diff --git a/release.md b/release.md
index b8244c3d..ec01a9b3 100644
--- a/release.md
+++ b/release.md
@@ -3,7 +3,7 @@
 Full docs @ https://docs.grid.space/projects/kiri-moto
 
 
-# Release 3.8
+# Release 3.8 (2023-01-21)
 
 * update server-side sample module code
 * various fixes and improvements to CAM indexing
@@ -23,6 +23,7 @@ Full docs @ https://docs.grid.space/projects/kiri-moto
 * CAM fix tracing nested polyline offset ordering
 * CAM refactor of contouring yields 2x - 20x speedup
 * CAM update traces to async slicing, fix use with flip
+* CAM add threading support for all slicing ops
 
 - refactor object/group storage model in Mesh:Tool
 - add omit pocket to rough and outline
@@ -85,6 +86,7 @@ Full docs @ https://docs.grid.space/projects/kiri-moto
 * add CAM Z bottom inversion option to flip operator
 * add CAM custom gcode operator (can be used for pausing, too)
 * add CAM z extend option on registration op independent of "Z Thru" global
+* add CAM pocket surface selection filter by angle
 * add optional CAM operation notes (helps with many similar ops)
 * add option to limit CAM trace ops to Z bottom limit (when in use)
 * extend url loading of workspaces to all formats
diff --git a/src/kiri-mode/cam/client.js b/src/kiri-mode/cam/client.js
index 259d4646..d397fddf 100644
--- a/src/kiri-mode/cam/client.js
+++ b/src/kiri-mode/cam/client.js
@@ -844,6 +844,7 @@ CAM.init = function(kiri, api) {
         func.clearPops();
         alert = api.show.alert("analyzing surfaces...", 1000);
         let surfaces = poppedRec.surfaces;
+        let radians = poppedRec.follow * DEG2RAD;
         CAM.surface_prep(currentIndex * RAD2DEG, () => {
             api.hide.alert(alert);
             alert = api.show.alert("[esc] cancels surface editing");
@@ -851,7 +852,7 @@ CAM.init = function(kiri, api) {
                 let widget = api.widgets.forid(wid);
                 if (widget && arr.length)
                 for (let faceid of arr) {
-                    CAM.surface_toggle(widget, faceid, faceids => {
+                    CAM.surface_toggle(widget, faceid, radians, faceids => {
                         // surfaces[widget.id] = faceids;
                     });
                 }
@@ -864,7 +865,7 @@ CAM.init = function(kiri, api) {
             let min = Math.min(face.a, face.b, face.c);
             let faceid = min / 3;
             let widget = lastWidget = obj.object.widget;
-            CAM.surface_toggle(widget, faceid, faceids => {
+            CAM.surface_toggle(widget, faceid, radians, faceids => {
                 surfaces[widget.id] = faceids;
             });
         };
@@ -1338,10 +1339,11 @@ CAM.init = function(kiri, api) {
         plunge:    'camPocketPlunge',
         expand:    'camPocketExpand',
         smooth:    'camPocketSmooth',
-        refine:    'cmaPocketRefine',
+        refine:    'camPocketRefine',
+        follow:    'camPocketFollow',
         contour:   'camPocketContour',
         engrave:   'camPocketEngrave',
-        outline:   'cmaPocketOutline',
+        outline:   'camPocketOutline',
         tolerance: 'camTolerance',
     }).inputs = {
         tool:      UC.newSelect(LANG.cc_tool, {}, "tools"),
@@ -1354,8 +1356,9 @@ CAM.init = function(kiri, api) {
         sep:       UC.newBlank({class:"pop-sep"}),
         expand:    UC.newInput(LANG.cp_xpnd_s, {title:LANG.cp_xpnd_l, convert:UC.toFloat, units:true, show:() => !poppedRec.contour}),
         refine:    UC.newInput(LANG.cp_refi_s, {title:LANG.cp_refi_l, convert:UC.toInt, show:() => poppedRec.contour}),
-        smooth:    UC.newInput(LANG.cp_smoo_s, {title:LANG.cp_smoo_l, convert:UC.toFloat, units:true}),
+        smooth:    UC.newInput(LANG.cp_smoo_s, {title:LANG.cp_smoo_l, convert:UC.toInt}),
         tolerance: UC.newInput(LANG.ou_toll_s, {title:LANG.ou_toll_l, convert:UC.toFloat, bound:UC.bound(0,10.0), units:true, round:4, show:() => poppedRec.contour}),
+        follow:    UC.newInput(LANG.cp_foll_s, {title:LANG.cp_foll_l, convert:UC.toFloat}),
         sep:       UC.newBlank({class:"pop-sep"}),
         contour:   UC.newBoolean(LANG.cp_cont_s, undefined, {title:LANG.cp_cont_s}),
         outline:   UC.newBoolean(LANG.cp_outl_s, undefined, {title:LANG.cp_outl_l, show:() => !poppedRec.contour}),
diff --git a/src/kiri-mode/cam/driver.js b/src/kiri-mode/cam/driver.js
index e2de2b28..0ffb20d9 100644
--- a/src/kiri-mode/cam/driver.js
+++ b/src/kiri-mode/cam/driver.js
@@ -37,7 +37,7 @@ kiri.load(api => {
             widget.selectFaces(Object.values(widget._surfaces).flat());
         };
 
