diff --git a/src/kiri-mode/cam/ops.js b/src/kiri-mode/cam/ops.js
index 59648bb9..73a6fcf5 100644
--- a/src/kiri-mode/cam/ops.js
+++ b/src/kiri-mode/cam/ops.js
@@ -227,7 +227,7 @@ class OpRough extends CamOp {
         let shadow = [];
         let slices = [];
         let indices = slicer.interval(roughDown, {
-            down: true, min: zBottom, fit: true, off: 0.01
+            down: true, min: 0, fit: true, off: 0.01
         });
         // shift out first (top-most) slice
         indices.shift();
@@ -510,7 +510,7 @@ class OpOutline extends CamOp {
         let shadow = [];
         let slices = [];
         let intopt = {
-            down: true, min: zBottom, fit: true, off: 0.01,
+            down: true, min: 0, fit: true, off: 0.01,
             max: op.top ? zMax + ztOff : undefined
         };
         let indices = slicer.interval(op.down, intopt);
diff --git a/src/kiri-mode/cam/slicer.js b/src/kiri-mode/cam/slicer.js
index e64cc98f..5bc28ade 100644
--- a/src/kiri-mode/cam/slicer.js
+++ b/src/kiri-mode/cam/slicer.js
@@ -216,7 +216,7 @@ class Slicer {
 
         const promises = []
         for (let bucket of buckets) {
-            promises.push(sliceFn(bucket, opt, slice => {
+            promises.push(sliceFn(bucket, { ...opt, minZ: this.bounds.min.z }, slice => {
                 track.count++;
                 if (opt.progress) {
                     opt.progress(track.count, track.total);
@@ -281,7 +281,7 @@ class Slicer {
         let links = opt.links !== false,
             dedup = opt.dedup !== false,
             edges = opt.edges || false,
-            over = opt.over || false,
+            over = opt.over || z <= opt.minZ,
             debug = opt.debug,
             phash = {},
             lines = [];