Improve //hollow command

- Add -p flag to iterate from placement position instead of the
  selection boundaries
- Add -g flag to consider geometry in visibility calculations
- By default, //hollow will no longer open up faces that are touching
  the selection bounding box. The old behaviour can be access with the
  -o flag.

Author: TomyLobo

verification/src/changes/accepted-core-public-api-changes.json

@@ -22,6 +22,13 @@
             "changes": [
                 "METHOD_REMOVED"
             ]
+        },
+        {
+            "type": "com.sk89q.worldedit.EditSession",
+            "member": "Method com.sk89q.worldedit.EditSession.makeCuboidFaces(com.sk89q.worldedit.regions.Region,int,com.sk89q.worldedit.function.pattern.Pattern)",
+            "changes": [
+                "METHOD_NOW_FINAL"
+            ]
         }
     ]
 }

worldedit-core/src/main/java/com/sk89q/worldedit/EditSession.java

@@ -124,17 +124,20 @@
 import com.sk89q.worldedit.world.World;
 import com.sk89q.worldedit.world.biome.BiomeType;
 import com.sk89q.worldedit.world.block.BaseBlock;
+import com.sk89q.worldedit.world.block.BlockCategory;
 import com.sk89q.worldedit.world.block.BlockState;
 import com.sk89q.worldedit.world.block.BlockStateHolder;
 import com.sk89q.worldedit.world.block.BlockType;
 import com.sk89q.worldedit.world.block.BlockTypes;
 import com.sk89q.worldedit.world.generation.TreeType;
+import com.sk89q.worldedit.world.registry.BlockMaterial;
 import com.sk89q.worldedit.world.registry.LegacyMapper;
 import org.apache.logging.log4j.Logger;
 
 import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -2657,6 +2660,43 @@ public int deformRegion(final Region region, final Transform targetTransform, fi
         return affected;
     }
 
+    private static Direction[] getBlockedDirections(Extent extent, BlockVector3 position) {
+        BlockState blockState = extent.getBlock(position);
+        BlockType blockType = blockState.getBlockType();
+        BlockMaterial material = blockState.getMaterial();
+
+        if (material.isAir()) {
+            return NO_DIRECTIONS;
+        }
+        if (material.isLiquid()) {
+            return NO_DIRECTIONS;
+        }
+        Direction[] blockedDirections = BLOCKED_DIRECTIONS_OVERRIDE.get(blockType);
+        if (blockedDirections != null) {
+            return blockedDirections;
+        }
+        if (material.isFullCube()) {
+            return CARDINAL_UPRIGHT_DIRECTIONS;
+        }
+
+        Direction[] result = new Direction[CARDINAL_UPRIGHT_DIRECTIONS.length];
+        int count = 0;
+
+        for (Direction direction : CARDINAL_UPRIGHT_DIRECTIONS) {
+            if (material.isFullFace(direction)) {
+                result[count++] = direction;
+            }
+        }
+
+        // Short-cut for blocks that are blocked in all directions but for some reason not isFullCube
+        // This enables == comparison later
+        if (count == 6) {
+            return CARDINAL_UPRIGHT_DIRECTIONS;
+        }
+
+        return Arrays.copyOf(result, count);
+    }
+
     /**
      * Hollows out the region (Semi-well-defined for non-cuboid selections).
      *
@@ -2666,59 +2706,107 @@ public int deformRegion(final Region region, final Transform targetTransform, fi
      *
      * @return number of blocks affected
      * @throws MaxChangedBlocksException thrown if too many blocks are changed
+     * @deprecated Use {@link EditSession#hollowOutRegion(Region, int, Pattern, boolean, Collection, boolean)} instead.
      */
-    public int hollowOutRegion(Region region, int thickness, Pattern pattern) throws MaxChangedBlocksException {
+    @InlineMe(replacement = "this.hollowOutRegion(region, thickness, pattern, true, null, false)")
+    @Deprecated
+    public final int hollowOutRegion(Region region, int thickness, Pattern pattern) throws MaxChangedBlocksException {
+        return hollowOutRegion(region, thickness, pattern, true, null, false);
+    }
+
+    /**
+     * Hollows out the region (bounding-box mode is semi-well-defined for non-cuboid selections).
+     * The startingPositions parameter takes precedence over usePlacementPosition.
+     *
+     * @param region            the region to hollow out.
+     * @param thickness         the thickness of the shell to leave (manhattan distance)
+     * @param pattern           The block pattern to use
+     * @param openSides         Open up faces touching the bounding box. This matches the legacy behaviour.
+     * @param startingPositions Positions to consider as 'outside'. If null, use the selection bounding box
+     * @param useBlockGeometry  Consider block geometry for visibility calculation
+     * @return number of blocks affected
+     * @throws MaxChangedBlocksException thrown if too many blocks are changed
+     */
+    public int hollowOutRegion(Region region, int thickness, Pattern pattern, boolean openSides, Collection<BlockVector3> startingPositions, boolean useBlockGeometry) throws MaxChangedBlocksException {
         int affected = 0;
 
