diff --git a/main.js b/main.js
index 7a13bd5d..2b4356b6 100644
--- a/main.js
+++ b/main.js
@@ -629,7 +629,7 @@ void (function addDragToUpload() {
 async function generate(options) {
   try {
     const timeStart = performance.now();
-    const {seed: precreatedSeed} = options || {};
+    const {seed: precreatedSeed, graph: precreatedGraph} = options || {};
 
     invokeActiveZooming();
     setSeed(precreatedSeed);
@@ -638,11 +638,9 @@ async function generate(options) {
     applyMapSize();
     randomizeOptions();
 
-    if (shouldRegenerateGrid()) {
-      placePoints();
-      calculateVoronoi(grid, grid.points);
-    }
-    await HeightmapGenerator.generate();
+    if (shouldRegenerateGrid(grid)) grid = precreatedGraph || generateGrid();
+    else delete grid.cells.h;
+    grid.cells.h = await HeightmapGenerator.generate(grid);
 
     markFeatures();
     markupGridOcean();
@@ -654,6 +652,7 @@ async function generate(options) {
     calculateMapCoordinates();
     calculateTemperatures();
     generatePrecipitation();
+
     reGraph();
     drawCoastline();
 
@@ -736,52 +735,13 @@ function setSeed(precreatedSeed) {
   Math.random = aleaPRNG(seed);
 }
 
-// check if new grid graph should be generated or we can use the existing one
-function shouldRegenerateGrid() {
-  if (!grid.spacing) return true;
-  const cellsDesired = +byId("pointsInput").dataset.cells;
-  const newSpacing = rn(Math.sqrt((graphWidth * graphHeight) / cellsDesired), 2);
-  return grid.spacing !== newSpacing;
-}
-
-// Place points to calculate Voronoi diagram
-function placePoints() {
-  TIME && console.time("placePoints");
-  Math.random = aleaPRNG(seed); // reset PRNG
-
-  const cellsDesired = +byId("pointsInput").dataset.cells;
-  const spacing = rn(Math.sqrt((graphWidth * graphHeight) / cellsDesired), 2); // spacing between points before jirrering
-  grid.spacing = spacing;
-  grid.boundary = getBoundaryPoints(graphWidth, graphHeight, spacing);
-  grid.points = getJitteredGrid(graphWidth, graphHeight, spacing); // jittered square grid
-  grid.cellsX = Math.floor((graphWidth + 0.5 * spacing - 1e-10) / spacing);
-  grid.cellsY = Math.floor((graphHeight + 0.5 * spacing - 1e-10) / spacing);
-  TIME && console.timeEnd("placePoints");
-}
-
-// calculate Delaunay and then Voronoi diagram
-function calculateVoronoi(graph, points) {
-  TIME && console.time("calculateDelaunay");
-  const n = points.length;
-  const allPoints = points.concat(grid.boundary);
-  const delaunay = Delaunator.from(allPoints);
-  TIME && console.timeEnd("calculateDelaunay");
-
-  TIME && console.time("calculateVoronoi");
-  const voronoi = new Voronoi(delaunay, allPoints, n);
-  graph.cells = voronoi.cells;
-  graph.cells.i = n < 65535 ? Uint16Array.from(d3.range(n)) : Uint32Array.from(d3.range(n)); // array of indexes
-  graph.vertices = voronoi.vertices;
-  TIME && console.timeEnd("calculateVoronoi");
-}
-
 // Mark features (ocean, lakes, islands) and calculate distance field
 function markFeatures() {
   TIME && console.time("markFeatures");
   Math.random = aleaPRNG(seed); // get the same result on heightmap edit in Erase mode
 
-  const cells = grid.cells,
-    heights = grid.cells.h;
+  const cells = grid.cells;
+  const heights = grid.cells.h;
   cells.f = new Uint16Array(cells.i.length); // cell feature number
   cells.t = new Int8Array(cells.i.length); // cell type: 1 = land coast; -1 = water near coast
   grid.features = [0];
@@ -1201,8 +1161,8 @@ function generatePrecipitation() {
 // recalculate Voronoi Graph to pack cells
 function reGraph() {
   TIME && console.time("reGraph");
-  let {cells, points, features} = grid;
-  const newCells = {p: [], g: [], h: []}; // to store new data
+  const {cells, points, features} = grid;
+  const newCells = {p: [], g: [], h: []}; // store new data
   const spacing2 = grid.spacing ** 2;
 
   for (const i of cells.i) {
@@ -1236,14 +1196,17 @@ function reGraph() {
     newCells.h.push(height);
   }
 
