Files
OpenNest/OpenNest.Core/Geometry/SpatialQuery.cs
AJ Isaacs ebc1a5f980 refactor: extract shared helpers in SpatialQuery
Pull duplicated vertex collection, edge conversion, sorting, and
ray-circle solving into reusable private methods. Delegate the
no-offset DirectionalDistance overload to the offset version.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-08 00:15:30 -04:00

861 lines
32 KiB
C#

using OpenNest.Math;
using System.Collections.Generic;
using System.Linq;
namespace OpenNest.Geometry
{
public static class SpatialQuery
{
/// <summary>
/// Finds the distance from a vertex to a line segment along a push axis.
/// Returns double.MaxValue if the ray does not hit the segment.
/// </summary>
private static double RayEdgeDistance(Vector vertex, Line edge, PushDirection direction)
{
return RayEdgeDistance(
vertex.X, vertex.Y,
edge.pt1.X, edge.pt1.Y, edge.pt2.X, edge.pt2.Y,
direction);
}
[System.Runtime.CompilerServices.MethodImpl(
System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]
private static double RayEdgeDistance(
double vx, double vy,
double p1x, double p1y, double p2x, double p2y,
PushDirection direction)
{
switch (direction)
{
case PushDirection.Left:
case PushDirection.Right:
{
var dy = p2y - p1y;
if (System.Math.Abs(dy) < Tolerance.Epsilon)
return double.MaxValue;
var t = (vy - p1y) / dy;
if (t < -Tolerance.Epsilon || t > 1.0 + Tolerance.Epsilon)
return double.MaxValue;
var ix = p1x + t * (p2x - p1x);
var dist = direction == PushDirection.Left ? vx - ix : ix - vx;
if (dist > Tolerance.Epsilon) return dist;
if (dist >= -Tolerance.Epsilon) return 0;
return double.MaxValue;
}
case PushDirection.Down:
case PushDirection.Up:
{
var dx = p2x - p1x;
if (System.Math.Abs(dx) < Tolerance.Epsilon)
return double.MaxValue;
var t = (vx - p1x) / dx;
if (t < -Tolerance.Epsilon || t > 1.0 + Tolerance.Epsilon)
return double.MaxValue;
var iy = p1y + t * (p2y - p1y);
var dist = direction == PushDirection.Down ? vy - iy : iy - vy;
if (dist > Tolerance.Epsilon) return dist;
if (dist >= -Tolerance.Epsilon) return 0;
return double.MaxValue;
}
default:
return double.MaxValue;
}
}
/// <summary>
/// Generalized ray-edge distance along an arbitrary unit direction vector.
/// Returns double.MaxValue if the ray does not hit the segment.
/// </summary>
[System.Runtime.CompilerServices.MethodImpl(
System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]
public static double RayEdgeDistance(
double vx, double vy,
double p1x, double p1y, double p2x, double p2y,
double dirX, double dirY)
{
var ex = p2x - p1x;
var ey = p2y - p1y;
var det = ex * dirY - ey * dirX;
if (System.Math.Abs(det) < Tolerance.Epsilon)
return double.MaxValue;
var dvx = p1x - vx;
var dvy = p1y - vy;
var t = (ex * dvy - ey * dvx) / det;
if (t < -Tolerance.Epsilon)
return double.MaxValue;
var s = (dirX * dvy - dirY * dvx) / det;
if (s < -Tolerance.Epsilon || s > 1.0 + Tolerance.Epsilon)
return double.MaxValue;
if (t > Tolerance.Epsilon) return t;
if (t >= -Tolerance.Epsilon) return 0;
return double.MaxValue;
}
/// <summary>
/// Solves ray-circle intersection, returning the two parametric t values.
/// Returns false if no real intersection exists.