         final Set<BlockVector3> visible = new HashSet<>();
+        if (startingPositions == null) {
+            // Initialize BFS with selection bounding box
+            final BlockVector3 min = region.getMinimumPoint();
+            final BlockVector3 max = region.getMaximumPoint();
+
+            final int minX = min.x();
+            final int minY = min.y();
+            final int minZ = min.z();
+            final int maxX = max.x();
+            final int maxY = max.y();
+            final int maxZ = max.z();
 
-        // Initialize BFS with selection bounding box
-        final BlockVector3 min = region.getMinimumPoint();
-        final BlockVector3 max = region.getMaximumPoint();
-
-        final int minX = min.x();
-        final int minY = min.y();
-        final int minZ = min.z();
-        final int maxX = max.x();
-        final int maxY = max.y();
-        final int maxZ = max.z();
+            for (int x = minX; x <= maxX; ++x) {
+                for (int y = minY; y <= maxY; ++y) {
+                    visible.add(BlockVector3.at(x, y, minZ));
+                    visible.add(BlockVector3.at(x, y, maxZ));
+                }
+            }
 
-        for (int x = minX; x <= maxX; ++x) {
             for (int y = minY; y <= maxY; ++y) {
-                visible.add(BlockVector3.at(x, y, minZ));
-                visible.add(BlockVector3.at(x, y, maxZ));
+                for (int z = minZ; z <= maxZ; ++z) {
+                    visible.add(BlockVector3.at(minX, y, z));
+                    visible.add(BlockVector3.at(maxX, y, z));
+                }
             }
-        }
 
-        for (int y = minY; y <= maxY; ++y) {
             for (int z = minZ; z <= maxZ; ++z) {
-                visible.add(BlockVector3.at(minX, y, z));
-                visible.add(BlockVector3.at(maxX, y, z));
+                for (int x = minX; x <= maxX; ++x) {
+                    visible.add(BlockVector3.at(x, minY, z));
+                    visible.add(BlockVector3.at(x, maxY, z));
+                }
             }
-        }
 
-        for (int z = minZ; z <= maxZ; ++z) {
-            for (int x = minX; x <= maxX; ++x) {
-                visible.add(BlockVector3.at(x, minY, z));
-                visible.add(BlockVector3.at(x, maxY, z));
+            if (openSides) {
+                // Remove movement blockers from visible list
+                visible.removeIf(blockVector3 -> getBlock(blockVector3).getBlockType().getMaterial().isMovementBlocker());
             }
+        } else {
+            visible.addAll(startingPositions);
         }
 
-        // Remove movement blockers from visible list
-        visible.removeIf(blockVector3 -> getBlock(blockVector3).getBlockType().getMaterial().isMovementBlocker());
-
         // Do BFS to find more visible blocks
         final Queue<BlockVector3> queue = new ArrayDeque<>(visible);
         while (!queue.isEmpty()) {
             final BlockVector3 current = queue.poll();
 
