Lower minimum cell size to 4

build.gradle

@@ -8,7 +8,7 @@ plugins {
 }
 
 group = "fr.sukikui.biomemap"
-version = "0.1.4"
+version = "0.1.5"
 
 def minecraftVersion = '26.1.2'
 def paperApiVersion = "${minecraftVersion}.build.65-stable"
@@ -62,15 +62,17 @@ test {
 }
 
 processResources {
+    def resourceProperties = [
+            NAME: rootProject.name,
+            VERSION: project.version.toString(),
+            PACKAGE: rootProject.group.toString(),
+            AUTHOR: "Sukikui",
+            DESCRIPTION: "Lightweight PaperMC plugin exporting dominant biomes from a selected area to JSON",
+            API_VERSION: minecraftVersion
+    ]
+    inputs.properties(resourceProperties)
     filesMatching("**/plugin.yml") {
-        expand(
-                NAME: rootProject.name,
-                VERSION: version,
-                PACKAGE: rootProject.group.toString(),
-                AUTHOR: "Sukikui",
-                DESCRIPTION: "Lightweight PaperMC plugin exporting dominant biomes from a selected area to JSON",
-                API_VERSION: minecraftVersion
-        )
+        expand(resourceProperties)
     }
 }
 

src/main/java/fr/sukikui/biomemap/command/BiomeMapCommand.java

@@ -3,6 +3,7 @@
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import fr.sukikui.biomemap.export.AsyncBiomeExportTask;
 import fr.sukikui.biomemap.export.BiomeExporter;
+import fr.sukikui.biomemap.util.GridMath;
 import fr.sukikui.biomemap.util.ProgressFormatter;
 import java.io.File;
 import java.nio.file.Path;
@@ -31,8 +32,7 @@
 @SuppressFBWarnings("EI_EXPOSE_REP2")
 public final class BiomeMapCommand implements CommandExecutor, TabCompleter {
 
-  private static final int CHUNK_SIZE = 16;
-  private static final int MIN_CELL_SIZE = 8;
+  private static final int MIN_CELL_SIZE = 4;
   private static final String CHAT_PREFIX = "§8[§b§lBiomeMap§8] §r";
   private static final int PLAYER_STATUS_MAP_MAX_WIDTH = 28;
   private static final int PLAYER_STATUS_MAP_MAX_HEIGHT = 10;
@@ -173,14 +173,11 @@ public boolean onCommand(CommandSender sender, Command command, String label, St
 
     long totalCells = (long) width * height;
     long totalChunks;
-    if (cellSize >= CHUNK_SIZE) {
-      int chunksPerCell = Math.max(1, cellSize / CHUNK_SIZE);
-      totalChunks = totalCells * (long) chunksPerCell * chunksPerCell;
-    } else {
-      int cellsPerChunk = CHUNK_SIZE / cellSize;
-      int chunkColumns = Math.max(1, (width + cellsPerChunk - 1) / cellsPerChunk);
-      int chunkRows = Math.max(1, (height + cellsPerChunk - 1) / cellsPerChunk);
-      totalChunks = (long) chunkColumns * chunkRows;
+    try {
+      totalChunks = GridMath.countChunksForGrid(originX, originZ, width, height, cellSize);
+    } catch (IllegalArgumentException ex) {
+      sendError(sender, "Selection is too large to export.");
+      return true;
     }
     notifyInfo(
         sender,
@@ -268,7 +265,7 @@ public List<String> onTabComplete(
       }
       return Collections.emptyList();
     } else if (args.length >= 6) {
-      return List.of("8", "16", "32", "64", "128", "256", "preview");
+      return List.of("4", "8", "16", "32", "64", "128", "256", "preview");
     }
     return Collections.emptyList();
   }
@@ -410,14 +407,18 @@ private int alignCellSize(int requestedSize) {
     if (requestedSize <= MIN_CELL_SIZE) {
       return MIN_CELL_SIZE;
     }
-    if (requestedSize < CHUNK_SIZE) {
-      return CHUNK_SIZE;
+    if (requestedSize < GridMath.CHUNK_SIZE) {
+      int alignedSize = MIN_CELL_SIZE;
+      while (alignedSize < GridMath.CHUNK_SIZE && requestedSize > alignedSize) {
+        alignedSize *= 2;
+      }
+      return alignedSize;
     }
-    int remainder = requestedSize % CHUNK_SIZE;
+    int remainder = requestedSize % GridMath.CHUNK_SIZE;
     if (remainder == 0) {
       return requestedSize;
     }
-    return requestedSize + (CHUNK_SIZE - remainder);
+    return requestedSize + (GridMath.CHUNK_SIZE - remainder);
   }
 
   private void notifyInfo(CommandSender sender, String senderMessage, String logMessage) {

src/main/java/fr/sukikui/biomemap/export/AsyncBiomeExportTask.java

@@ -4,6 +4,7 @@
 import fr.sukikui.biomemap.export.BiomeExporter.BiomeCell;
 import fr.sukikui.biomemap.export.BiomeExporter.BiomeMapExport;
 import fr.sukikui.biomemap.export.BiomeExporter.Point;
+import fr.sukikui.biomemap.util.GridMath;
 import fr.sukikui.biomemap.util.ProgressFormatter;
 import java.io.File;
 import java.io.IOException;
@@ -42,7 +43,7 @@
 @SuppressFBWarnings("EI_EXPOSE_REP2")
 public final class AsyncBiomeExportTask extends BukkitRunnable {
 