-  calculateVoronoi(pack, newCells.p);
-  cells = pack.cells;
-  cells.p = newCells.p; // points coordinates [x, y]
-  cells.g = grid.cells.i.length < 65535 ? Uint16Array.from(newCells.g) : Uint32Array.from(newCells.g); // reference to initial grid cell
-  cells.q = d3.quadtree(cells.p.map((p, d) => [p[0], p[1], d])); // points quadtree for fast search
-  cells.h = new Uint8Array(newCells.h); // heights
-  cells.area = new Uint16Array(cells.i.length); // cell area
-  cells.i.forEach(i => (cells.area[i] = Math.abs(d3.polygonArea(getPackPolygon(i)))));
+  function getCellArea(i) {
+    const area = Math.abs(d3.polygonArea(getPackPolygon(i)));
+    return Math.min(area, 65535);
+  }
+
+  pack = calculateVoronoi(newCells.p, grid.boundary);
+  pack.cells.p = newCells.p;
+  pack.cells.g = getTypedArray(grid.points.length).from(newCells.g);
+  pack.cells.q = d3.quadtree(newCells.p.map(([x, y], i) => [x, y, i]));
+  pack.cells.h = getTypedArray(100).from(newCells.h);
+  pack.cells.area = getTypedArray(65535).from(pack.cells.i).map(getCellArea);
 
   TIME && console.timeEnd("reGraph");
 }
@@ -1946,7 +1909,11 @@ function showStatistics() {
 
 const regenerateMap = debounce(async function (options) {
   WARN && console.warn("Generate new random map");
-  showLoading();
+
+  const cellsDesired = +byId("pointsInput").dataset.cells;
+  const shouldShowLoading = cellsDesired > 10000;
+
+  shouldShowLoading && showLoading();
   closeDialogs("#worldConfigurator, #options3d");
   customization = 0;
   resetZoom(1000);
@@ -1955,7 +1922,7 @@ const regenerateMap = debounce(async function (options) {
   restoreLayers();
   if (ThreeD.options.isOn) ThreeD.redraw();
   if ($("#worldConfigurator").is(":visible")) editWorld();
-  hideLoading();
+  shouldShowLoading && hideLoading();
 }, 1000);
 
 // clear the map
diff --git a/modules/dynamic/auto-update.js b/modules/dynamic/auto-update.js
index 08b9c056..abeee814 100644
--- a/modules/dynamic/auto-update.js
+++ b/modules/dynamic/auto-update.js
@@ -520,4 +520,9 @@ export function resolveVersionConflicts(version) {
       if (!zone.dataset.type) zone.dataset.type = "Unknown";
     });
   }
+
+  if (version < 1.84) {
+    // v1.84.0 added grid.cellsDesired to stored data
+    if (!grid.cellsDesired) grid.cellsDesired = rn((graphWidth * graphHeight) / grid.spacing ** 2, -3);
+  }
 }
diff --git a/modules/dynamic/heightmap-selection.js b/modules/dynamic/heightmap-selection.js
index 69b89815..90bfdec8 100644
--- a/modules/dynamic/heightmap-selection.js
+++ b/modules/dynamic/heightmap-selection.js
@@ -1,4 +1,6 @@
 const initialSeed = generateSeed();
+let graph = getGraph(grid);
+
 appendStyleSheet();
 insertEditorHtml();
 addListeners();
@@ -8,6 +10,7 @@ export function open() {
 
   const $templateInput = byId("templateInput");
   setSelected($templateInput.value);
+  graph = getGraph(graph);
 
   $("#heightmapSelection").dialog({
     title: "Select Heightmap",
@@ -30,8 +33,7 @@ export function open() {
         lock("template");
 
         const seed = getSeed();
-        Math.random = aleaPRNG(seed);
-        regeneratePrompt({seed});
+        regeneratePrompt({seed, graph});
 
