diff --git a/src/geo/polygons.js b/src/geo/polygons.js
index d9b62c9f..1c3c62d7 100644
--- a/src/geo/polygons.js
+++ b/src/geo/polygons.js
@@ -18,7 +18,6 @@
         newPoint = BASE.newPoint;
 
     BASE.polygons = {
-        trace2count : trace2count,
         rayIntersect : rayIntersect,
         alignWindings : alignWindings,
         setWinding : setWinding,
@@ -548,60 +547,7 @@
             }
         }
 
-        return polys;
-    }
-
-    /**
-     * @param {Polygon} poly input
-     * @param {Polygon[]} traces output
-     * @param {number} offset distance to offset
-     * @param {number} count number of offsets
-     * @param {number} depth current depth (count) into offsets
-     * @param {Polygon[]} [last]
-     * @param {Polygon[]} [first]
-     */
-    function trace2count(poly, traces, offset, count, depth, last, first) {
-        if (count === 0) {
-            if (last) last.append(poly);
-            return;
-        }
-
-        // offset polygon to outer traces array
-        let calcoff = depth === 0 && last ? offset / 2 : offset,
-            outer = poly.offset(calcoff, []),
-            inner = [],
-            j;
-
-        // outer offset failed
-        if (outer.length === 0) {
-            if (last) last.append(poly);
-            return;
-        }
-
-        // offset poly children to inner traces array
-        if (poly.inner) {
-            poly.inner.forEach(function(ic) {
-                ic.offset(-calcoff, inner);
-            });
-        }
-
-        let newouter = [], newinner = [];
-        subtract(outer, inner, newouter, newinner, poly.getZ());
-
-        if (newouter.length > 0) {
-            traces.appendAll(newouter);
-            if (depth === 0 && first) {
-                first.appendAll(newouter);
-            }
-            // recurse for multiple shells
-            if (count > 0) {
-                for (j=0; j<newouter.length; j++) {
-                    trace2count(newouter[j], traces, offset, count - 1, depth + 1, last);
-                }
-            }
-        } else if (last) {
-            last.append(poly);
-        }
+        return opt.flat ? opt.outs : polys;
     }
 
     /**
diff --git a/src/kiri/slice.js b/src/kiri/slice.js
index b595a551..1817cc71 100644
--- a/src/kiri/slice.js
+++ b/src/kiri/slice.js
@@ -452,8 +452,7 @@
                     last = nulast;
                 }
                 last.forEach(function(inner) {
-                    // TODO replace with new offset() function
-                    POLY.trace2count(inner, top.inner, fillOffset, 1, 0);
+                    POLY.offset([inner], -fillOffset, {outs: top.inner, flat: true, z: slice.z});
                 });
             }
         });
@@ -1008,14 +1007,15 @@
 
         if (supports) supports.forEach(function (poly) {
             // angle based on width/height ratio
-            let angle = (poly.bounds.width() / poly.bounds.height() > 1) ? 90 : 0,
-                // calculate fill density
-                spacing = linewidth * (1 / density),
-                offsets = [];
-            // offset support poly for fill lines
-            POLY.trace2count(poly, offsets, linewidth/4, 1, 0);
+            let angle = (poly.bounds.width() / poly.bounds.height() > 1) ? 90 : 0;
+            // calculate fill density
+            let spacing = linewidth * (1 / density);
+            // inset support poly for fill lines 33% of nozzle width
+            let inset = POLY.offset([poly], -linewidth/3, {flat: true, z: slice.z});
             // do the fill
-            if (offsets.length > 0) fillArea(offsets, angle, spacing, poly.fills = []);
+            if (inset.length > 0) {
+                fillArea(inset, angle, spacing, poly.fills = []);
+            }
             return true;
         });
 
diff --git a/src/mode/fdm/driver.js b/src/mode/fdm/driver.js
index b01b9fd1..2af26b8b 100644
--- a/src/mode/fdm/driver.js
+++ b/src/mode/fdm/driver.js
@@ -669,7 +669,7 @@
 
                 // expand specified # of brims
                 brims.forEach(function(brim) {
-                    POLY.trace2count(brim, polys, -nozzle, process.outputBrimCount, 0);
+                    POLY.offset([brim], nozzle, {outs: polys, flat: true, count: process.outputBrimCount});
                 });
 
                 // output brim points