/// </summary>
[System.Runtime.CompilerServices.MethodImpl(
System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]
private static bool SolveRayCircle(
double vx, double vy,
double cx, double cy, double r,
double dirX, double dirY,
out double t1, out double t2)
{
var ox = vx - cx;
var oy = vy - cy;
var a = dirX * dirX + dirY * dirY;
var b = 2.0 * (ox * dirX + oy * dirY);
var c = ox * ox + oy * oy - r * r;
var discriminant = b * b - 4.0 * a * c;
if (discriminant < 0)
{
t1 = t2 = double.MaxValue;
return false;
}
var sqrtD = System.Math.Sqrt(discriminant);
var inv2a = 1.0 / (2.0 * a);
t1 = (-b - sqrtD) * inv2a;
t2 = (-b + sqrtD) * inv2a;
return true;
}
/// <summary>
/// Computes the distance from a point along a direction to an arc.
/// Solves ray-circle intersection, then constrains hits to the arc's
/// angular span. Returns double.MaxValue if no hit.
/// </summary>
[System.Runtime.CompilerServices.MethodImpl(
System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]
public static double RayArcDistance(
double vx, double vy,
double cx, double cy, double r,
double startAngle, double endAngle, bool reversed,
double dirX, double dirY)
{
if (!SolveRayCircle(vx, vy, cx, cy, r, dirX, dirY, out var t1, out var t2))
return double.MaxValue;
var best = double.MaxValue;
if (t1 > -Tolerance.Epsilon)
{
var hitAngle = Angle.NormalizeRad(System.Math.Atan2(
vy + t1 * dirY - cy, vx + t1 * dirX - cx));
if (Angle.IsBetweenRad(hitAngle, startAngle, endAngle, reversed))
best = t1 > Tolerance.Epsilon ? t1 : 0;
}
if (t2 > -Tolerance.Epsilon && t2 < best)
{
var hitAngle = Angle.NormalizeRad(System.Math.Atan2(
vy + t2 * dirY - cy, vx + t2 * dirX - cx));
if (Angle.IsBetweenRad(hitAngle, startAngle, endAngle, reversed))
best = t2 > Tolerance.Epsilon ? t2 : 0;
}
return best;
}
/// <summary>
/// Computes the distance from a point along a direction to a full circle.
/// Returns double.MaxValue if no hit.
/// </summary>
[System.Runtime.CompilerServices.MethodImpl(
System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]
public static double RayCircleDistance(
double vx, double vy,
double cx, double cy, double r,
double dirX, double dirY)
{
if (!SolveRayCircle(vx, vy, cx, cy, r, dirX, dirY, out var t1, out var t2))
return double.MaxValue;
if (t1 > Tolerance.Epsilon) return t1;
if (t1 >= -Tolerance.Epsilon) return 0;
if (t2 > Tolerance.Epsilon) return t2;
if (t2 >= -Tolerance.Epsilon) return 0;
return double.MaxValue;
}
/// <summary>
/// Computes the minimum translation distance along a push direction before
/// any edge of movingLines contacts any edge of stationaryLines.
/// Returns double.MaxValue if no collision path exists.
/// </summary>
public static double DirectionalDistance(List<Line> movingLines, List<Line> stationaryLines, PushDirection direction)
{
return DirectionalDistance(movingLines, 0, 0, stationaryLines, direction);
}
/// <summary>
/// Computes the minimum directional distance with the moving lines translated
/// by (movingDx, movingDy) without creating new Line objects.
/// </summary>
public static double DirectionalDistance(
List<Line> movingLines, double movingDx, double movingDy,
List<Line> stationaryLines, PushDirection direction)
{
var minDist = double.MaxValue;
var movingOffset = new Vector(movingDx, movingDy);
// Case 1: Each moving vertex -> each stationary edge
var movingVertices = CollectVertices(movingLines, movingOffset);
var stationaryEdges = ToEdgeArray(stationaryLines);
SortEdgesForPruning(stationaryEdges, direction);
foreach (var mv in movingVertices)
{
var d = OneWayDistance(mv, stationaryEdges, Vector.Zero, direction);
if (d < minDist) minDist = d;
}
// Case 2: Each stationary vertex -> each moving edge (opposite direction)
var opposite = OppositeDirection(direction);
var stationaryVertices = CollectVertices(stationaryLines, Vector.Zero);
var movingEdges = ToEdgeArray(movingLines);
SortEdgesForPruning(movingEdges, opposite);
foreach (var sv in stationaryVertices)
{
var d = OneWayDistance(sv, movingEdges, movingOffset, opposite);
if (d < minDist) minDist = d;
}
return minDist;
}
/// <summary>
/// Packs line segments into a flat double array [x1,y1,x2,y2, ...] for GPU transfer.
