Keep huge procedural trees from stalling

Faster leaf support; height capped at 128.

core/src/main/java/com/volmit/iris/engine/object/procedural/tree/ResolvedTree.java

@@ -33,6 +33,8 @@ public final class ResolvedTree extends ResolvedProceduralPlacement {
     private static final long VARIANT_SEED_STRIDE = 7919L;
     private static final double HEIGHT_JITTER_FRACTION = 0.3;
     private static final int MINIMUM_HEIGHT = 2;
+    /** Nearly three times the tallest tree in the packs. Taller settings are clamped so a typo bakes in seconds, not hours. */
+    static final int TALLEST_TREE_BLOCKS = 128;
 
     private final Tree settings;
 
@@ -55,8 +57,8 @@ public final class ResolvedTree extends ResolvedProceduralPlacement {
     protected List<IrisObject> bake(ObjectBuilder blocks) {
         List<IrisObject> baked = new ArrayList<>();
         int count = Math.max(1, settings.variants());
-        int lo = Math.min(settings.heightMin(), settings.heightMax());
-        int hi = Math.max(settings.heightMin(), settings.heightMax());
+        int lo = Math.min(Math.min(settings.heightMin(), settings.heightMax()), TALLEST_TREE_BLOCKS);
+        int hi = Math.min(Math.max(settings.heightMin(), settings.heightMax()), TALLEST_TREE_BLOCKS);
         RNG heightRng = new RNG(settings.seed());
 
         for (int i = 0; i < count; i++) {

core/src/main/java/com/volmit/iris/engine/object/procedural/tree/Tree.java

@@ -104,10 +104,12 @@ public final class Tree {
     private TreeProfile profile = TreeProfile.OAK;
 
     @MinNumber(1)
+    @MaxNumber(ResolvedTree.TALLEST_TREE_BLOCKS)
     @Desc("Minimum trunk height in blocks.")
     private int heightMin = 8;
 
     @MinNumber(1)
+    @MaxNumber(ResolvedTree.TALLEST_TREE_BLOCKS)
     @Desc("Maximum trunk height in blocks.")
     private int heightMax = 12;
 

core/src/main/java/com/volmit/iris/engine/object/procedural/tree/TreeSupport.java

@@ -19,7 +19,10 @@
 package com.volmit.iris.engine.object.procedural.tree;
 
 import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 public final class TreeSupport {
     private static final int LEGAL_DISTANCE = 6;
@@ -28,46 +31,65 @@ public final class TreeSupport {
     private TreeSupport() {
     }
 
+    /**
+     * Grows wood toward the leaves farthest from any, one tendril at a time, until every leaf is close enough to wood
+     * not to decay or {@code maxTendrils} have grown. Wood only ever gets added, so each leaf's nearest wood is found
+     * once and afterwards only compared against the newest tendril.
+     */
     public static void ensureLeavesSupported(TreeBlockCanvas canvas, int maxTendrils) {
-        for (int iter = 0; iter < maxTendrils; iter++) {
-            Map<TreeBlockCanvas.Vec, Integer> dist = TreePlausibility.computeDistances(canvas.getTrunk(), canvas.getLeaf());
-
-            TreeBlockCanvas.Vec worstLeaf = null;
-            TreeBlockCanvas.Vec worstWood = null;
-            int worstGap = -1;
-
-            for (TreeBlockCanvas.Vec leaf : new ArrayList<>(canvas.getLeaf())) {
-                Integer d = dist.get(leaf);
-                if (d != null && d <= LEGAL_DISTANCE) {
-                    continue;
-                }
-                TreeBlockCanvas.Vec nearest = null;
-                int best = Integer.MAX_VALUE;
-                for (TreeBlockCanvas.Vec wood : canvas.getTrunk()) {
-                    int cd = chebyshev(leaf, wood);
-                    if (cd < best) {
-                        best = cd;
-                        nearest = wood;
-                        if (cd <= 1) {
-                            break;
-                        }
-                    }
-                }
-                if (nearest != null && best > worstGap) {
-                    worstGap = best;
-                    worstLeaf = leaf;
-                    worstWood = nearest;
-                }
-            }
-
-            if (worstLeaf == null) {
-                return;
-            }
-            growTendril(canvas, worstWood, worstLeaf);
+        if (canvas.getTrunk().isEmpty()) {
+            return;
+        }
+        List<TreeBlockCanvas.Vec> unsupported = unsupportedLeaves(canvas);
+        Map<TreeBlockCanvas.Vec, Nearest> nearestWoodByLeaf = NearestWood.of(canvas.getTrunk()).nearestTo(unsupported);
+        for (int tendril = 0; tendril < maxTendrils && !unsupported.isEmpty(); tendril++) {
+            TreeBlockCanvas.Vec farthestLeaf = farthestFromWood(unsupported, nearestWoodByLeaf);
+            List<TreeBlockCanvas.Vec> tendrilWood = growTendril(canvas, nearestWoodByLeaf.get(farthestLeaf).wood(), farthestLeaf);
+            unsupported = unsupportedLeaves(canvas);
+            moveTowardNewWood(nearestWoodByLeaf, unsupported, tendrilWood);
         }
     }
 