         $(this).dialog("close");
       }
@@ -182,13 +184,14 @@ function insertEditorHtml() {
   </div>`;
 
   byId("dialogs").insertAdjacentHTML("beforeend", heightmapSelectionHtml);
+
   const sections = document.getElementsByClassName("heightmap-selection_container");
 
   sections[0].innerHTML = Object.keys(heightmapTemplates)
     .map(key => {
       const name = heightmapTemplates[key].name;
       Math.random = aleaPRNG(initialSeed);
-      const heights = generateHeightmap(key);
+      const heights = HeightmapGenerator.fromTemplate(graph, key);
       const dataUrl = drawHeights(heights);
 
       return /* html */ `<article data-id="${key}" data-seed="${initialSeed}">
@@ -220,12 +223,8 @@ function addListeners() {
     if (!article) return;
 
     const id = article.dataset.id;
-    if (event.target.matches("span.icon-cw")) {
-      const seed = generateSeed();
-      article.dataset.seed = seed;
-      Math.random = aleaPRNG(seed);
-      drawTemplatePreview(id);
-    } else setSelected(id);
+    if (event.target.matches("span.icon-cw")) regeneratePreview(article, id);
+    setSelected(id);
   });
 
   byId("heightmapSelectionRenderOcean").on("change", redrawAll);
@@ -254,12 +253,18 @@ function getName(id) {
   return isTemplate ? heightmapTemplates[id].name : precreatedHeightmaps[id].name;
 }
 
+function getGraph(currentGraph) {
+  const newGraph = shouldRegenerateGrid(currentGraph) ? generateGrid() : deepCopy(currentGraph);
+  delete newGraph.cells.h;
+  return newGraph;
+}
+
 function drawHeights(heights) {
   const canvas = document.createElement("canvas");
-  canvas.width = grid.cellsX;
-  canvas.height = grid.cellsY;
+  canvas.width = graph.cellsX;
+  canvas.height = graph.cellsY;
   const ctx = canvas.getContext("2d");
-  const imageData = ctx.createImageData(grid.cellsX, grid.cellsY);
+  const imageData = ctx.createImageData(graph.cellsX, graph.cellsY);
 
   const schemeId = byId("heightmapSelectionColorScheme").value;
   const scheme = getColorScheme(schemeId);
@@ -281,32 +286,30 @@ function drawHeights(heights) {
   return canvas.toDataURL("image/png");
 }
 
-function generateHeightmap(id) {
-  const heights = new Uint8Array(grid.points.length);
-  // use cells number of the current graph, no matter what UI input value is
-  const cellsDesired = rn((graphWidth * graphHeight) / grid.spacing ** 2, -3);
-
-  HeightmapGenerator.setHeights(heights, cellsDesired);
-  const newHeights = HeightmapGenerator.fromTemplate(id);
-  HeightmapGenerator.cleanup();
-  return newHeights;
-}
-
 function drawTemplatePreview(id) {
-  const heights = generateHeightmap(id);
+  const heights = HeightmapGenerator.fromTemplate(graph, id);
   const dataUrl = drawHeights(heights);
   const article = byId("heightmapSelection").querySelector(`[data-id="${id}"]`);
   article.querySelector("img").src = dataUrl;
 }
 
 async function drawPrecreatedHeightmap(id) {
-  const heights = await HeightmapGenerator.fromPrecreated(id);
+  const heights = await HeightmapGenerator.fromPrecreated(graph, id);
   const dataUrl = drawHeights(heights);
   const article = byId("heightmapSelection").querySelector(`[data-id="${id}"]`);
   article.querySelector("img").src = dataUrl;
 }
 
+function regeneratePreview(article, id) {
+  graph = getGraph(graph);
+  const seed = generateSeed();
+  article.dataset.seed = seed;
+  Math.random = aleaPRNG(seed);
+  drawTemplatePreview(id);
+}
+
 function redrawAll() {
+  graph = getGraph(graph);
   const articles = byId("heightmapSelection").querySelectorAll(`article`);
   for (const article of articles) {
     const {id, seed} = article.dataset;
diff --git a/modules/heightmap-generator.js b/modules/heightmap-generator.js
index 9fd95cc1..feae9c1e 100644
--- a/modules/heightmap-generator.js
+++ b/modules/heightmap-generator.js
@@ -1,47 +1,48 @@
 "use strict";
 
 window.HeightmapGenerator = (function () {
+  let grid = null;
   let heights = null;
   let blobPower;
   let linePower;
 