-  private static final int CHUNK_SIZE = 16;
+  private static final int CHUNK_SIZE = GridMath.CHUNK_SIZE;
   private static final String CHAT_PREFIX = "§8[§b§lBiomeMap§8] §r";
   private static final long FIRST_PROGRESS_HEARTBEAT_MS = TimeUnit.SECONDS.toMillis(10);
   private static final long PROGRESS_HEARTBEAT_MS = TimeUnit.MINUTES.toMillis(5);
@@ -149,15 +150,10 @@ public AsyncBiomeExportTask(
     this.subChunkSampling = cellSize < CHUNK_SIZE;
     this.chunksPerCell = subChunkSampling ? 1 : Math.max(1, cellSize / CHUNK_SIZE);
     this.cellsPerChunk = subChunkSampling ? Math.max(1, CHUNK_SIZE / cellSize) : 1;
-    if (subChunkSampling) {
-      this.chunkColumns = Math.max(1, (width + cellsPerChunk - 1) / cellsPerChunk);
-      this.chunkRows = Math.max(1, (height + cellsPerChunk - 1) / cellsPerChunk);
-    } else {
-      this.chunkColumns = width * chunksPerCell;
-      this.chunkRows = height * chunksPerCell;
-    }
-    this.chunkStartX = Math.floorDiv(originX, CHUNK_SIZE);
-    this.chunkStartZ = Math.floorDiv(originZ, CHUNK_SIZE);
+    this.chunkColumns = GridMath.countChunksForCells(originX, width, cellSize);
+    this.chunkRows = GridMath.countChunksForCells(originZ, height, cellSize);
+    this.chunkStartX = GridMath.chunkStart(originX);
+    this.chunkStartZ = GridMath.chunkStart(originZ);
     this.chunkBiomes = new String[chunkColumns * chunkRows];
     this.totalChunks = chunkBiomes.length;
     this.chunkCompletedMap = new boolean[chunkBiomes.length];

src/main/java/fr/sukikui/biomemap/util/GridMath.java

@@ -0,0 +1,47 @@
+package fr.sukikui.biomemap.util;
+
+/**
+ * Shared grid/chunk calculations for biome exports.
+ */
+public final class GridMath {
+
+  public static final int CHUNK_SIZE = 16;
+
+  private GridMath() {
+  }
+
+  /**
+   * Counts how many chunks are touched by a cell axis.
+   */
+  public static int countChunksForCells(int origin, int cellCount, int cellSize) {
+    if (cellCount <= 0 || cellSize <= 0) {
+      throw new IllegalArgumentException("Cell count and size must be positive");
+    }
+
+    long minChunk = Math.floorDiv((long) origin, CHUNK_SIZE);
+    long maxBlock = (long) origin + ((long) cellCount * cellSize) - 1L;
+    long maxChunk = Math.floorDiv(maxBlock, CHUNK_SIZE);
+    long span = maxChunk - minChunk + 1L;
+    if (span > Integer.MAX_VALUE) {
+      throw new IllegalArgumentException("Selection spans too many chunks");
+    }
+    return Math.max(1, (int) span);
+  }
+
+  /**
+   * Counts how many chunks are touched by a cell grid.
+   */
+  public static long countChunksForGrid(
+      int originX, int originZ, int width, int height, int cellSize) {
+    long columns = countChunksForCells(originX, width, cellSize);
+    long rows = countChunksForCells(originZ, height, cellSize);
+    return columns * rows;
+  }
+
+  /**
+   * Returns the chunk coordinate containing the provided block coordinate.
+   */
+  public static int chunkStart(int origin) {
+    return Math.floorDiv(origin, CHUNK_SIZE);
+  }
+}

src/test/java/fr/sukikui/biomemap/util/GridMathTest.java

@@ -0,0 +1,33 @@
+package fr.sukikui.biomemap.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class GridMathTest {
+
+  @Test
+  void countsAlignedSubChunkCellsInsideOneChunk() {
+    assertEquals(1, GridMath.countChunksForCells(0, 4, 4));
+    assertEquals(1, GridMath.countChunksForCells(0, 2, 8));
+  }
+
+  @Test
+  void countsOffsetSubChunkCellsCrossingChunkBoundary() {
+    assertEquals(2, GridMath.countChunksForCells(8, 2, 8));
+    assertEquals(2, GridMath.countChunksForCells(12, 3, 4));
+  }
+
+  @Test
+  void countsLargeCellsAcrossMultipleChunks() {
+    assertEquals(4, GridMath.countChunksForCells(0, 2, 32));
+    assertEquals(6, GridMath.countChunksForCells(-32, 3, 32));
+  }
+
+  @Test
+  void rejectsInvalidCellGrid() {
+    assertThrows(IllegalArgumentException.class, () -> GridMath.countChunksForCells(0, 0, 4));
+    assertThrows(IllegalArgumentException.class, () -> GridMath.countChunksForCells(0, 1, 0));
+  }
+}