-    private static void growTendril(TreeBlockCanvas canvas, TreeBlockCanvas.Vec from, TreeBlockCanvas.Vec to) {
+    private static List<TreeBlockCanvas.Vec> unsupportedLeaves(TreeBlockCanvas canvas) {
+        Map<TreeBlockCanvas.Vec, Integer> distance = TreePlausibility.computeDistances(canvas.getTrunk(), canvas.getLeaf());
+        List<TreeBlockCanvas.Vec> unsupported = new ArrayList<>();
+        for (TreeBlockCanvas.Vec leaf : canvas.getLeaf()) {
+            Integer d = distance.get(leaf);
+            if (d == null || d > LEGAL_DISTANCE) {
+                unsupported.add(leaf);
+            }
+        }
+        return unsupported;
+    }
+
+    private static TreeBlockCanvas.Vec farthestFromWood(List<TreeBlockCanvas.Vec> leaves, Map<TreeBlockCanvas.Vec, Nearest> nearestWoodByLeaf) {
+        TreeBlockCanvas.Vec farthest = null;
+        int farthestGap = -1;
+        for (TreeBlockCanvas.Vec leaf : leaves) {
+            int gap = nearestWoodByLeaf.get(leaf).distance();
+            if (gap > farthestGap) {
+                farthestGap = gap;
+                farthest = leaf;
+            }
+        }
+        return farthest;
+    }
+
+    private static void moveTowardNewWood(Map<TreeBlockCanvas.Vec, Nearest> nearestWoodByLeaf, List<TreeBlockCanvas.Vec> leaves,
+                                          List<TreeBlockCanvas.Vec> newWood) {
+        for (TreeBlockCanvas.Vec leaf : leaves) {
+            Nearest nearest = nearestWoodByLeaf.get(leaf);
+            for (TreeBlockCanvas.Vec wood : newWood) {
+                int distance = chebyshev(leaf, wood);
+                if (distance < nearest.distance()) {
+                    nearest = new Nearest(wood, distance);
+                }
+            }
+            nearestWoodByLeaf.put(leaf, nearest);
+        }
+    }
+
+    private static List<TreeBlockCanvas.Vec> growTendril(TreeBlockCanvas canvas, TreeBlockCanvas.Vec from, TreeBlockCanvas.Vec to) {
         int dx = to.x() - from.x();
         int dy = to.y() - from.y();
         int dz = to.z() - from.z();
@@ -75,16 +97,127 @@ public final class TreeSupport {
         int steps = Math.max(1, length - REACH_GAP);
         TreeBlockCanvas.Axis axis = TreeFunctions.logAxis(dx, dy, dz);
 