/// </summary>
public static double[] FlattenLines(List<Line> lines)
{
var result = new double[lines.Count * 4];
for (int i = 0; i < lines.Count; i++)
{
var line = lines[i];
result[i * 4] = line.pt1.X;
result[i * 4 + 1] = line.pt1.Y;
result[i * 4 + 2] = line.pt2.X;
result[i * 4 + 3] = line.pt2.Y;
}
return result;
}
/// <summary>
/// Computes the minimum directional distance using raw edge arrays and location offsets
/// to avoid all intermediate object allocations.
/// </summary>
public static double DirectionalDistance(
(Vector start, Vector end)[] movingEdges, Vector movingOffset,
(Vector start, Vector end)[] stationaryEdges, Vector stationaryOffset,
PushDirection direction)
{
var minDist = double.MaxValue;
SortEdgesForPruning(stationaryEdges, direction);
// Case 1: Each moving vertex -> each stationary edge
var movingVertices = CollectVertices(movingEdges, movingOffset);
foreach (var mv in movingVertices)
{
var d = OneWayDistance(mv, stationaryEdges, stationaryOffset, direction);
if (d < minDist) minDist = d;
}
// Case 2: Each stationary vertex -> each moving edge (opposite direction)
var opposite = OppositeDirection(direction);
SortEdgesForPruning(movingEdges, opposite);
var stationaryVertices = CollectVertices(stationaryEdges, stationaryOffset);
foreach (var sv in stationaryVertices)
{
var d = OneWayDistance(sv, movingEdges, movingOffset, opposite);
if (d < minDist) minDist = d;
}
return minDist;
}
public static double OneWayDistance(
Vector vertex, (Vector start, Vector end)[] edges, Vector edgeOffset,
PushDirection direction)
{
var minDist = double.MaxValue;
var vx = vertex.X;
var vy = vertex.Y;
// Pruning: edges are sorted by their perpendicular min-coordinate in PartBoundary.
if (direction == PushDirection.Left || direction == PushDirection.Right)
{
for (var i = 0; i < edges.Length; i++)
{
var e1 = edges[i].start + edgeOffset;
var e2 = edges[i].end + edgeOffset;
var minY = e1.Y < e2.Y ? e1.Y : e2.Y;
var maxY = e1.Y > e2.Y ? e1.Y : e2.Y;
// Since edges are sorted by minY, if vy < minY, then vy < all subsequent minY.
if (vy < minY - Tolerance.Epsilon)
break;
if (vy > maxY + Tolerance.Epsilon)
continue;
var d = RayEdgeDistance(vx, vy, e1.X, e1.Y, e2.X, e2.Y, direction);
if (d < minDist) minDist = d;
}
}
else // Up/Down
{
for (var i = 0; i < edges.Length; i++)
{
var e1 = edges[i].start + edgeOffset;
var e2 = edges[i].end + edgeOffset;
var minX = e1.X < e2.X ? e1.X : e2.X;
var maxX = e1.X > e2.X ? e1.X : e2.X;
// Since edges are sorted by minX, if vx < minX, then vx < all subsequent minX.