-  const setHeights = (savedHeights, cellsNumber) => {
-    heights = savedHeights;
-    blobPower = getBlobPower(cellsNumber);
-    linePower = getLinePower(cellsNumber);
+  const setGraph = graph => {
+    const {cellsDesired, cells, points} = graph;
+    heights = cells.h || createTypedArray({maxValue: 100, length: points.length});
+    blobPower = getBlobPower(cellsDesired);
+    linePower = getLinePower(cellsDesired);
+    grid = graph;
   };
 
-  const resetHeights = () => {
-    heights = new Uint8Array(grid.points.length);
-    const cellsNumber = +byId("pointsInput").dataset.cells;
-    blobPower = getBlobPower(cellsNumber);
-    linePower = getLinePower(cellsNumber);
-  };
   const getHeights = () => heights;
 
-  const cleanup = () => (heights = null);
+  const clearData = () => {
+    heights = null;
+    grid = null;
+  };
 
-  const fromTemplate = template => {
-    const templateString = heightmapTemplates[template]?.template || "";
+  const fromTemplate = (graph, id) => {
+    const templateString = heightmapTemplates[id]?.template || "";
     const steps = templateString.split("\n");
 
-    if (!steps.length) throw new Error(`Heightmap template: no steps. Template: ${template}. Steps: ${steps}`);
+    if (!steps.length) throw new Error(`Heightmap template: no steps. Template: ${id}. Steps: ${steps}`);
+    setGraph(graph);
 
     for (const step of steps) {
       const elements = step.trim().split(" ");
-      if (elements.length < 2) throw new Error(`Heightmap template: steps < 2. Template: ${template}. Step: ${elements}`);
+      if (elements.length < 2) throw new Error(`Heightmap template: steps < 2. Template: ${id}. Step: ${elements}`);
       addStep(...elements);
     }
 
     return heights;
   };
 
-  const fromPrecreated = id => {
+  const fromPrecreated = (graph, id) => {
     return new Promise(resolve => {
       // create canvas where 1px corresponts to a cell
       const canvas = document.createElement("canvas");
       const ctx = canvas.getContext("2d");
-      const {cellsX, cellsY} = grid;
+      const {cellsX, cellsY} = graph;
       canvas.width = cellsX;
       canvas.height = cellsY;
 
@@ -51,7 +52,8 @@ window.HeightmapGenerator = (function () {
       img.onload = () => {
         ctx.drawImage(img, 0, 0, cellsX, cellsY);
         const imageData = ctx.getImageData(0, 0, cellsX, cellsY);
-        const heights = getHeightsFromImageData(imageData.data);
+        setGraph(graph);
+        getHeightsFromImageData(imageData.data);
         canvas.remove();
         img.remove();
         resolve(heights);
@@ -59,18 +61,17 @@ window.HeightmapGenerator = (function () {
     });
   };
 
-  const generate = async function () {
-    Math.random = aleaPRNG(seed);
-
+  const generate = async function (graph) {
     TIME && console.time("defineHeightmap");
     const id = byId("templateInput").value;
-    resetHeights();
 
+    Math.random = aleaPRNG(seed);
     const isTemplate = id in heightmapTemplates;
-    grid.cells.h = isTemplate ? fromTemplate(id) : await fromPrecreated(id);
-
-    cleanup();
+    const heights = isTemplate ? fromTemplate(graph, id) : await fromPrecreated(graph, id);
     TIME && console.timeEnd("defineHeightmap");
+
+    clearData();
+    return heights;
   };
 
   function addStep(tool, a2, a3, a4, a5) {
@@ -141,7 +142,7 @@ window.HeightmapGenerator = (function () {
       do {
         const x = getPointInRange(rangeX, graphWidth);
         const y = getPointInRange(rangeY, graphHeight);
-        start = findGridCell(x, y);
+        start = findGridCell(x, y, grid);
         limit++;
       } while (heights[start] + h > 90 && limit < 50);
 
@@ -177,7 +178,7 @@ window.HeightmapGenerator = (function () {
       do {
         const x = getPointInRange(rangeX, graphWidth);
         const y = getPointInRange(rangeY, graphHeight);
-        start = findGridCell(x, y);
+        start = findGridCell(x, y, grid);
         limit++;
       } while (heights[start] < 20 && limit < 50);
 
@@ -223,7 +224,9 @@ window.HeightmapGenerator = (function () {
         limit++;
       } while ((dist < graphWidth / 8 || dist > graphWidth / 3) && limit < 50);
 
-      let range = getRange(findGridCell(startX, startY), findGridCell(endX, endY));
+      const startCell = findGridCell(startX, startY, grid);
+      const endCell = findGridCell(endX, endY, grid);
+      let range = getRange(startCell, endCell);
 
