diff --git a/src/sliceActions/createLines.js b/src/sliceActions/createLines.js
index 2147290..f0deb8a 100644
--- a/src/sliceActions/createLines.js
+++ b/src/sliceActions/createLines.js
@@ -1,24 +1,5 @@
-import { normalize } from './helpers/vector2.js';
-
-function addLine(vertices, lineLookup, lines, a, b, faceIndex) {
-  let index;
-  if (typeof lineLookup[`${b}_${a}`] !== 'undefined') {
-    index = lineLookup[`${b}_${a}`];
-  } else {
-    index = lines.length;
-    lineLookup[`${a}_${b}`] = index;
-
-    const start = { x: vertices[a * 3], y: vertices[a * 3 + 1], z: vertices[a * 3 + 2] };
-    const end = { x: vertices[b * 3], y: vertices[b * 3 + 1], z: vertices[b * 3 + 2] };
-
-    const line = { start, end };
-    const faces = [];
-    lines.push({ line, faces });
-  }
-  lines[index].faces.push(faceIndex);
-
-  return index;
-}
+import * as vector2 from './helpers/vector2.js';
+import * as vector3 from './helpers/vector3.js';
 
 export default function createLines(geometry, settings) {
   const faces = [];
@@ -26,16 +7,9 @@ export default function createLines(geometry, settings) {
   const lineLookup = {};
 
   for (let i = 0; i < geometry.objectIndexes.length; i ++) {
-    const i3 = i * 3;
     const objectIndex = geometry.objectIndexes[i];
-    const normal = {
-      x: geometry.faceNormals[i3],
-      y: geometry.faceNormals[i3 + 1],
-      z: geometry.faceNormals[i3 + 2]
-    };
-    const a = geometry.faces[i3];
-    const b = geometry.faces[i3 + 1];
-    const c = geometry.faces[i3 + 2];
+    const { x: a, y: b, z: c } = getVertex(geometry.faces, i);
+    const normal = calculateNormal(geometry.vertices, a, b, c);
 
     // skip faces that point up or down
     if (normal.y > .999 || normal.y < -.999) {
@@ -47,7 +21,7 @@ export default function createLines(geometry, settings) {
     const indexB = addLine(geometry.vertices, lineLookup, lines, b, c, i);
     const indexC = addLine(geometry.vertices, lineLookup, lines, c, a, i);
 
-    const flatNormal = normalize({ x: normal.z, y: normal.x });
+    const flatNormal = vector2.normalize({ x: normal.z, y: normal.x });
     const lineIndexes = [indexA, indexB, indexC];
 
     faces.push({ lineIndexes, flatNormal, objectIndex });
@@ -55,3 +29,44 @@ export default function createLines(geometry, settings) {
 
