diff --git a/release.md b/release.md
index 9c002ea7..9d9ce01c 100644
--- a/release.md
+++ b/release.md
@@ -17,13 +17,14 @@ Full docs @ https://docs.grid.space/projects/kiri-moto
 
 * added batch processing to object adds/removes to speedup complex workspace restore
 * substitute some prusa slicer [variables] with KM {variables} on import
-* fix CAM output order for tool changes an spindle speed updates
-* add CAM pocket operation using surface selection
+* fix CNC output order for tool changes an spindle speed updates
+* add CNC pocket operation using surface selection
 * fix dog-bones on outlines cut by tabs
 * skip pockets that resolve to null
-* fix cnc contour path collision
+* fix CNC contour path collision
 * 10x speedup for true shadow generation
-* add gcode feature macros for fdm transitions
+* add FDM gcode feature macros for transitions
+* add FDM option to alternate shell winding direction
 
 ## Mesh:Tool (1.2.0)
 
diff --git a/src/kiri-mode/fdm/client.js b/src/kiri-mode/fdm/client.js
index 5114e8b5..de32b8d5 100644
--- a/src/kiri-mode/fdm/client.js
+++ b/src/kiri-mode/fdm/client.js
@@ -54,6 +54,7 @@ FDM.init = function(kiri, api) {
         "outputFillMult": LANG.ou_flml_s,
         "outputSparseMult": LANG.ou_spml_s,
         "outputRetractWipe": LANG.ad_wpln_s,
+        "outputAlternating": LANG.ad_altr_s,
         "outputShortPoly": LANG.ad_spol_s,
         "outputMinSpeed": LANG.ad_mins_s,
         "outputCoastDist": LANG.ad_scst_s,
diff --git a/src/kiri-mode/fdm/prepare.js b/src/kiri-mode/fdm/prepare.js
index 3310c60d..bc73bed4 100644
--- a/src/kiri-mode/fdm/prepare.js
+++ b/src/kiri-mode/fdm/prepare.js
@@ -1041,6 +1041,7 @@ function slicePrintPath(print, slice, startPoint, offset, output, opt = {}) {
         } else {
             let finishShell = poly.depth === 0 && !firstLayer;
             startPoint = print.polyPrintPath(poly, startPoint, preout, {
+                ccw: opt.shell && process.outputAlternating && slice.index % 2,
                 tool: extruder,
                 rate: finishShell ? finishSpeed : printSpeed,
                 accel: finishShell,
@@ -1387,14 +1388,22 @@ function slicePrintPath(print, slice, startPoint, offset, output, opt = {}) {
 
             // innermost shells
             let inner = next.innerShells() || [];
+            let shells = next.shells || [];
+
+            // alternating winding option
+            // if (process.outputAlternating || slice.index % 2) {
+            //     console.log({alternating: slice, shells, inner});
+            //     POLY.setWinding(inner, false);
+            //     POLY.setWinding(shells, false);
+            // }
 
             // output inner polygons
-            if (shellOrder === 1) outputTraces(inner, { sort: shellOrder });
+            if (shellOrder === 1) outputTraces(inner, { sort: shellOrder, shell: true });
 
-            outputTraces(next.shells, { sort: shellOrder });
+            outputTraces(shells, { sort: shellOrder, shell: true });
 
             // output outer polygons
-            if (shellOrder === -1) outputTraces(inner, { sort: shellOrder });
+            if (shellOrder === -1) outputTraces(inner, { sort: shellOrder, shell: true });
 
             // output thin fill
             print.setType('thin fill');
diff --git a/src/kiri/conf.js b/src/kiri/conf.js
index 76cffb75..f63f51a1 100644
--- a/src/kiri/conf.js
+++ b/src/kiri/conf.js
@@ -364,6 +364,7 @@ const conf = exports({
                 outputPurgeTower: 0,
                 outputBeltFirst: false,
                 outputAvoidGaps: true,
+                outputAlternating: false,
                 outputLayerRetract: false,
                 outputOriginCenter: true,
                 outputLoops: 0,
diff --git a/src/kiri/init.js b/src/kiri/init.js
index f1bfceec..ac2e32ed 100644
--- a/src/kiri/init.js
+++ b/src/kiri/init.js
@@ -1906,7 +1906,7 @@ gapp.register("kiri.init", [], (root, exports) => {
             knifeSep:            uc.newBlank({class:"pop-sep", modes:LASER}),
             knifeOn:             uc.newBoolean(LANG.enable, onBooleanClick, {title:LANG.ou_drkn_l, modes:LASER}),
 