       // get main ridge
       function getRange(cur, end) {
@@ -305,7 +308,7 @@ window.HeightmapGenerator = (function () {
       do {
         startX = getPointInRange(rangeX, graphWidth);
         startY = getPointInRange(rangeY, graphHeight);
-        start = findGridCell(startX, startY);
+        start = findGridCell(startX, startY, grid);
         limit++;
       } while (heights[start] < 20 && limit < 50);
 
@@ -317,7 +320,7 @@ window.HeightmapGenerator = (function () {
         limit++;
       } while ((dist < graphWidth / 8 || dist > graphWidth / 2) && limit < 50);
 
-      let range = getRange(start, findGridCell(endX, endY));
+      let range = getRange(start, findGridCell(endX, endY, grid));
 
       // get main ridge
       function getRange(cur, end) {
@@ -388,8 +391,8 @@ window.HeightmapGenerator = (function () {
     const endX = vert ? Math.floor(graphWidth - startX - graphWidth * 0.1 + Math.random() * graphWidth * 0.2) : graphWidth - 5;
     const endY = vert ? graphHeight - 5 : Math.floor(graphHeight - startY - graphHeight * 0.1 + Math.random() * graphHeight * 0.2);
 
-    const start = findGridCell(startX, startY);
-    const end = findGridCell(endX, endY);
+    const start = findGridCell(startX, startY, grid);
+    const end = findGridCell(endX, endY, grid);
     let range = getRange(start, end);
     const query = [];
 
@@ -502,20 +505,16 @@ window.HeightmapGenerator = (function () {
   }
 
   function getHeightsFromImageData(imageData) {
-    const heights = new Uint8Array(grid.points.length);
     for (let i = 0; i < heights.length; i++) {
       const lightness = imageData[i * 4] / 255;
       const powered = lightness < 0.2 ? lightness : 0.2 + (lightness - 0.2) ** 0.8;
       heights[i] = minmax(Math.floor(powered * 100), 0, 100);
     }
-    return heights;
   }
 
   return {
-    setHeights,
-    resetHeights,
+    setGraph,
     getHeights,
-    cleanup,
     generate,
     fromTemplate,
     fromPrecreated,
diff --git a/modules/io/load.js b/modules/io/load.js
index 30736043..5bd8c69d 100644
--- a/modules/io/load.js
+++ b/modules/io/load.js
@@ -324,7 +324,11 @@ async function parseLoadedData(data) {
 
     void (function parseGridData() {
       grid = JSON.parse(data[6]);
-      calculateVoronoi(grid, grid.points);
+
+      const {cells, vertices} = calculateVoronoi(grid.points, grid.boundary);
+      grid.cells = cells;
+      grid.vertices = vertices;
+
       grid.cells.h = Uint8Array.from(data[7].split(","));
       grid.cells.prec = Uint8Array.from(data[8].split(","));
       grid.cells.f = Uint16Array.from(data[9].split(","));
@@ -333,7 +337,6 @@ async function parseLoadedData(data) {
     })();
 
     void (function parsePackData() {
-      pack = {};
       reGraph();
       reMarkFeatures();
       pack.features = JSON.parse(data[12]);
diff --git a/modules/io/save.js b/modules/io/save.js
index 8e0a74e8..db303eff 100644
--- a/modules/io/save.js
+++ b/modules/io/save.js
@@ -54,8 +54,8 @@ function getMapData() {
 
   const serializedSVG = new XMLSerializer().serializeToString(cloneEl);
 
-  const {spacing, cellsX, cellsY, boundary, points, features} = grid;
-  const gridGeneral = JSON.stringify({spacing, cellsX, cellsY, boundary, points, features});
+  const {spacing, cellsX, cellsY, boundary, points, features, cellsDesired} = grid;
+  const gridGeneral = JSON.stringify({spacing, cellsX, cellsY, boundary, points, features, cellsDesired});
   const packFeatures = JSON.stringify(pack.features);
   const cultures = JSON.stringify(pack.cultures);
   const states = JSON.stringify(pack.states);
diff --git a/modules/submap.js b/modules/submap.js
index dde13a19..ad35e38b 100644
--- a/modules/submap.js
+++ b/modules/submap.js
@@ -41,8 +41,7 @@ window.Submap = (function () {
 
