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fix: account for contour winding direction in lead-in normal computation

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ComputeNormal assumed CW winding for all contours. For CCW-wound cutouts,
line normals pointed to the material side instead of scrap, placing lead-ins
on the wrong side. Now accepts a winding parameter: lines flip the normal
for CCW winding, and arcs flip when arc direction differs from contour
winding (concave feature detection).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
AJ Isaacs
2026-04-02 12:06:08 -04:00
parent ec0baad585
commit 64945220b9
2 changed files with 20 additions and 13 deletions
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22
OpenNest.Core/CNC/CuttingStrategy/ContourCuttingStrategy.cs
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@@ -70,8 +70,8 @@ namespace OpenNest.CNC.CuttingStrategy
private void EmitContour(Program program, Shape shape, Vector point, Entity entity, ContourType? forceType = null)
{
var contourType = forceType ?? DetectContourType(shape);
var normal = ComputeNormal(point, entity, contourType);
var winding = DetermineWinding(shape);
var normal = ComputeNormal(point, entity, contourType, winding);
var leadIn = SelectLeadIn(contourType);
var leadOut = SelectLeadOut(contourType);
@@ -143,29 +143,33 @@ namespace OpenNest.CNC.CuttingStrategy
return ContourType.Internal;
}
public static double ComputeNormal(Vector point, Entity entity, ContourType contourType)
public static double ComputeNormal(Vector point, Entity entity, ContourType contourType,
RotationType winding = RotationType.CW)
{
double normal;
if (entity is Line line)
{
// Perpendicular to line direction
// Perpendicular to line direction: tangent + π/2 = left side.
// Left side = outward for CW winding; for CCW winding, outward
// is on the right side, so flip.
var tangent = line.EndPoint.AngleFrom(line.StartPoint);
normal = tangent + Math.Angle.HalfPI;
if (winding == RotationType.CCW)
normal += System.Math.PI;
}
else if (entity is Arc arc)
{
// Radial direction from center to point
// Radial direction from center to point.
// Flip when the arc direction differs from the contour winding —
// that indicates a concave feature where radial points inward.
normal = point.AngleFrom(arc.Center);
// For CCW arcs the radial points the wrong way — flip it.
// CW arcs are convex features (corners) where radial = outward.
// CCW arcs are concave features (slots) where radial = inward.
if (arc.Rotation == RotationType.CCW)
if (arc.Rotation != winding)
normal += System.Math.PI;
}
else if (entity is Circle circle)
{
// Radial outward — always correct regardless of winding
normal = point.AngleFrom(circle.Center);
}
else