diff --git a/src/geo/base.js b/src/geo/base.js
index 9d80758d..611fe5fb 100644
--- a/src/geo/base.js
+++ b/src/geo/base.js
@@ -436,6 +436,7 @@ function orderClosest(array, fn, from) {
 // wrapper for earcut that handles higher order dimensions and finds the
 // two with the greatest delta to pass to the earcut algorith, then returns
 // an unwrapped array in the original dimensions
+// at present, only used by load.obj.parse()
 function triangulate(array, holes, dims, pos) {
     let narray;
     let info;
diff --git a/src/geo/point.js b/src/geo/point.js
index 273e646b..aee11c4c 100644
--- a/src/geo/point.js
+++ b/src/geo/point.js
@@ -37,6 +37,14 @@ class Point {
         };
     }
 
+    toArray() {
+        return [ this.x, this.y, this.z ];
+    }
+
+    toVector3() {
+        return new THREE.Vector3(this.x, this.y, this.z);
+    }
+
     set(x, y, z) {
         this.x = x;
         this.y = y;
diff --git a/src/geo/polygon.js b/src/geo/polygon.js
index 4f0357a9..73197f9f 100644
--- a/src/geo/polygon.js
+++ b/src/geo/polygon.js
@@ -110,6 +110,10 @@ class Polygon {
         return this;
     }
 
+    fromVectors(array) {
+        return this.addVerts(array.map(v => [ ...v ]).flat());
+    }
+
     toObject() {
         return {
             points: this.toArray(),
diff --git a/src/main/mesh.js b/src/main/mesh.js
index 464f4ab2..2f2b14b8 100644
--- a/src/main/mesh.js
+++ b/src/main/mesh.js
@@ -216,6 +216,18 @@ function space_init(data) {
             }
             let { shiftKey, metaKey, ctrlKey, code } = evt;
             switch (code) {
+                case 'Digit1':
+                    return api.mode.sketch();
+                case 'Digit2':
+                    return api.mode.object();
+                case 'Digit3':
+                    return api.mode.tool();
+                case 'Digit4':
+                    return api.mode.surface();
+                case 'Digit5':
+                    return api.mode.face();
+                case 'Digit6':
+                    return api.mode.edge();
                 case 'KeyQ':
                     return api.settings();
                 case 'KeyI':
@@ -261,7 +273,7 @@ function space_init(data) {
                 case 'KeyH':
                     return shiftKey ? selection.hide() : space.view.home();
                 case 'KeyT':
-                    return space.view.top();
+                    return shiftKey ? api.tool.triangulate() : space.view.top();
                 case 'KeyZ':
                     return space.view.reset();
             }
@@ -300,7 +312,7 @@ function space_init(data) {
                         selection.delete();
                     } else {
                         for (let m of selection.models()) {
-                            m.deleteSelections(mode);
+                            m.deleteSelections();
                             space.refresh()
                         }
                     }
diff --git a/src/mesh/api.js b/src/mesh/api.js
index 28f9c3e8..e9702a6f 100644
--- a/src/mesh/api.js
+++ b/src/mesh/api.js
@@ -1065,6 +1065,12 @@ const tool = {
         }
     },
 
+    triangulate() {
+        for (let m of selection.models()) {
+            m.triangulateSelections();
+        }
+    },
+
     rename(models, type = 'model') {
         models = fallback(models, true);
         let model = models[0];
diff --git a/src/mesh/build.js b/src/mesh/build.js
index 7e8d8a70..9182ca6d 100644
--- a/src/mesh/build.js
+++ b/src/mesh/build.js
@@ -353,14 +353,14 @@ function facon(name, sub) {
     return h.i({ class: [ sub || "fa", name ] });
 }
 
-function menu_item(text, fn, short) {
+function menu_item(text, fn, short, id) {
     if (short) {
         short = Array.isArray(short) ? short : [ short ];
         short = div({ class: "short" }, short.map(s => s.startsWith('bi-') ?
             bicon(s) : div(s)
         ));
     }
-    return div({ onclick: fn }, [
+    return div({ id, onclick: fn }, [
         div({ _: text, class: "grow" }),
         short
     ].filter(o => o));
@@ -432,14 +432,14 @@ function ui_build() {
         div({ class: "menu" }, [
             div('Mode'),
             div({ class: "menu-items" }, [
-                div({ _: 'Sketch', id: "mode-sketch", onclick: mode.sketch }),
+                menu_item('Sketch', mode.sketch, '1', 'mode-sketch'),
                 hr(),
-                div({ _: 'Object', id: "mode-object", onclick: mode.object }),
-                div({ _: 'Tool', id: "mode-tool", onclick: mode.tool }),
+                menu_item('Object', mode.object, '2', 'mode-object'),
+                menu_item('Tool', mode.tool, '3', 'mode-tool'),
                 hr(),
-                div({ _: 'Surface', id: "mode-surface", onclick: mode.surface }),
-                div({ _: 'Face', id: "mode-face", onclick: mode.face }),
-                div({ _: 'Edge', id: "mode-edge", onclick: mode.edge }),
+                menu_item('Surface', mode.surface, '4', 'mode-surface'),
+                menu_item('Face', mode.face, '5', 'mode-face'),
+                menu_item('Edge', mode.edge, '6', 'mode-edge'),
             ])
         ]),
         div({ class: "menu sketch-on" }, [
@@ -484,6 +484,7 @@ function ui_build() {
             div('Faces'),
             div({ class: "menu-items" }, [
                 menu_item('Flip Normals', tool.invert),
+                menu_item('Triangulate', tool.triangulate),
                 menu_item('Analyze', tool.analyze),
                 menu_item('Clean', tool.clean),
             ])
diff --git a/src/mesh/model.js b/src/mesh/model.js
index 4daa06b5..2d422389 100644
--- a/src/mesh/model.js
+++ b/src/mesh/model.js
@@ -4,6 +4,8 @@
 