if (vx < minX - Tolerance.Epsilon)
break;
if (vx > maxX + Tolerance.Epsilon)
continue;
var d = RayEdgeDistance(vx, vy, e1.X, e1.Y, e2.X, e2.Y, direction);
if (d < minDist) minDist = d;
}
}
return minDist;
}
public static PushDirection OppositeDirection(PushDirection direction)
{
switch (direction)
{
case PushDirection.Left: return PushDirection.Right;
case PushDirection.Right: return PushDirection.Left;
case PushDirection.Up: return PushDirection.Down;
case PushDirection.Down: return PushDirection.Up;
default: return direction;
}
}
public static bool IsHorizontalDirection(PushDirection direction)
{
return direction is PushDirection.Left or PushDirection.Right;
}
public static double EdgeDistance(Box box, Box boundary, PushDirection direction)
{
switch (direction)
{
case PushDirection.Left: return box.Left - boundary.Left;
case PushDirection.Right: return boundary.Right - box.Right;
case PushDirection.Up: return boundary.Top - box.Top;
case PushDirection.Down: return box.Bottom - boundary.Bottom;
default: return double.MaxValue;
}
}
public static Vector DirectionToOffset(PushDirection direction, double distance)
{
switch (direction)
{
case PushDirection.Left: return new Vector(-distance, 0);
case PushDirection.Right: return new Vector(distance, 0);
case PushDirection.Up: return new Vector(0, distance);
case PushDirection.Down: return new Vector(0, -distance);
default: return new Vector();
}
}
public static double DirectionalGap(Box from, Box to, PushDirection direction)
{
switch (direction)
{
case PushDirection.Left: return from.Left - to.Right;
case PushDirection.Right: return to.Left - from.Right;
case PushDirection.Up: return to.Bottom - from.Top;
case PushDirection.Down: return from.Bottom - to.Top;
default: return double.MaxValue;
}
}
#region Generalized direction (Vector) overloads
/// <summary>
/// Computes how far a box can travel along the given unit direction
/// before exiting the boundary box.
/// </summary>
public static double EdgeDistance(Box box, Box boundary, Vector direction)
{
var dist = double.MaxValue;
if (direction.X < -Tolerance.Epsilon)
{
var d = (box.Left - boundary.Left) / -direction.X;
if (d < dist) dist = d;
}
else if (direction.X > Tolerance.Epsilon)
{
var d = (boundary.Right - box.Right) / direction.X;
if (d < dist) dist = d;
}
if (direction.Y < -Tolerance.Epsilon)
{
var d = (box.Bottom - boundary.Bottom) / -direction.Y;
if (d < dist) dist = d;
}
else if (direction.Y > Tolerance.Epsilon)
{
var d = (boundary.Top - box.Top) / direction.Y;
if (d < dist) dist = d;
}
return dist < 0 ? 0 : dist;
}
/// <summary>
/// Computes the directional gap between two boxes along an arbitrary unit direction.
/// Positive means 'to' is ahead of 'from' in the push direction.
/// </summary>
public static double DirectionalGap(Box from, Box to, Vector direction)
{
var fromMax = BoxProjectionMax(from, direction.X, direction.Y);
var toMin = BoxProjectionMin(to, direction.X, direction.Y);
return toMin - fromMax;
}
/// <summary>
/// Returns true if two boxes overlap when projected onto the axis
/// perpendicular to the given unit direction.
/// </summary>
public static bool PerpendicularOverlap(Box a, Box b, Vector direction)
{
var px = -direction.Y;
var py = direction.X;
var aMin = BoxProjectionMin(a, px, py);
var aMax = BoxProjectionMax(a, px, py);
var bMin = BoxProjectionMin(b, px, py);
var bMax = BoxProjectionMax(b, px, py);
return aMin <= bMax + Tolerance.Epsilon && bMin <= aMax + Tolerance.Epsilon;
}
/// <summary>
/// Computes the minimum translation distance along an arbitrary unit direction
/// before any edge of movingLines contacts any edge of stationaryLines.
