Fix floating point error in the clip line to envelope logic

Author: breiler

ugs-platform/ugs-platform-plugin-designer/src/main/java/com/willwinder/ugs/nbp/designer/utils/GeometryUtils.java

@@ -25,7 +25,21 @@ public static LineString clipLineToEnvelope(LineString line, Envelope envelope)
         Coordinate p0 = line.getCoordinateN(0);
         Coordinate p1 = line.getCoordinateN(1);
 
-        Point2D[] clipped = liangBarskyClipLine(new Point2D.Double(p0.x, p0.y), new Point2D.Double(p1.x, p1.y), new Rectangle2D.Double(envelope.getMinX(), envelope.getMinY(), envelope.getWidth(), envelope.getHeight()));
+        // Allow for tiny floating-point overshoots like 251.00000000000003
+        final double epsilon = 1e-9;
+        Rectangle2D expandedEnvelope = new Rectangle2D.Double(
+                envelope.getMinX() - epsilon,
+                envelope.getMinY() - epsilon,
+                envelope.getWidth() + (2 * epsilon),
+                envelope.getHeight() + (2 * epsilon)
+        );
+
+        Point2D[] clipped = liangBarskyClipLine(
+                new Point2D.Double(p0.x, p0.y),
+                new Point2D.Double(p1.x, p1.y),
+                expandedEnvelope
+        );
+
         if (clipped == null) {
             return null;
         }
@@ -37,7 +51,6 @@ public static LineString clipLineToEnvelope(LineString line, Envelope envelope)
         return gf.createLineString(new Coordinate[]{start, end});
     }
 
-
     public static LineString generateLineString(Envelope envelope, double offsetAlongNormal, double angleInDegrees) {
         // Convert angle to radians
         double radians = Math.toRadians(-angleInDegrees);

ugs-platform/ugs-platform-plugin-designer/src/test/java/com/willwinder/ugs/nbp/designer/io/gcode/toolpaths/SurfaceToolPathTest.java

@@ -604,4 +604,36 @@ public void toGcodePathShouldAddSpindleSpeed() {
         assertEquals(9000, segment.getSpindleSpeed(), 0.01);
         assertEquals(200, segment.getFeedSpeed(), 0.01);
     }
+
+    @Test
+    public void toGcodePathShouldStartFromTheTopWithConventionalMilling() {
+        Rectangle rectangle = new Rectangle(0, 0);
+        rectangle.setSize(new Size(250, 270));
+        rectangle.setLeadInPercent(0);
+        rectangle.setDirection(Direction.CONVENTIONAL);
+        rectangle.setToolPathDirection(ToolPathDirection.HORIZONTAL);
+
+        Settings settings = new Settings();
+        settings.setToolDiameter(38);
+        settings.setToolStepOver(100);
+        settings.setSafeHeight(10);
+
+        SurfaceToolPath toolPath = new SurfaceToolPath(settings, rectangle);
+        toolPath.setStartDepth(1);
+        toolPath.setTargetDepth(1);
+
+        GcodePath gcodePath = toolPath.toGcodePath();
+        List<Segment> segments = gcodePath.getSegments();
+
+        // 8 passes -> 4 segments each, plus SEAM and final safe-height move
+        assertEquals(34, segments.size());
+
+        // Conventional milling should start at the top-most usable pass.
+        // Segment layout for the first pass:
+        // 0 SEAM, 1 safe Z, 2 XY start, 3 Z plunge, 4 line end
+        Segment firstPassStart = segments.get(2);
+        assertEquals(SegmentType.MOVE, firstPassStart.type);
+        assertXYPoint(firstPassStart.point, 19, 251);
+        assertFalse(firstPassStart.point.hasZ());
+    }
 }