-            final BlockState block = getBlock(current);
-            if (block.getBlockType().getMaterial().isMovementBlocker()) {
-                continue;
+            Direction[] blockedDirections;
+            if (useBlockGeometry) {
+                // Get blocked directions for this block
+                blockedDirections = getBlockedDirections(this, current);
+
+                // Short-cut if blocked in all directions
+                if (blockedDirections == CARDINAL_UPRIGHT_DIRECTIONS) {
+                    continue;
+                }
+            } else {
+                final BlockState block = getBlock(current);
+                if (block.getBlockType().getMaterial().isMovementBlocker()) {
+                    // In non-geometry mode, all movement blockers are assumed to be blocked in all directions, so short-cut here
+                    continue;
+                }
+
+                // All other blocks are assumed to have no blocked directions
+                blockedDirections = NO_DIRECTIONS;
             }
 
-            for (BlockVector3 recurseDirection : CARDINAL_UPRIGHT_OFFSETS) {
-                final BlockVector3 neighbor = current.add(recurseDirection);
+            outer:
+            for (Direction direction : CARDINAL_UPRIGHT_DIRECTIONS) {
+                // Check if this direction is blocked
+                for (Direction blockedDirection : blockedDirections) {
+                    if (blockedDirection == direction) {
+                        continue outer; // skip this direction
+                    }
+                }
+
+                final BlockVector3 neighbor = current.add(direction.toBlockVector());
 
                 if (!region.contains(neighbor)) {
                     continue;
@@ -3171,6 +3259,10 @@ public int morph(BlockVector3 position, double brushSize, int minErodeFaces, int
         return changed;
     }
 
+    /**
+     * Contains no directions.
+     */
+    private static final Direction[] NO_DIRECTIONS = {};
     /**
      * Contains all cardinal and upright directions.
      */
@@ -3184,6 +3276,77 @@ public int morph(BlockVector3 position, double brushSize, int minErodeFaces, int
         .map(Direction::toBlockVector)
         .toArray(BlockVector3[]::new);
 
+    /**
+     * Some blocks need a special case for one reason or another.
+     */
+    private static final Map<BlockType, Direction[]> BLOCKED_DIRECTIONS_OVERRIDE = new HashMap<>();
+
+    static {
+        Arrays.asList(
+            // fullcubes that you can see through on all 6 sides
+            BlockTypes.SPAWNER,
+            BlockTypes.CHEST,
+            BlockTypes.BEACON,
+            BlockTypes.KELP,
+            BlockTypes.KELP_PLANT,
+            BlockTypes.MANGROVE_ROOTS,
+            BlockTypes.ICE,
+
+            BlockTypes.OAK_DOOR,
+            BlockTypes.OAK_TRAPDOOR,
+            // BlockTypes.SPRUCE_DOOR,
+            // BlockTypes.SPRUCE_TRAPDOOR,
+            // BlockTypes.BIRCH_DOOR,
+            // BlockTypes.BIRCH_TRAPDOOR,
+            BlockTypes.JUNGLE_DOOR,
+            BlockTypes.JUNGLE_TRAPDOOR,
+            BlockTypes.ACACIA_DOOR,
+            BlockTypes.ACACIA_TRAPDOOR,
+            // BlockTypes.DARK_OAK_DOOR,
+            // BlockTypes.DARK_OAK_TRAPDOOR,
+            // BlockTypes.MANGROVE_DOOR,
+            BlockTypes.MANGROVE_TRAPDOOR,
+            BlockTypes.CHERRY_DOOR,
+            BlockTypes.CHERRY_TRAPDOOR,
+            // BlockTypes.PALE_OAK_DOOR,
+            // BlockTypes.PALE_OAK_TRAPDOOR,
+            BlockTypes.BAMBOO_DOOR,
+            BlockTypes.BAMBOO_TRAPDOOR,
+            BlockTypes.CRIMSON_DOOR,
+            BlockTypes.CRIMSON_TRAPDOOR,
+            BlockTypes.WARPED_DOOR,
+            BlockTypes.WARPED_TRAPDOOR,
+            BlockTypes.IRON_DOOR,
+            BlockTypes.IRON_TRAPDOOR
+        ).forEach(blockType -> {
+            BLOCKED_DIRECTIONS_OVERRIDE.put(blockType, NO_DIRECTIONS);
+        });
+        BLOCKED_DIRECTIONS_OVERRIDE.put(BlockTypes.TRIAL_SPAWNER, new Direction[] { Direction.UP });
+        BLOCKED_DIRECTIONS_OVERRIDE.put(BlockTypes.VAULT, new Direction[] { Direction.UP, Direction.DOWN });
+        addSeeThroughBlockCategory("minecraft:fall_damage_resetting");
+        addSeeThroughBlockCategory("minecraft:replaceable_by_trees");
+
+        java.util.regex.Pattern pattern = java.util.regex.Pattern.compile("^.*:(?:.*_)?(?:glass|grate|copper_door|copper_trapdoor)(?:_.*)?$");
+        for (BlockType blockType : BlockType.REGISTRY) {
+            if (pattern.matcher(blockType.id()).matches()) {
+                BLOCKED_DIRECTIONS_OVERRIDE.put(blockType, NO_DIRECTIONS);
+            }
+        }
+    }
+
+    private static void addSeeThroughBlockCategory(String blockCategoryKey) {
+        BlockCategory blockCategory = BlockCategory.REGISTRY.get(blockCategoryKey);
+        if (blockCategory == null) {
+            WorldEdit.logger.warn("BlockCategory {} not found during initialization", blockCategoryKey);
+            return;
+        }
+
+        for (BlockType blockType : blockCategory.getAll()) {
+            BLOCKED_DIRECTIONS_OVERRIDE.put(blockType, NO_DIRECTIONS);
+        }
+
+    }
+
     private static double lengthSq(double x, double y, double z) {
         return (x * x) + (y * y) + (z * z);
     }