/// </summary>
public static double DirectionalDistance(List<Line> movingLines, List<Line> stationaryLines, Vector direction)
{
var minDist = double.MaxValue;
var dirX = direction.X;
var dirY = direction.Y;
var movingVertices = CollectVertices(movingLines, Vector.Zero);
foreach (var mv in movingVertices)
{
for (var i = 0; i < stationaryLines.Count; i++)
{
var e = stationaryLines[i];
var d = RayEdgeDistance(mv.X, mv.Y, e.pt1.X, e.pt1.Y, e.pt2.X, e.pt2.Y, dirX, dirY);
if (d < minDist) minDist = d;
}
}
var oppX = -dirX;
var oppY = -dirY;
var stationaryVertices = CollectVertices(stationaryLines, Vector.Zero);
foreach (var sv in stationaryVertices)
{
for (var i = 0; i < movingLines.Count; i++)
{
var e = movingLines[i];
var d = RayEdgeDistance(sv.X, sv.Y, e.pt1.X, e.pt1.Y, e.pt2.X, e.pt2.Y, oppX, oppY);
if (d < minDist) minDist = d;
}
}
return minDist;
}
/// <summary>
/// Computes the minimum translation distance along an arbitrary unit direction
/// before any vertex/edge of movingEntities contacts any vertex/edge of
/// stationaryEntities. Works with native Line, Arc, and Circle entities
/// without tessellation.
/// </summary>
public static double DirectionalDistance(
List<Entity> movingEntities, List<Entity> stationaryEntities, Vector direction)
{
var minDist = double.MaxValue;
var dirX = direction.X;
var dirY = direction.Y;
var movingVertices = ExtractEntityVertices(movingEntities);
for (var v = 0; v < movingVertices.Length; v++)
{
var vx = movingVertices[v].X;
var vy = movingVertices[v].Y;
for (var j = 0; j < stationaryEntities.Count; j++)
{
var d = RayEntityDistance(vx, vy, stationaryEntities[j], dirX, dirY);
if (d < minDist)
{
minDist = d;
if (d <= 0) return 0;
}
}
}
var oppX = -dirX;
var oppY = -dirY;
var stationaryVertices = ExtractEntityVertices(stationaryEntities);
for (var v = 0; v < stationaryVertices.Length; v++)
{
var vx = stationaryVertices[v].X;
var vy = stationaryVertices[v].Y;
for (var j = 0; j < movingEntities.Count; j++)
{
var d = RayEntityDistance(vx, vy, movingEntities[j], oppX, oppY);
if (d < minDist)
{
minDist = d;
if (d <= 0) return 0;
}
}
}
// Phase 3: Curve-to-curve direct distance.
// The vertex-to-entity approach misses the closest contact between two
// curved entities (circles/arcs) because only a few cardinal vertices are
// sampled. The true closest contact along the push direction is found by
// treating it as a ray from one center to an expanded circle at the other
// center (radius = r1 + r2).
for (var i = 0; i < movingEntities.Count; i++)
{
var me = movingEntities[i];
if (!TryGetCurveParams(me, out var mcx, out var mcy, out var mr))
continue;
for (var j = 0; j < stationaryEntities.Count; j++)
{
var se = stationaryEntities[j];
if (!TryGetCurveParams(se, out var scx, out var scy, out var sr))
continue;
var d = RayCircleDistance(mcx, mcy, scx, scy, mr + sr, dirX, dirY);
if (d >= minDist || d == double.MaxValue)
continue;
// For arcs, verify the contact point falls within both arcs' angular ranges.
