
for (int i = 0; i < 4; ++i)
{
S2Point v0 = cell.Vertex(i);
S2Point v1 = cell.Vertex(i + 1);
// If the edge crosses through the cell, max distance is 0.
if (S2.CrossingSign(a, b, v0, v1) >= 0)
{
return(S1ChordAngle.Zero);
}
S2.UpdateMinDistance(a, v0, v1, ref min_dist);
S2.UpdateMinDistance(b, v0, v1, ref min_dist);
S2.UpdateMinDistance(v0, a, b, ref min_dist);
}
return(min_dist);
}