worldedit-core/src/main/java/com/sk89q/worldedit/command/RegionCommands.java

@@ -79,8 +79,11 @@
 import org.enginehub.piston.annotation.param.Arg;
 import org.enginehub.piston.annotation.param.ArgFlag;
 import org.enginehub.piston.annotation.param.Switch;
+import org.enginehub.piston.exception.CommandException;
 
 import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
 import static com.sk89q.worldedit.command.util.Logging.LogMode.ALL;
@@ -548,15 +551,36 @@ public int deform(Actor actor, LocalSession session, EditSession editSession,
     )
     @CommandPermissions("worldedit.region.hollow")
     @Logging(REGION)
-    public int hollow(Actor actor, EditSession editSession,
+    public int hollow(Actor actor, EditSession editSession, LocalSession session,
                       @Selection Region region,
                       @Arg(desc = "Thickness of the shell to leave", def = "1")
                           int thickness,
                       @Arg(desc = "The pattern of blocks to replace the hollowed area with", def = "air")
-                          Pattern pattern) throws WorldEditException {
+                          Pattern pattern,
+                      @Switch(name = 'o', desc = "Open up faces touching the bounding box. This matches the legacy behaviour.")
+                          boolean openSides,
+                      @Switch(name = 'p', desc = "Consider placement position as 'outside' instead of the selection bounding box. Overrides -o.")
+                          boolean usePlacementPosition,
+                      @Switch(name = 'g', desc = "Consider block geometry for visibility calculation")
+                          boolean useBlockGeometry) throws WorldEditException {
         checkCommandArgument(thickness >= 1, "Thickness must be >= 1");
 
-        int affected = editSession.hollowOutRegion(region, thickness, pattern);
+        final Collection<BlockVector3> startingPositions;
+        if (usePlacementPosition) {
+            BlockVector3 placementPosition = session.getPlacementPosition(actor);
+            if (!region.contains(placementPosition)) {
+                throw new CommandException(
+                    TextComponent.of("Placement position must be inside selection (")
+                        .append(session.getPlacement().getInfo())
+                        .append(TextComponent.of(")")),
+                    ImmutableList.of()
+                );
+            }
+            startingPositions = Collections.singletonList(placementPosition);
+        } else {
+            startingPositions = null;
+        }
+        int affected = editSession.hollowOutRegion(region, thickness, pattern, openSides, startingPositions, useBlockGeometry);
         actor.printInfo(TranslatableComponent.of("worldedit.hollow.changed", TextComponent.of(affected)));
         return affected;
     }