diff --git a/src/kiri/client.js b/src/kiri/client.js
index 00371f5c..5262f4f2 100644
--- a/src/kiri/client.js
+++ b/src/kiri/client.js
@@ -163,7 +163,7 @@ KIRI.work = {
     prepare : function(settings, update, done) {
         send("prepare", { settings }, function(reply) {
             if (reply.progress) {
-                update(reply.progress, reply.message);
+                update(reply.progress, reply.message, reply.layer);
             }
             if (reply.done) {
                 done(reply.output, reply.maxSpeed);
diff --git a/src/kiri/codec.js b/src/kiri/codec.js
index 774cf53d..08f29afb 100644
--- a/src/kiri/codec.js
+++ b/src/kiri/codec.js
@@ -8,7 +8,7 @@
 
     const BASE = self.base, KIRI = self.kiri, handlers = {};
     const freeMem = true;
-    const zeroOut = false;
+    const zeroOut = true;
 
     const codec = KIRI.codec = {
         encode: encode,
diff --git a/src/kiri/main.js b/src/kiri/main.js
index 1c87052b..638ce614 100644
--- a/src/kiri/main.js
+++ b/src/kiri/main.js
@@ -855,9 +855,13 @@
             segNumber = 0,
             startTime,
             lastMsg,
-            now = Date.now();
+            now = Date.now(),
+            output = [];
 
-        KIRI.client.prepare(settings, function(progress, message) {
+        KIRI.client.prepare(settings, function(progress, message, layer) {
+            if (layer) {
+                output.push(KIRI.codec.decode(layer));
+            }
             if (message !== lastMsg) {
                 let mark = Date.now();
                 if (lastMsg) {
@@ -867,7 +871,7 @@
                 startTime = mark;
             }
             API.show.progress(progress, message);
-        }, function (output, maxSpeed) {
+        }, function (oldout, maxSpeed) {
             if (lastMsg) {
                 segtimes[`${segNumber++}_${lastMsg}`] = Date.now() - startTime;
             }
@@ -875,8 +879,8 @@
             API.show.progress(0);
             if (!isCam) setOpacity(0);
 
-            output = KIRI.codec.decode(output);
-            if (feature.preview && output) {
+            // output = KIRI.codec.decode(output);
+            if (feature.preview && output.length) {
                 startTime = Date.now();
                 STACKS.clear();
                 const stack = STACKS.create('print', SPACE.platform.world)
diff --git a/src/kiri/worker.js b/src/kiri/worker.js
index a509f853..afab532e 100644
--- a/src/kiri/worker.js
+++ b/src/kiri/worker.js
@@ -120,8 +120,13 @@ KIRI.worker = {
             return console.log({invalid_print_driver: mode, driver});
         }
 
-        const layers = driver.prepare(widgets, settings, (progress, message) => {
-            send.data({ progress, message });
+        const layers = driver.prepare(widgets, settings, (progress, message, layer) => {
+            const state = { zeros: [] };
+            const emit = { progress, message };
+            if (layer) {
+                emit.layer = KIRI.codec.encode(layer, state)
+            }
+            send.data(emit);
         });
 
         const print = current.print || {};
@@ -132,7 +137,7 @@ KIRI.worker = {
 
         send.done({
             done: true,
-            output: KIRI.codec.encode(layers, state),
+            // output: KIRI.codec.encode(layers, state),
             maxSpeed
         }, state.zeros);
     },
diff --git a/src/mode/cam/prepare.js b/src/mode/cam/prepare.js
index 9a3decb1..5bebfdce 100644
--- a/src/mode/cam/prepare.js
+++ b/src/mode/cam/prepare.js
@@ -33,8 +33,8 @@
             });
         });
 
-        print.render = KIRI.driver.FDM.prepareRender(print.output, progress => {
-            update(0.5 + progress * 0.5, "render");
+        print.render = KIRI.driver.FDM.prepareRender(print.output, (progress, layer) => {
+            update(0.5 + progress * 0.5, "render", layer);
         }, {
             thin: true,
             print: 0,
diff --git a/src/mode/fdm/prepare.js b/src/mode/fdm/prepare.js
index 1eadde3b..9985449b 100644
--- a/src/mode/fdm/prepare.js
+++ b/src/mode/fdm/prepare.js
@@ -365,23 +365,23 @@
             // if layer produced output, append to output array
             if (layerout.length) output.append(layerout);
 
-            // notify progress
-            layerout.layer = layer++;
-            update((layer / maxLayers) * 0.5, "prepare");
-
             // retract after last layer
             if (layer === maxLayers && layerout.length) {
                 layerout.last().retract = true;
             }
 
+            // notify progress
+            layerout.layer = layer++;
+            update((layer / maxLayers) * 0.5, "prepare");
+
             slices = [];
             layerout = [];
             lastOut = undefined;
         }
 
         print.output = output;
-        print.render = FDM.prepareRender(output, progress => {
-            update(0.5 + progress * 0.5, "render");
+        print.render = FDM.prepareRender(output, (progress, layer) => {
+            update(0.5 + progress * 0.5, "render", layer);
         }, { tools: device.extruders, thin: isThin, flat: isFlat, fdm: true });
         return print.render;
     };
@@ -578,7 +578,7 @@
                 });
             });
 
-            update(index / levels.length);
+            update(index / levels.length, output);
         });
 
         return layers;
diff --git a/src/mode/laser/driver.js b/src/mode/laser/driver.js
index 1a1ac37e..1dbd8fc4 100644
--- a/src/mode/laser/driver.js
+++ b/src/mode/laser/driver.js
@@ -135,7 +135,7 @@
                             merged.push(p);
                         }
                     });
-                    update(slices++ / totalSlices);
+                    update((slices++ / totalSlices) * 0.5, "prepare");
                 });
                 let start = newPoint(0,0,0);
                 let gather = [];
@@ -149,7 +149,7 @@
             } else {
                 widget.slices.forEach(function(slice) {
                     sliceEmitObjects(print, slice, output);
-                    update(slices++ / totalSlices);
+                    update((slices++ / totalSlices) * 0.5, "prepare");
                 });
             }
         });
@@ -209,7 +209,9 @@
         //     console.log({laser_it: output});
         // }
 
-        return print.render = FDM.prepareRender(output, update, { thin: true, z: 0, action: "cut" });
+        return print.render = FDM.prepareRender(output, (progress, layer) => {
+            update(0.5 + progress * 0.5, "render", layer);
+        }, { thin: true, z: 0, action: "cut" });
     };
 
     function exportLaser(print, online, ondone) {