-        CAM.surface_toggle = function(widget, face, ondone) {
+        CAM.surface_toggle = function(widget, face, radians, ondone) {
             let surfaces = widget._surfaces = widget._surfaces || {};
             for (let [root, faces] of Object.entries(surfaces)) {
                 if (faces.contains(face)) {
@@ -48,7 +48,7 @@ kiri.load(api => {
                     return;
                 }
             }
-            kiri.client.send("cam_surface_find", { id: widget.id, face }, faces => {
+            kiri.client.send("cam_surface_find", { id: widget.id, face, radians }, faces => {
                 if (faces.length) {
                     surfaces[face] = faces;
                     CAM.surface_show(widget);
@@ -92,9 +92,9 @@ kiri.load(api => {
             }
         };
 
-        CAM.surface_find = function(widget, faces) {
+        CAM.surface_find = function(widget, faces, radians) {
             CAM.surface_prep(widget);
-            return widget.tool.findConnectedSurface(faces, 0.1, 0.0);
+            return widget.tool.findConnectedSurface(faces, radians || 0, 0.0);
         };
 
         kiri.worker.cam_surfaces = function(data, send) {
@@ -114,9 +114,9 @@ kiri.load(api => {
         };
 
         kiri.worker.cam_surface_find = function(data, send) {
-            const { id, face } = data;
+            const { id, face, radians } = data;
             const widget = kiri.worker.cache[id];
-            const faces = CAM.surface_find(widget, [face]);
+            const faces = CAM.surface_find(widget, [face], radians);
             send.done(faces);
         }
 
diff --git a/src/kiri-mode/cam/ops.js b/src/kiri-mode/cam/ops.js
index 503c9077..bfae9a34 100644
--- a/src/kiri-mode/cam/ops.js
+++ b/src/kiri-mode/cam/ops.js
@@ -1054,7 +1054,9 @@ class OpPocket extends CamOp {
                 onupdate: (index, total, msg) => {
                     progress((index / total) * 0.9, msg);
                 },
-                ondone: (slices) => { },
+                ondone: (slices) => {
+                    // console.log({ contour: slices });
+                },
                 contour: {
                     tool,
                     tolerance,
diff --git a/src/kiri-mode/cam/slice.js b/src/kiri-mode/cam/slice.js
index 8fddcc70..973364f1 100644
--- a/src/kiri-mode/cam/slice.js
+++ b/src/kiri-mode/cam/slice.js
@@ -333,13 +333,13 @@ CAM.traces = async function(settings, widget, single) {
     let slicer = new kiri.cam_slicer(widget);
     let indices = [...new Set(Object.keys(slicer.zFlat)
         .map(kv => parseFloat(kv).round(5))
-        .appendAll(Object.entries(slicer.zLine).map(ze => {
-            let [ zk, zv ] = ze;
-            return zv > 1 ? parseFloat(zk).round(5) : null;
-        })
-        .filter(v => v !== null)))]
+        // .appendAll(Object.entries(slicer.zLine).map(ze => {
+        //     let [ zk, zv ] = ze;
+        //     return zv > 1 ? parseFloat(zk).round(5) : null;
+        // })
+        // .filter(v => v !== null))
+        )]
         .sort((a,b) => b - a);
-
     let traces = [];
     // find and trim polys (including open) to shadow
     let oneach = data => {
@@ -369,8 +369,9 @@ CAM.traces = async function(settings, widget, single) {
             traces.push(poly);
         });
     };
-    let opts = { each: oneach, over: false, flatoff: 0, edges: true, openok: true };
+    let opts = { each: oneach, over: false, flatoff: 0, edges: true, openok: true, lines: true };
     await slicer.slice(indices, opts);
+    // pick up bottom features
     opts.over = true;
     await slicer.slice(indices, opts);
     widget.traces = traces;
diff --git a/src/kiri-mode/cam/slicer.js b/src/kiri-mode/cam/slicer.js
index 7e5dbd43..fa0eec39 100644
--- a/src/kiri-mode/cam/slicer.js
+++ b/src/kiri-mode/cam/slicer.js
@@ -10,7 +10,7 @@
 gapp.register("kiri-mode.cam.slicer", [], (root, exports) => {
 
 const { base, kiri } = root;
-const { config, util, polygons, newOrderedLine, newPoint } = base;
+const { config, util, polygons, newOrderedLine, newPoint, newLine } = base;
 const { sliceConnect, sliceDedup } = base;
 const { newSlice } = kiri;
 
