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refactor(geometry): move maximal-rectangle search out of RemnantFinder

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The histogram search over a free/blocked cell grid never depended on the
obstacles being boxes. Move it to OpenNest.Core as MaximalRectangles.FromGrid
so other callers can build their own grids; RemnantFinder keeps building its
obstacle grid and calls it. No behavior change.
This commit is contained in:
aj committed 2026-10-01 07:28:13 -04:00
1 parent d14071692b
commit 694d4b28cc
2 files changed
+134 -102
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OpenNest.Engine/Fill/RemnantFinder.cs
+6 -102
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@@ -56,9 +56,12 @@ namespace OpenNest.Engine.Fill
if (grid.Rows <= 0 || grid.Cols <= 0)
return new List<Box>();
var merged = MergeCells(grid);
var sized = FilterBySize(merged, minDimension);
var unique = RemoveDominated(sized);
var unique = MaximalRectangles.FromGrid(
grid.XCoords,
grid.YCoords,
grid.Empty,
minDimension
);
SortByEdgeProximity(unique);
return unique;
}
@@ -188,56 +191,6 @@ namespace OpenNest.Engine.Fill
return false;
}
private static List<Box> FilterBySize(List<Box> boxes, double minDimension)
{
if (minDimension <= 0)
return boxes;
var result = new List<Box>();
foreach (var box in boxes)
{
if (box.Width >= minDimension && box.Length >= minDimension)
result.Add(box);
}
return result;
}
private static List<Box> RemoveDominated(List<Box> boxes)
{
boxes.Sort((a, b) => b.Area().CompareTo(a.Area()));
var results = new List<Box>();
foreach (var box in boxes)
{
var dominated = false;
foreach (var larger in results)
{
if (IsContainedIn(box, larger))
{
dominated = true;
break;
}
}
if (!dominated)
results.Add(box);
}
return results;
}
private static bool IsContainedIn(Box inner, Box outer)
{
var eps = Math.Tolerance.Epsilon;
return inner.Left >= outer.Left - eps
&& inner.Right <= outer.Right + eps
&& inner.Bottom >= outer.Bottom - eps
&& inner.Top <= outer.Top + eps;
}
private void SortByEdgeProximity(List<Box> boxes)
{
boxes.Sort(
@@ -451,54 +404,5 @@ namespace OpenNest.Engine.Fill
return new Box(left, bottom, right - left, top - bottom);
}
/// <summary>
/// Finds maximal empty rectangles using the histogram method.
/// For each row, builds a height histogram of consecutive empty cells
/// above, then extracts the largest rectangles from the histogram.
/// </summary>
private static List<Box> MergeCells(CellGrid grid)
{
var height = new int[grid.Rows, grid.Cols];
for (var c = 0; c < grid.Cols; c++)
{
for (var r = 0; r < grid.Rows; r++)
height[r, c] = grid.Empty[r, c] ? (r > 0 ? height[r - 1, c] + 1 : 1) : 0;
}
var candidates = new List<Box>();
for (var r = 0; r < grid.Rows; r++)
{
var stack = new Stack<(int startCol, int h)>();
for (var c = 0; c <= grid.Cols; c++)
{
var h = c < grid.Cols ? height[r, c] : 0;
var startCol = c;
while (stack.Count > 0 && stack.Peek().h > h)
{
var top = stack.Pop();
startCol = top.startCol;
candidates.Add(
new Box(
grid.XCoords[top.startCol],
grid.YCoords[r - top.h + 1],
grid.XCoords[c] - grid.XCoords[top.startCol],
grid.YCoords[r + 1] - grid.YCoords[r - top.h + 1]
)
);
}
if (h > 0)
stack.Push((startCol, h));
}
}
return candidates;
}
}
}