Merge pull request #796 from OskarLinde/offset_bugfix

Offset bug with delta < 1

src/GeometryEvaluator.cc

@@ -413,7 +413,7 @@ Response GeometryEvaluator::visit(State &state, const OffsetNode &node)
 				// ClipperLib documentation: The formula for the number of steps in a full
 				// circular arc is ... Pi / acos(1 - arc_tolerance / abs(delta))
 				double n = Calc::get_fragments_from_r(10, node.fn, node.fs, node.fa);
-				double arc_tolerance = abs(node.delta) * (1 - cos(M_PI / n));				
+				double arc_tolerance = std::abs(node.delta) * (1 - cos(M_PI / n));
 				const Polygon2d *result = ClipperUtils::applyOffset(*polygon, node.delta, node.join_type, node.miter_limit, arc_tolerance);
 				assert(result);
 				geom.reset(result);

testdata/scad/features/offset-tests.scad

@@ -34,6 +34,10 @@ offset(-4) shape1(-1, 0);
 shape1(0, 0);
 offset(4) shape1(1, 0);
 
-offset(delta = -5) shape1(-1, -1);
+offset(delta = -5) shape1(2, 1);
 shape1(0, -1);
 offset(delta = 5) shape1(1, -1);
+
+// Bug with fragment calculateion with delta < 1 due to abs() instead of std::abs()
+translate([-50,-50]) scale([25,25,1])
+	offset(delta = 0.9, join_type="round") square(.1);

tests/regression/dumptest/offset-tests-expected.csg

@@ -104,7 +104,7 @@ group() {
 	}
 	offset(delta = -5, join_type = miter, miter_limit = 2, $fn = 0, $fa = 12, $fs = 2) {
 		group() {
-			multmatrix([[1, 0, 0, -50], [0, 1, 0, -50], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+			multmatrix([[1, 0, 0, 100], [0, 1, 0, 50], [0, 0, 1, 0], [0, 0, 0, 1]]) {
 				difference() {
 					square(size = [30, 30], center = true);
 					square(size = [8, 8], center = true);
@@ -130,4 +130,11 @@ group() {
 			}
 		}
 	}
+	multmatrix([[1, 0, 0, -50], [0, 1, 0, -50], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+		multmatrix([[25, 0, 0, 0], [0, 25, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+			offset(delta = 0.9, join_type = round, miter_limit = 2, $fn = 0, $fa = 12, $fs = 2) {
+				square(size = [0.1, 0.1], center = false);
+			}
+		}
+	}
 }