diff --git a/src/geo/polygon.js b/src/geo/polygon.js
index 9c017514..ac13b4d9 100644
--- a/src/geo/polygon.js
+++ b/src/geo/polygon.js
@@ -287,7 +287,13 @@
             for (let i=0; i<pln; i++) {
                 const p = pa[(i+pln) % pln];
                 const d = ang[(i+pln) % pln];
-                if (d > 90) {
+                if (d > 179) {
+                    const s = slo[(i+pln) % pln];
+                    const pp = pa[(i+pln-1) % pln];
+                    const ps = slo[(i+pln-1) % pln];
+                    newp.push(p.follow(p.slopeTo(pp).normal(), 0.001));
+                    newp.push(p.follow(s.clone().normal().invert(), 0.001));
+                } else if (d > 90) {
                     const s = slo[(i+pln) % pln];
                     const pp = pa[(i+pln-1) % pln];
                     const ps = slo[(i+pln-1) % pln];
diff --git a/src/geo/slope.js b/src/geo/slope.js
index 517008d9..6187cdce 100644
--- a/src/geo/slope.js
+++ b/src/geo/slope.js
@@ -44,6 +44,10 @@
         return [this.dx, this.dy, this.angle].join(',');
     };
 
+    PRO.clone = function() {
+        return new Slope(null, null, this.dx, this.dy);
+    };
+
     /**
      * @param {Slope} s
      * @returns {boolean}
@@ -70,6 +74,13 @@
         return this;
     };
 
+    PRO.invert = function() {
+        this.dx = -this.dx;
+        this.dy = -this.dy;
+        this.angle = Math.atan2(this.dy, this.dx) * RAD2DEG;
+        return this;
+    }
+
     PRO.toUnit = function() {
         let max = Math.max(ABS(this.dx), ABS(this.dy));
         this.dx = this.dx / max;
diff --git a/src/mode/fdm/prepare.js b/src/mode/fdm/prepare.js
index 6710d352..927af606 100644
--- a/src/mode/fdm/prepare.js
+++ b/src/mode/fdm/prepare.js
@@ -491,8 +491,12 @@
                     if (lastOut.emit !== out.emit) {
                         heads.push({p1: lastOut.point, p2: out.point});
                     }
-                    const op = out.point, lp = lastOut.point,
-                        moved = (op.x !== lp.x) || (op.y !== lp.y) || (op.z !== lp.z);;
+                    const op = out.point, lp = lastOut.point;
+                    // const moved = Math.max(
+                    //     Math.abs(op.x - lp.x),
+                    //     Math.abs(op.y - lp.y),
+                    //     Math.abs(op.z - lp.z));
+                    // if (moved < 0.0001) return;
                     if (out.emit) {
                         if (!lastOut.emit || (ckspeed && out.speed !== lastOut.speed) || lastEnd) {
                             current = newPolygon().setOpen();