if (me is Arc || se is Arc)
{
var mx = mcx + d * dirX;
var my = mcy + d * dirY;
var toCx = scx - mx;
var toCy = scy - my;
if (me is Arc mArc)
{
var angle = Angle.NormalizeRad(System.Math.Atan2(toCy, toCx));
if (!Angle.IsBetweenRad(angle, mArc.StartAngle, mArc.EndAngle, mArc.IsReversed))
continue;
}
if (se is Arc sArc)
{
var angle = Angle.NormalizeRad(System.Math.Atan2(-toCy, -toCx));
if (!Angle.IsBetweenRad(angle, sArc.StartAngle, sArc.EndAngle, sArc.IsReversed))
continue;
}
}
minDist = d;
if (d <= 0) return 0;
}
}
return minDist;
}
private static double RayEntityDistance(
double vx, double vy, Entity entity, double dirX, double dirY)
{
if (entity is Line line)
{
return RayEdgeDistance(vx, vy,
line.pt1.X, line.pt1.Y, line.pt2.X, line.pt2.Y,
dirX, dirY);
}
if (entity is Arc arc)
{
return RayArcDistance(vx, vy,
arc.Center.X, arc.Center.Y, arc.Radius,
arc.StartAngle, arc.EndAngle, arc.IsReversed,
dirX, dirY);
}
if (entity is Circle circle)
{
return RayCircleDistance(vx, vy,
circle.Center.X, circle.Center.Y, circle.Radius,
dirX, dirY);
}
return double.MaxValue;
}
private static Vector[] ExtractEntityVertices(List<Entity> entities)
{
var vertices = new HashSet<Vector>();
for (var i = 0; i < entities.Count; i++)
{
var entity = entities[i];
if (entity is Line line)
{
vertices.Add(line.pt1);
vertices.Add(line.pt2);
}
else if (entity is Arc arc)
{
vertices.Add(arc.StartPoint());
vertices.Add(arc.EndPoint());
AddArcExtremeVertices(vertices, arc);
}
else if (entity is Circle circle)
{
vertices.Add(new Vector(circle.Center.X + circle.Radius, circle.Center.Y));
vertices.Add(new Vector(circle.Center.X - circle.Radius, circle.Center.Y));
vertices.Add(new Vector(circle.Center.X, circle.Center.Y + circle.Radius));
vertices.Add(new Vector(circle.Center.X, circle.Center.Y - circle.Radius));
}
}
return vertices.ToArray();
}
private static void AddArcExtremeVertices(HashSet<Vector> points, Arc arc)
{
var a1 = arc.StartAngle;
var a2 = arc.EndAngle;
if (arc.IsReversed)
Generic.Swap(ref a1, ref a2);
if (Angle.IsBetweenRad(Angle.TwoPI, a1, a2))
points.Add(new Vector(arc.Center.X + arc.Radius, arc.Center.Y));
if (Angle.IsBetweenRad(Angle.HalfPI, a1, a2))
points.Add(new Vector(arc.Center.X, arc.Center.Y + arc.Radius));
if (Angle.IsBetweenRad(System.Math.PI, a1, a2))
points.Add(new Vector(arc.Center.X - arc.Radius, arc.Center.Y));
if (Angle.IsBetweenRad(System.Math.PI * 1.5, a1, a2))
points.Add(new Vector(arc.Center.X, arc.Center.Y - arc.Radius));
}
private static HashSet<Vector> CollectVertices(List<Line> lines, Vector offset)
{
var vertices = new HashSet<Vector>();
for (var i = 0; i < lines.Count; i++)
{
vertices.Add(lines[i].pt1 + offset);
vertices.Add(lines[i].pt2 + offset);
}
return vertices;
}
private static HashSet<Vector> CollectVertices((Vector start, Vector end)[] edges, Vector offset)
{
var vertices = new HashSet<Vector>();
for (var i = 0; i < edges.Length; i++)
{
vertices.Add(edges[i].start + offset);
vertices.Add(edges[i].end + offset);
}
return vertices;
}
private static (Vector start, Vector end)[] ToEdgeArray(List<Line> lines)
{
var edges = new (Vector start, Vector end)[lines.Count];
for (var i = 0; i < lines.Count; i++)
edges[i] = (lines[i].pt1, lines[i].pt2);
return edges;
}
