copy ZM values to polygon in makeRegular

src/ol/geom/Polygon.js

@@ -434,6 +434,9 @@ export function makeRegular(polygon, center, radius, opt_angle) {
     const angle = startAngle + (modulo(i, sides) * 2 * Math.PI / sides);
     flatCoordinates[offset] = center[0] + (radius * Math.cos(angle));
     flatCoordinates[offset + 1] = center[1] + (radius * Math.sin(angle));
+    for (let j = 2; j < stride; j++) {
+      flatCoordinates[offset + j] = center[j];
+    }
   }
   polygon.changed();
 }

test/spec/ol/geom/polygon.test.js

@@ -605,6 +605,14 @@ describe('ol/geom/Polygon', function() {
       expect(coordinates[0][0]).to.roughlyEqual(0, 1e-9);
       expect(coordinates[0][1]).to.roughlyEqual(1, 1e-9);
     });
+
+    it('creates a regular polygon, maintaining ZM values', () => {
+      const circle = new Circle([0, 0, 1, 1], 1, 'XYZM');
+      const polygon = fromCircle(circle);
+      const coordinates = polygon.getLinearRing(0).getCoordinates();
+      expect(coordinates[0][2]).to.eql(1);
+      expect(coordinates[0][3]).to.eql(1);
+    });
   });
 
 });