-            output:              uc.newGroup(LANG.ou_menu, null, {modes:GCODE}),
+            output:              uc.newGroup(LANG.ou_menu, null, {class: "fdmout", modes:GCODE}),
             outputLaserPower:    uc.newInput(LANG.ou_powr_s, {title:LANG.ou_powr_l, convert:uc.toInt, bound:uc.bound(1,100), modes:LASER}),
             outputLaserSpeed:    uc.newInput(LANG.ou_sped_s, {title:LANG.ou_sped_l, convert:uc.toInt, modes:LASER}),
             laserSep:            uc.newBlank({class:"pop-sep", modes:LASER}),
@@ -1932,6 +1932,7 @@ gapp.register("kiri.init", [], (root, exports) => {
             fdmSep:              uc.newBlank({class:"pop-sep", modes:FDM}),
             outputLayerRetract:  uc.newBoolean(LANG.ad_lret_s, onBooleanClick, {title:LANG.ad_lret_l, modes:FDM}),
             outputAvoidGaps:     uc.newBoolean(LANG.ad_agap_s, onBooleanClick, {title:LANG.ad_agap_l, modes:FDM}),
+            outputAlternating:   uc.newBoolean(LANG.ad_altr_s, onBooleanClick, {title:LANG.ad_altr_l, modes:FDM}),
             outputBeltFirst:     uc.newBoolean(LANG.ad_lbir_s, onBooleanClick, {title:LANG.ad_lbir_l, show: isBelt, modes:FDM}),
             camConventional:     uc.newBoolean(LANG.ou_conv_s, onBooleanClick, {title:LANG.ou_conv_l, modes:CAM}),
             camEaseDown:         uc.newBoolean(LANG.cr_ease_s, onBooleanClick, {title:LANG.cr_ease_l, modes:CAM}),
diff --git a/src/kiri/print.js b/src/kiri/print.js
index 15e50776..6d4da5e3 100644
--- a/src/kiri/print.js
+++ b/src/kiri/print.js
@@ -67,7 +67,11 @@ class Print {
 
     // fdm & laser
     polyPrintPath(poly, startPoint, output, options = {}) {
-        poly.setClockwise();
+        if (options.ccw) {
+            poly.setCounterClockwise();
+        } else {
+            poly.setClockwise();
+        }
 
         const scope = this;
         const { settings } = scope;
diff --git a/web/kiri/index.css b/web/kiri/index.css
index ed24796a..00dc4d3d 100644
--- a/web/kiri/index.css
+++ b/web/kiri/index.css
@@ -1690,8 +1690,11 @@ th, tr, td, label {
 .set-pop.xdown {
     transform: translateY(-25%) !important;
 }
+.set-pop.fdmout {
+    transform: translateY(-63%) !important;
+}
 .set-pop.fdmadv {
-    transform: translateY(-75%) !important;
+    transform: translateY(-74%) !important;
 }
 .set-pop.rough {
     transform: translateY(-14%) !important;
diff --git a/web/kiri/lang/en.js b/web/kiri/lang/en.js
index ee62476e..9e1321cb 100644
--- a/web/kiri/lang/en.js
+++ b/web/kiri/lang/en.js
@@ -655,6 +655,8 @@ self.kiri.lang['en-us'] = {
     ad_abkl_l:      ["for better flat surface finish","use micro-movements to cancel","backlash in solid layer output","in millimeters","0 to disable","if your firmware has M425","put that in the gcode header","and leave this as 0"],
     ad_lbir_s:      "belt first",
     ad_lbir_l:      ["always print shells touching the","belt before any other shells"],
+    ad_altr_s:      "alternating",
+    ad_altr_l:      ["alternate shell winding order","clockwise / counter-clockwise"],
     ad_lret_s:      "layer retract",
     ad_lret_l:      ["force filament retraction","between layers"],
     ad_agap_s:      "avoid gaps",