     // create new grid
     applyMapSize();
-    placePoints();
-    calculateVoronoi(grid, grid.points);
+    grid = generateGrid();
     drawScaleBar(scale);
 
     const resampler = (points, qtree, f) => {
diff --git a/modules/ui/general.js b/modules/ui/general.js
index 7cb0f5c3..533b3f47 100644
--- a/modules/ui/general.js
+++ b/modules/ui/general.js
@@ -81,10 +81,10 @@ function handleMouseMove() {
   if (i === undefined) return;
 
   showNotes(d3.event);
-  const g = findGridCell(point[0], point[1]); // grid cell id
+  const gridCell = findGridCell(point[0], point[1], grid);
   if (tooltip.dataset.main) showMainTip();
-  else showMapTooltip(point, d3.event, i, g);
-  if (cellInfo?.offsetParent) updateCellInfo(point, i, g);
+  else showMapTooltip(point, d3.event, i, gridCell);
+  if (cellInfo?.offsetParent) updateCellInfo(point, i, gridCell);
 }
 
 // show note box on hover (if any)
@@ -244,7 +244,7 @@ function updateCellInfo(point, i, g) {
   infoCell.innerHTML = i;
   infoArea.innerHTML = cells.area[i] ? si(getArea(cells.area[i])) + " " + getAreaUnit() : "n/a";
   infoEvelation.innerHTML = getElevation(pack.features[f], pack.cells.h[i]);
-  infoDepth.innerHTML = getDepth(pack.features[f], pack.cells.h[i], point);
+  infoDepth.innerHTML = getDepth(pack.features[f], point);
   infoTemp.innerHTML = convertTemperature(grid.cells.temp[g]);
   infoPrec.innerHTML = cells.h[i] >= 20 ? getFriendlyPrecipitation(i) : "n/a";
   infoRiver.innerHTML = cells.h[i] >= 20 && cells.r[i] ? getRiverInfo(cells.r[i]) : "no";
@@ -276,11 +276,11 @@ function getElevation(f, h) {
 }
 
 // get water depth
-function getDepth(f, h, p) {
+function getDepth(f, p) {
   if (f.land) return "0 " + heightUnit.value; // land: 0
 
   // lake: difference between surface and bottom
-  const gridH = grid.cells.h[findGridCell(p[0], p[1])];
+  const gridH = grid.cells.h[findGridCell(p[0], p[1], grid)];
   if (f.type === "lake") {
     const depth = gridH === 19 ? f.height / 2 : gridH;
     return getHeight(depth, "abs");
@@ -290,9 +290,9 @@ function getDepth(f, h, p) {
 }
 
 // get user-friendly (real-world) height value from map data
-function getFriendlyHeight(p) {
-  const packH = pack.cells.h[findCell(p[0], p[1])];
-  const gridH = grid.cells.h[findGridCell(p[0], p[1])];
+function getFriendlyHeight([x, y]) {
+  const packH = pack.cells.h[findCell(x, y, grid)];
+  const gridH = grid.cells.h[findGridCell(x, y, grid)];
   const h = packH < 20 ? gridH : packH;
   return getHeight(h);
 }
diff --git a/modules/ui/heightmap-editor.js b/modules/ui/heightmap-editor.js
index 23974ad4..aab80c48 100644
--- a/modules/ui/heightmap-editor.js
+++ b/modules/ui/heightmap-editor.js
@@ -117,7 +117,7 @@ function editHeightmap(options) {
 
   function moveCursor() {
     const [x, y] = d3.mouse(this);
-    const cell = findGridCell(x, y);
+    const cell = findGridCell(x, y, grid);
     heightmapInfoX.innerHTML = rn(x);
     heightmapInfoY.innerHTML = rn(y);
     heightmapInfoCell.innerHTML = cell;
@@ -605,8 +605,8 @@ function editHeightmap(options) {
 
     function dragBrush() {
       const r = brushRadius.valueAsNumber;
-      const point = d3.mouse(this);
-      const start = findGridCell(point[0], point[1]);
+      const [x, y] = d3.mouse(this);
+      const start = findGridCell(x, y, grid);
 
       d3.event.on("drag", () => {
         const p = d3.mouse(this);
@@ -664,7 +664,7 @@ function editHeightmap(options) {
       if (Number.isNaN(operand)) return tip("Operand should be a number", false, "error");
       if ((operator === "add" || operator === "subtract") && !Number.isInteger(operand)) return tip("Operand should be an integer", false, "error");
 