   return { lines, faces };
 }
+
+function addLine(vertices, lineLookup, lines, a, b, faceIndex) {
+  let index;
+  if (typeof lineLookup[`${b}_${a}`] !== 'undefined') {
+    index = lineLookup[`${b}_${a}`];
+  } else {
+    index = lines.length;
+    lineLookup[`${a}_${b}`] = index;
+
+    const start = getVertex(vertices, a);
+    const end = getVertex(vertices, b);
+
+    const line = { start, end };
+    const faces = [];
+    lines.push({ line, faces });
+  }
+  lines[index].faces.push(faceIndex);
+
+  return index;
+}
+
+function calculateNormal(vertices, a, b, c) {
+  a = getVertex(vertices, a);
+  b = getVertex(vertices, b);
+  c = getVertex(vertices, c);
+
+  const cb = vector3.subtract(c, b);
+  const ab = vector3.subtract(a, b);
+  const normal = vector3.normalize(vector3.cross(cb, ab));
+
+  return normal;
+}
+
+function getVertex(vertices, i) {
+  const i3 = i * 3;
+  return {
+    x: vertices[i3],
+    y: vertices[i3 + 1],
+    z: vertices[i3 + 2]
+  };
+}
diff --git a/src/sliceActions/helpers/vector3.js b/src/sliceActions/helpers/vector3.js
new file mode 100644
index 0000000..7f227de
--- /dev/null
+++ b/src/sliceActions/helpers/vector3.js
@@ -0,0 +1,38 @@
+export const subtract = (a, b) => ({
+  x: a.x - b.x,
+  y: a.y - b.y,
+  z: a.z - b.z
+});
+export const add = (a, b) => ({
+  x: a.x + b.x,
+  y: a.y + b.y,
+  z: a.z + b.z
+});
+export const scale = (v, factor) => ({
+  x: v.x * factor,
+  y: v.y * factor,
+  z: v.z * factor,
+});
+export const divide = (v, factor) => ({
+  x: v.x / factor,
+  y: v.y / factor,
+  z: v.z / factor
+});
+export const cross = (a, b) => ({
+  x: a.y * b.z - a.z * b.y,
+  y: a.z * b.x - a.x * b.z,
+  z: a.x * b.y - a.y * b.x
+});
+export const equals = (a, b) => a.x === b.x && a.y === b.y && a.z === b.z;
+export const almostEquals = (a, b) => Math.abs(a.x - b.x) < 0.001 && Math.abs(a.y - b.y) < 0.001 && Math.abs(a.z - b.z) < 0.001;
+export const length = (v) => Math.sqrt(v.x * v.x + v.y * v.y + v.z * v.z);
+export const distanceTo = (a, b) => length(subtract(a, b));
+export const normalize = (v) => {
+  const l = length(v);
+
+  return {
+    x: v.x / l,
+    y: v.y / l,
+    z: v.z / l
+  };
+};
diff --git a/src/slicer.js b/src/slicer.js
index a44a447..5c28fc8 100644
--- a/src/slicer.js
+++ b/src/slicer.js
@@ -25,7 +25,6 @@ export function sliceGeometry(settings, geometry, materials, matrix, sync = fals
   }
 
   if (matrix && matrix.isMatrix4) geometry.applyMatrix(matrix);
-  geometry.computeFaceNormals();
 
   const vertices = geometry.vertices.reduce((array, { x, y, z }, i) => {
     const i3 = i * 3;
@@ -41,13 +40,6 @@ export function sliceGeometry(settings, geometry, materials, matrix, sync = fals
     array[i3 + 2] = c;
     return array;
   }, new Uint32Array(geometry.faces.length * 3));
-  const faceNormals = geometry.faces.reduce((array, { normal: { x, y, z } }, i) => {
-    const i3 = i * 3;
-    array[i3] = x;
-    array[i3 + 1] = y;
-    array[i3 + 2] = z;
-    return array;
-  }, new Float32Array(geometry.faces.length * 3));
   const objectIndexes = geometry.faces.reduce((array, { materialIndex }, i) => {
     array[i] = materialIndex;
     return array;
@@ -55,7 +47,7 @@ export function sliceGeometry(settings, geometry, materials, matrix, sync = fals
 
   if (faces.length === 0) throw new Error('Geometry does not contain any data');
 
-  geometry = { vertices, faces, objectIndexes, faceNormals };
+  geometry = { vertices, faces, objectIndexes };
 
   const openObjectIndexes = materials instanceof Array ? materials.map(({ side }) => {
     switch (side) {
@@ -114,8 +106,8 @@ function sliceAsync(settings, geometry, openObjectIndexes, constructLinePreview,
       }
     });
 
-    const { vertices, faces, objectIndexes, faceNormals } = geometry;
-    const buffers = [vertices.buffer, faces.buffer, objectIndexes.buffer, faceNormals.buffer];
+    const { vertices, faces, objectIndexes } = geometry;
+    const buffers = [vertices.buffer, faces.buffer, objectIndexes.buffer];
 
     slicerWorker.postMessage({
       message: 'SLICE',