 // dep: add.array
 // dep: add.three
+// dep: geo.polygon
+// dep: geo.polygons
 // dep: moto.license
 // dep: moto.client
 // dep: mesh.object
@@ -13,10 +15,11 @@
 gapp.register("mesh.model", [], (root, exports) => {
 
 const { MeshPhongMaterial, MeshBasicMaterial, LineBasicMaterial } = THREE;
-const { BufferGeometry, BufferAttribute, DoubleSide, Mesh, Vector3 } = THREE;
-const { mesh, moto } = root;
+const { BufferGeometry, BufferAttribute, DoubleSide, Mesh, Vector3, Triangle } = THREE;
+const { base, mesh, moto } = root;
 const { space } = moto;
 const { api } = mesh;
+const { newPolygon, polygons } = base;
 
 const mapp = mesh;
 const worker = moto.client.fn;
@@ -598,19 +601,13 @@ mesh.model = class MeshModel extends mesh.object {
         }
     }
 
-    clearSelections() {
-        // clear face selections (since they've been deleted);
-        this.sel.faces = [];
-        this.updateSelections();
-    }
-
-    deleteSelections(mode) {
+    collectFacesByMaterialIndex(index) {
         let { geometry } = this.mesh;
         let { groups } = geometry;
         let { array } = geometry.attributes.position;
         let newtot = 0;
         // filter to unselected groups
-        groups = groups.filter(g => g.materialIndex === 0);
+        groups = groups.filter(g => g.materialIndex === index);
         for (let group of groups) {
             let start = group.start * 3;
             let count = group.count * 3;
@@ -631,12 +628,56 @@ mesh.model = class MeshModel extends mesh.object {
             newverts.set(slice, pos);
             pos += count;
         }
-        this.reload(newverts);
+        return newverts;
+    }
+
+    clearSelections() {
         // clear face selections (since they've been deleted);
         this.sel.faces = [];
         this.updateSelections();
     }
 
+    triangulateSelections() {
+        let selverts = this.collectFacesByMaterialIndex(1);
+        if (selverts?.length) {
+            let points = [...selverts].group(3).map(a => new Vector3().fromArray(a));
+            let tris = points.group(3).map(a => new Triangle(...a));
+            let norms = tris.map(t => t.getNormal(new Vector3()));
+            let norm = norms.reduce((a,b) => a.add(b)).normalize();
+            // compute quaternion and rotate triangles to face Z up
+            const targetNorm = new THREE.Vector3(0, 0, 1);
+            const rotato = new THREE.Quaternion().setFromUnitVectors(norm, targetNorm);
+            points.forEach(p => p.applyQuaternion(rotato));
+            // union and earcut the result
+            let polys = tris.map(t => newPolygon().fromVectors([ t.a, t.b, t.c ]));
+            let union = polygons.union(polys,0,true);
+            let ears = union.map(p => p.earcut()).flat();
+            // unrotate using the same quaternion
+            rotato.invert();
+            let nupoints = ears.map(p => p.points).flat().map(p => p.toVector3());
+            nupoints.forEach(p => p.applyQuaternion(rotato));
+            let nuverts = nupoints.map(p => p.toArray()).flat().toFloat32();
+            // remove selection and append nuverts
+            this.deleteSelections(nuverts);
+        }
+    }
+
+    deleteSelections(append) {
+        let newverts = this.collectFacesByMaterialIndex(0);
+        if (newverts) {
+            if (append) {
+                let all = new Float32Array(newverts.length + append.length);
+                all.set(newverts);
+                all.set(append, newverts.length);
+                newverts = all;
+            }
+            this.reload(newverts);
+            // clear face selections (since they've been deleted);
+            this.sel.faces = [];
+            this.updateSelections();
+        }
+    }
+
     updateSelections() {
         let groups = mesh.util.facesToGroups(this.sel.faces);
         let geo = this.mesh.geometry;
diff --git a/src/mesh/work.js b/src/mesh/work.js
index 00c95b20..b5749a15 100644
--- a/src/mesh/work.js
+++ b/src/mesh/work.js
@@ -164,7 +164,7 @@ let model = {
         let { vertices, name, id } = data;
         let geo = new BufferGeometry();
         geo.setAttribute('position', new BufferAttribute(vertices, 3));
-        cacheUpdate(id, { name, geo, mkey: '' });
+        cacheUpdate(id, { name, geo, mkey: undefined, tool: undefined });
     },
 
     // merge several model vertices into a single array