-      HeightmapGenerator.setHeights(grid.cells.h);
+      HeightmapGenerator.setGraph(grid);
 
       if (operator === "multiply") HeightmapGenerator.modify(range, 0, operand, 0);
       else if (operator === "divide") HeightmapGenerator.modify(range, 0, 1 / operand, 0);
@@ -673,15 +673,13 @@ function editHeightmap(options) {
       else if (operator === "exponent") HeightmapGenerator.modify(range, 0, 1, operand);
 
       grid.cells.h = HeightmapGenerator.getHeights();
-      HeightmapGenerator.cleanup();
       updateHeightmap();
     }
 
     function smoothAllHeights() {
-      HeightmapGenerator.setHeights(grid.cells.h);
+      HeightmapGenerator.setGraph(grid);
       HeightmapGenerator.smooth(4, 1.5);
       grid.cells.h = HeightmapGenerator.getHeights();
-      HeightmapGenerator.cleanup();
       updateHeightmap();
     }
 
@@ -940,11 +938,8 @@ function editHeightmap(options) {
       const seed = byId("templateSeed").value;
       if (seed) Math.random = aleaPRNG(seed);
 
-      const heights = new Uint8Array(grid.points.length);
-      // use cells number of the current graph, no matter what UI input value is
-      const cellsDesired = rn((graphWidth * graphHeight) / grid.spacing ** 2, -3);
-      HeightmapGenerator.setHeights(heights, cellsDesired);
-
+      grid.cells.h = createTypedArray({maxValue: 100, length: grid.points.length});
+      HeightmapGenerator.setGraph(grid);
       restartHistory();
 
       for (const step of steps) {
@@ -973,7 +968,6 @@ function editHeightmap(options) {
       }
 
       grid.cells.h = HeightmapGenerator.getHeights();
-      HeightmapGenerator.cleanup();
       updateStatistics();
       mockHeightmap();
       if (byId("preview")) drawHeightmapPreview(); // update heightmap preview if opened
diff --git a/modules/ui/ice-editor.js b/modules/ui/ice-editor.js
index 5951e7aa..f07cb6f9 100644
--- a/modules/ui/ice-editor.js
+++ b/modules/ui/ice-editor.js
@@ -65,8 +65,8 @@ function editIce() {
   }
 
   function addIcebergOnClick() {
-    const point = d3.mouse(this);
-    const i = findGridCell(point[0], point[1]);
+    const [x, y] = d3.mouse(this);
+    const i = findGridCell(x, y, grid);
     const c = grid.points[i];
     const s = +document.getElementById("iceSize").value;
 
diff --git a/utils/arrayUtils.js b/utils/arrayUtils.js
index a7f0c35f..5fa9c81d 100644
--- a/utils/arrayUtils.js
+++ b/utils/arrayUtils.js
@@ -1,7 +1,5 @@
 "use strict";
-// FMG utils related to arrays
 
-// return the last element of array
 function last(array) {
   return array[array.length - 1];
 }
@@ -37,9 +35,24 @@ function deepCopy(obj) {
     [Set, s => [...s.values()].map(dcAny)],
     [Date, d => new Date(d.getTime())],
     [Object, dcObject]
-    // other types will be referenced
     // ... extend here to implement their custom deep copy
   ]);
 
   return dcAny(obj);
 }
+
+function getTypedArray(maxValue) {
+  console.assert(
+    Number.isInteger(maxValue) && maxValue >= 0 && maxValue <= 4294967295,
+    `Array maxValue must be an integer between 0 and 4294967295, got ${maxValue}`
+  );
+
+  if (maxValue <= 255) return Uint8Array;
+  if (maxValue <= 65535) return Uint16Array;
+  if (maxValue <= 4294967295) return Uint32Array;
+  return Uint32Array;
+}
+
+function createTypedArray({maxValue, length}) {
+  return new (getTypedArray(maxValue))(length);
+}
diff --git a/utils/graphUtils.js b/utils/graphUtils.js
index 3755f7c1..b345e286 100644
--- a/utils/graphUtils.js
+++ b/utils/graphUtils.js
@@ -1,7 +1,60 @@
 "use strict";
 // FMG utils related to graph
 