@@ -237,18 +237,27 @@ class Slicer {
     }
 
     async sliceBucketMinion(bucket, opt, oneach) {
+        const { decode, decodePointArray } = kiri.codec;
         const slices = (await new Promise(resolve => {
             kiri.minions.queue({
                 cmd: "cam_slice",
-                opt: { lines: false },
+                opt: Object.clone(opt),
                 bucket,
             }, resolve);
         })).slices;
         for (let slice of slices) {
+            slice.polys = decode(slice.polys);
+            if (slice.lines) {
+                slice.lines = decodePointArray(slice.lines)
+                    .group(2)
+                    .map(arr => {
+                        return newLine(arr[0], arr[1])
+                    });
+            }
             oneach(slice);
         }
         // console.log(bucket, slices);
-        return kiri.codec.decode(slices);
+        return slices;
     }
 
     async sliceBucket(bucket, opt, oneach) {
@@ -472,10 +481,19 @@ moto.broker.subscribe("minion.started", msg => {
 
     funcs.cam_slice = (data, seq) => {
         const { bucket, opt } = data;
+        const { encode, encodePointArray } = kiri.codec;
+        // log({ slice: bucket, opt });
         cache.slicer.sliceBucket(bucket, opt, slice => {
             // console.log({ slice });
         }).then(data => {
-            reply({ seq, slices: kiri.codec.encode(data) });
+            data.forEach(rec => {
+                rec.polys = encode(rec.polys);
+                if (rec.lines) {
+                    const points = rec.lines.map(l => [l.p1, l.p2]).flat();
+                    rec.lines = encodePointArray(points);
+                }
+            });
+            reply({ seq, slices: data });
         });
     };
 });
diff --git a/src/kiri-mode/cam/topo.js b/src/kiri-mode/cam/topo.js
index afe59da5..41569523 100644
--- a/src/kiri-mode/cam/topo.js
+++ b/src/kiri-mode/cam/topo.js
@@ -119,6 +119,8 @@ class Topo {
             stepsY,
             boundsX,
             boundsY,
+            minX,
+            minY,
             zMin
         });
 
@@ -311,6 +313,10 @@ class Topo {
             stepsTotal += ((maxX - minX + partOff * 2) / toolStep) | 0;
         }
 
+        if (stepsTotal === 0) {
+            return;
+        }
+
         const box = params.box.clone().expandByVector(new THREE.Vector3(
             partOff, partOff, 0
         ));
@@ -411,7 +417,7 @@ class Probe {
     constructor(params) {
 
         const { data, profile } = params;
-        const { stepsX, stepsY, boundsX, boundsY, zMin } = params;
+        const { stepsX, stepsY, boundsX, boundsY, zMin, minX, minY } = params;
 
         this.params = params;
 
diff --git a/src/kiri/conf.js b/src/kiri/conf.js
index be753879..1979990b 100644
--- a/src/kiri/conf.js
+++ b/src/kiri/conf.js
@@ -514,10 +514,11 @@ const conf = exports({
                 camPocketPlunge: 200,
                 camPocketExpand: 0,
                 camPocketSmooth: 0,
-                cmaPocketRefine: 20,
+                camPocketRefine: 20,
+                camPocketFollow: 5,
                 camPocketContour: false,
                 camPocketEngrave: false,
-                cmaPocketOutline: false,
+                camPocketOutline: false,
                 camDrillTool: 1000,
                 camDrillSpindle: 1000,
                 camDrillDownSpeed: 250,
diff --git a/web/kiri/lang/en.js b/web/kiri/lang/en.js
index 7e854563..78c550b9 100644
--- a/web/kiri/lang/en.js
+++ b/web/kiri/lang/en.js
@@ -527,6 +527,8 @@ self.kiri.lang['en-us'] = {
     cp_xpnd_l:      ["grow selected area to","encompass corners"],
     cp_smoo_s:      "smooth",
     cp_smoo_l:      ["clean up jagged edges caused by angled walls. can speedup and improve pocketing for detailed geometries. recommend starting with values around 1 if slicing takes too long or the contours look jagged"],
+    cp_foll_s:      "selection",
+    cp_foll_l:      ["curvature selection limit in degrees. values closer to 0 will restrict selections to flatter surfaces"],
     cp_refi_s:      "refine",
     cp_refi_l:      ["number of refining passes to perform on contoured polylines. meant to address Z delta sawtoothing caused by faced geometries whereas smoothing handles XY. values > 10 work well for gently contoured geometries with significant Z movement."],
     cp_cont_s:      "contour",