diff --git a/src/mesh/api.js b/src/mesh/api.js
index f591436c..bf67a9dc 100644
--- a/src/mesh/api.js
+++ b/src/mesh/api.js
@@ -1235,6 +1235,7 @@ const tool = {
                 id: m.id, opt
             }).then(data => {
                 data?.vertices && m.reload(data.vertices);
+                return data;
             });
             promises.push(p);
         }
@@ -1255,14 +1256,24 @@ const tool = {
     clean(models) {
         models = fallback(models);
         tool.heal(models, {
+            round: 3,
+            precision: 3,
             merge: false,
-            precision: 2,
             dedup: true,
             clean: true
-        }).then(() => {
+        }).then((data) => {
+            for (let od of data) {
+                let { vertices, zlist } = od;
+                console.log({ zlist });
+                log(`${vertices.length/3} vertices, ${zlist.length} unique Z`);
+            }
             log('cleaning complete').unpin();
             util.defer(selection.update);
         });
+    },
+
+    flatten(models) {
+        fallback(models, false).map(model => model.selectionFlatten());
     }
 };
 
diff --git a/src/mesh/build.js b/src/mesh/build.js
index 3b225bcd..7be0ae46 100644
--- a/src/mesh/build.js
+++ b/src/mesh/build.js
@@ -506,6 +506,7 @@ function ui_build() {
                 menu_item('Triangulate', tool.triangulate, ['bi-shift','T']),
                 menu_item('To Sketch', tool.toSketch),
                 menu_item('Analyze', tool.analyze),
+                menu_item('Flatten', tool.flatten),
                 menu_item('Clean', tool.clean),
             ])
         ]),
diff --git a/src/mesh/model.js b/src/mesh/model.js
index 40352e68..536a3253 100644
--- a/src/mesh/model.js
+++ b/src/mesh/model.js
@@ -682,6 +682,19 @@ mesh.model = class MeshModel extends mesh.object {
         }
     }
 
+    selectionFlatten() {
+        let faces = this.sel.faces;
+        if (faces.length) {
+            worker.model_flatten({ id: this.id, faces }).then(data => {
+                if (data.vertices) {
+                    this.reload(data.vertices);
+                    this.sel.faces = [];
+                    this.updateSelections();
+                }
+            });
+        }
+    }
+
     triangulateSelections() {
         let { polys, quaternion } = this.selectionToRotationPolys();
         if (polys) {
diff --git a/src/mesh/tool.js b/src/mesh/tool.js
index d1b45246..851058bd 100644
--- a/src/mesh/tool.js
+++ b/src/mesh/tool.js
@@ -39,6 +39,41 @@ mesh.tool = class MeshTool {
         return this.indexed;
     }
 
+    listZ() {
+        let verts = this.checkVertices(this.uvert).group(3);
+        let zs = new Set();
+        for (let vert of verts) {
+            zs.add(vert[2]);
+        }
+        return Array.from(zs).sort((a,b) => a - b);
+    }
+
+    flattenZ(faceIdxs) {
+        let { uvert, faces } = this;
+        let zsum = 0;
+        let zunq = [];
+        for (let faceIdx of faceIdxs) {
+            let fv1 = faces[faceIdx * 3 + 0];
+            let fv2 = faces[faceIdx * 3 + 1];
+            let fv3 = faces[faceIdx * 3 + 2];
+            let z1 = uvert[fv1 + 2];
+            let z2 = uvert[fv2 + 2];
+            let z3 = uvert[fv3 + 2];
+            zunq.push(z1,z2,z3);
+            zsum = zsum + z1 + z2 + z3;
+        }
+        let zavg = ((( zsum / (faceIdxs.length * 3) ) * 10000 ) | 0) / 10000;
+        for (let faceIdx of faceIdxs) {
+            let fv1 = faces[faceIdx * 3 + 0];
+            let fv2 = faces[faceIdx * 3 + 1];
+            let fv3 = faces[faceIdx * 3 + 2];
+            uvert[fv1 + 2] = zavg;
+            uvert[fv2 + 2] = zavg;
+            uvert[fv3 + 2] = zavg;
+        }
+        return { unique: zunq.sort().uniq(), average: zavg };
+    }
+
     /**
      * @param {number[]} vertices non-indexed
      */
@@ -46,6 +81,7 @@ mesh.tool = class MeshTool {
         this.checkVertices(vertices, 3);
         let doClean = opt.clean !== false;
         let doDedup = opt.dedup !== false;
+        let round = Math.pow(10, opt.round || 0);
         let faces = [];
         let fcac = {}; // seen face hash
         let fnew = []; // accumulate vertex triplets
@@ -54,6 +90,11 @@ mesh.tool = class MeshTool {
         let prec = this.precision;
         let dups = 0;
         let cull = 0;
+        if (round > 1) {
+            for (let i=0, l=vertices.length; i<l; i++) {
+                vertices[i] = ((vertices[i] * round) | 0) / round;
+            }
+        }
         for (let i=0, l=vertices.length; i<l; i += 3) {
             let x = vertices[i];
             let y = vertices[i+1];
diff --git a/src/mesh/work.js b/src/mesh/work.js
index 3551ba3b..ab242d52 100644
--- a/src/mesh/work.js
+++ b/src/mesh/work.js
@@ -367,6 +367,17 @@ let model = {
         let { id, opt } = data;
         let tool = analyze(id, opt);
         log(`${id} | unrolling...`);
+        let zlist = tool.listZ();
+        let unrolled = tool.unrolled();
+        return { vertices: unrolled.toFloat32(), zlist };
+    },
+
+    flatten(data) {
+        let { id, faces } = data;
+        let tool = analyze(id, { });
+        log(`${id} | flatten...`);
+        let { unique, average } = tool.flattenZ(faces);
+        log(`${id} | average=${average.round(3)} uniques=${unique.length}`);
         let unrolled = tool.unrolled();
         return { vertices: unrolled.toFloat32() };
     },