-// add boundary points to pseudo-clip voronoi cells
+// check if new grid graph should be generated or we can use the existing one
+function shouldRegenerateGrid(grid) {
+  const cellsDesired = +byId("pointsInput").dataset.cells;
+  if (cellsDesired !== grid.cellsDesired) return true;
+
+  const newSpacing = rn(Math.sqrt((graphWidth * graphHeight) / cellsDesired), 2);
+  const newCellsX = Math.floor((graphWidth + 0.5 * newSpacing - 1e-10) / newSpacing);
+  const newCellsY = Math.floor((graphHeight + 0.5 * newSpacing - 1e-10) / newSpacing);
+
+  return grid.spacing !== newSpacing || grid.cellsX !== newCellsX || grid.cellsY !== newCellsY;
+}
+
+function generateGrid() {
+  Math.random = aleaPRNG(seed); // reset PRNG
+  const {spacing, cellsDesired, boundary, points, cellsX, cellsY} = placePoints();
+  const {cells, vertices} = calculateVoronoi(points, boundary);
+  return {spacing, cellsDesired, boundary, points, cellsX, cellsY, cells, vertices};
+}
+
+// place random points to calculate Voronoi diagram
+function placePoints() {
+  TIME && console.time("placePoints");
+  const cellsDesired = +byId("pointsInput").dataset.cells;
+  const spacing = rn(Math.sqrt((graphWidth * graphHeight) / cellsDesired), 2); // spacing between points before jirrering
+
+  const boundary = getBoundaryPoints(graphWidth, graphHeight, spacing);
+  const points = getJitteredGrid(graphWidth, graphHeight, spacing); // points of jittered square grid
+  const cellsX = Math.floor((graphWidth + 0.5 * spacing - 1e-10) / spacing);
+  const cellsY = Math.floor((graphHeight + 0.5 * spacing - 1e-10) / spacing);
+  TIME && console.timeEnd("placePoints");
+
+  return {spacing, cellsDesired, boundary, points, cellsX, cellsY};
+}
+
+// calculate Delaunay and then Voronoi diagram
+function calculateVoronoi(points, boundary) {
+  TIME && console.time("calculateDelaunay");
+  const allPoints = points.concat(boundary);
+  const delaunay = Delaunator.from(allPoints);
+  TIME && console.timeEnd("calculateDelaunay");
+
+  TIME && console.time("calculateVoronoi");
+  const n = points.length;
+  const voronoi = new Voronoi(delaunay, allPoints, n);
+
+  const cells = voronoi.cells;
+  cells.i = getTypedArray(n).from(d3.range(n)); // array of indexes
+  const vertices = voronoi.vertices;
+  TIME && console.timeEnd("calculateVoronoi");
+
+  return {cells, vertices};
+}
+
+// add points along map edge to pseudo-clip voronoi cells
 function getBoundaryPoints(width, height, spacing) {
   const offset = rn(-1 * spacing);
   const bSpacing = spacing * 2;
@@ -9,15 +62,18 @@ function getBoundaryPoints(width, height, spacing) {
   const h = height - offset * 2;
   const numberX = Math.ceil(w / bSpacing) - 1;
   const numberY = Math.ceil(h / bSpacing) - 1;
-  let points = [];
+  const points = [];
+
   for (let i = 0.5; i < numberX; i++) {
     let x = Math.ceil((w * i) / numberX + offset);
     points.push([x, offset], [x, h + offset]);
   }
+
   for (let i = 0.5; i < numberY; i++) {
     let y = Math.ceil((h * i) / numberY + offset);
     points.push([offset, y], [w + offset, y]);
   }
+
   return points;
 }
 
@@ -40,7 +96,7 @@ function getJitteredGrid(width, height, spacing) {
 }
 
 // return cell index on a regular square grid
-function findGridCell(x, y) {
+function findGridCell(x, y, grid) {
   return Math.floor(Math.min(y / grid.spacing, grid.cellsY - 1)) * grid.cellsX + Math.floor(Math.min(x / grid.spacing, grid.cellsX - 1));
 }
 
@@ -48,7 +104,7 @@ function findGridCell(x, y) {
 function findGridAll(x, y, radius) {
   const c = grid.cells.c;
   let r = Math.floor(radius / grid.spacing);
-  let found = [findGridCell(x, y)];
+  let found = [findGridCell(x, y, grid)];
   if (!r || radius === 1) return found;
   if (r > 0) found = found.concat(c[found[0]]);
   if (r > 1) {