private static void SortEdgesForPruning((Vector start, Vector end)[] edges, PushDirection direction)
{
if (direction == PushDirection.Left || direction == PushDirection.Right)
System.Array.Sort(edges, (a, b) =>
System.Math.Min(a.start.Y, a.end.Y).CompareTo(System.Math.Min(b.start.Y, b.end.Y)));
else
System.Array.Sort(edges, (a, b) =>
System.Math.Min(a.start.X, a.end.X).CompareTo(System.Math.Min(b.start.X, b.end.X)));
}
private static bool TryGetCurveParams(Entity entity, out double cx, out double cy, out double r)
{
if (entity is Circle circle)
{
cx = circle.Center.X; cy = circle.Center.Y; r = circle.Radius;
return true;
}
if (entity is Arc arc)
{
cx = arc.Center.X; cy = arc.Center.Y; r = arc.Radius;
return true;
}
cx = cy = r = 0;
return false;
}
private static double BoxProjectionMin(Box box, double dx, double dy)
{
var x = dx >= 0 ? box.Left : box.Right;
var y = dy >= 0 ? box.Bottom : box.Top;
return x * dx + y * dy;
}
private static double BoxProjectionMax(Box box, double dx, double dy)
{
var x = dx >= 0 ? box.Right : box.Left;
var y = dy >= 0 ? box.Top : box.Bottom;
return x * dx + y * dy;
}
#endregion
public static Box GetLargestBoxVertically(Vector pt, Box bounds, IEnumerable<Box> boxes)
{
var verticalBoxes = boxes.Where(b => !(b.Left > pt.X || b.Right < pt.X)).ToList();
if (!FindVerticalLimits(pt, bounds, verticalBoxes, out var top, out var btm))
return Box.Empty;
var horizontalBoxes = boxes.Where(b => !(b.Bottom >= top || b.Top <= btm)).ToList();
if (!FindHorizontalLimits(pt, bounds, horizontalBoxes, out var lft, out var rgt))
return Box.Empty;
return new Box(lft, btm, rgt - lft, top - btm);
}
public static Box GetLargestBoxHorizontally(Vector pt, Box bounds, IEnumerable<Box> boxes)
{
var horizontalBoxes = boxes.Where(b => !(b.Bottom > pt.Y || b.Top < pt.Y)).ToList();
if (!FindHorizontalLimits(pt, bounds, horizontalBoxes, out var lft, out var rgt))
return Box.Empty;
var verticalBoxes = boxes.Where(b => !(b.Left >= rgt || b.Right <= lft)).ToList();
if (!FindVerticalLimits(pt, bounds, verticalBoxes, out var top, out var btm))
return Box.Empty;
return new Box(lft, btm, rgt - lft, top - btm);
}
private static bool FindVerticalLimits(Vector pt, Box bounds, List<Box> boxes, out double top, out double btm)
{
top = double.MaxValue;
btm = double.MinValue;
foreach (var box in boxes)
{
var boxBtm = box.Bottom;
var boxTop = box.Top;
if (boxBtm > pt.Y && boxBtm < top)
top = boxBtm;
else if (box.Top < pt.Y && boxTop > btm)
btm = boxTop;
}
if (top == double.MaxValue)
{
if (bounds.Top > pt.Y) top = bounds.Top;
else return false;
}
if (btm == double.MinValue)
{
if (bounds.Bottom < pt.Y) btm = bounds.Bottom;
else return false;
}
return true;
}
private static bool FindHorizontalLimits(Vector pt, Box bounds, List<Box> boxes, out double lft, out double rgt)
{
lft = double.MinValue;
rgt = double.MaxValue;
foreach (var box in boxes)
{
var boxLft = box.Left;
var boxRgt = box.Right;
if (boxLft > pt.X && boxLft < rgt)
rgt = boxLft;
else if (boxRgt < pt.X && boxRgt > lft)
lft = boxRgt;
}
if (rgt == double.MaxValue)
{
if (bounds.Right > pt.X) rgt = bounds.Right;
else return false;
}
if (lft == double.MinValue)
{
if (bounds.Left < pt.X) lft = bounds.Left;
else return false;
}
return true;
}
}
}