+        List<TreeBlockCanvas.Vec> grown = new ArrayList<>(steps);
         for (int i = 1; i <= steps; i++) {
             double t = i / (double) length;
             int x = from.x() + (int) Math.round(dx * t);
             int y = from.y() + (int) Math.round(dy * t);
             int z = from.z() + (int) Math.round(dz * t);
             canvas.setTrunk(x, y, z, TreeBlockCanvas.Role.TRUNK, axis);
+            grown.add(new TreeBlockCanvas.Vec(x, y, z));
         }
+        return grown;
     }
 
     private static int chebyshev(TreeBlockCanvas.Vec a, TreeBlockCanvas.Vec b) {
         return Math.max(Math.max(Math.abs(a.x() - b.x()), Math.abs(a.y() - b.y())), Math.abs(a.z() - b.z()));
     }
+
+    /**
+     * Finds the closest wood block to a leaf, by the largest of the x, y and z gaps, searching outward through a coarse
+     * grid of wood one shell of buckets at a time. Ties go to the wood that comes first in the trunk, as a plain scan
+     * would pick.
+     */
+    private static final class NearestWood {
+        private static final int BUCKET_SIZE_BLOCKS = 8;
+
+        private final Map<Long, List<Integer>> woodIndicesByBucket = new HashMap<>();
+        private final TreeBlockCanvas.Vec[] wood;
+        private int lowestBucket = Integer.MAX_VALUE;
+        private int highestBucket = Integer.MIN_VALUE;
+
+        private NearestWood(TreeBlockCanvas.Vec[] wood) {
+            this.wood = wood;
+            for (int index = 0; index < wood.length; index++) {
+                TreeBlockCanvas.Vec block = wood[index];
+                woodIndicesByBucket.computeIfAbsent(bucketKey(bucket(block.x()), bucket(block.y()), bucket(block.z())), ignored -> new ArrayList<>()).add(index);
+                for (int coordinate : new int[]{block.x(), block.y(), block.z()}) {
+                    lowestBucket = Math.min(lowestBucket, bucket(coordinate));
+                    highestBucket = Math.max(highestBucket, bucket(coordinate));
+                }
+            }
+        }
+
+        static NearestWood of(Set<TreeBlockCanvas.Vec> trunk) {
+            return new NearestWood(trunk.toArray(TreeBlockCanvas.Vec[]::new));
+        }
+
+        Map<TreeBlockCanvas.Vec, Nearest> nearestTo(List<TreeBlockCanvas.Vec> leaves) {
+            Map<TreeBlockCanvas.Vec, Nearest> nearestByLeaf = new HashMap<>();
+            for (TreeBlockCanvas.Vec leaf : leaves) {
+                nearestByLeaf.put(leaf, nearestTo(leaf));
+            }
+            return nearestByLeaf;
+        }
+
+        private Nearest nearestTo(TreeBlockCanvas.Vec leaf) {
+            int leafBucketX = bucket(leaf.x());
+            int leafBucketY = bucket(leaf.y());
+            int leafBucketZ = bucket(leaf.z());
+            Search search = new Search(leaf);
+            int lastRing = ringReachingAllWood(leafBucketX, leafBucketY, leafBucketZ);
+            for (int ring = 0; ring <= lastRing; ring++) {
+                for (int dx = -ring; dx <= ring; dx++) {
+                    for (int dy = -ring; dy <= ring; dy++) {
+                        boolean onShellAlready = Math.abs(dx) == ring || Math.abs(dy) == ring;
+                        int dzStep = onShellAlready || ring == 0 ? 1 : 2 * ring;
+                        for (int dz = -ring; dz <= ring; dz += dzStep) {
+                            search.consider(woodIndicesByBucket.get(bucketKey(leafBucketX + dx, leafBucketY + dy, leafBucketZ + dz)));
+                        }
+                    }
+                }
+                boolean fartherRingsCannotBeCloser = search.found() && search.bestDistance <= ring * BUCKET_SIZE_BLOCKS;
+                if (fartherRingsCannotBeCloser) {
+                    break;
+                }
+            }
+            return new Nearest(wood[search.bestIndex], search.bestDistance);
+        }
+
+        private int ringReachingAllWood(int... leafBuckets) {
+            int ring = 0;
+            for (int leafBucket : leafBuckets) {
+                ring = Math.max(ring, Math.max(Math.abs(leafBucket - lowestBucket), Math.abs(leafBucket - highestBucket)));
+            }
+            return ring;
+        }
+
+        private static int bucket(int coordinate) {
+            return Math.floorDiv(coordinate, BUCKET_SIZE_BLOCKS);
+        }
+
+        private static long bucketKey(int x, int y, int z) {
+            return ((long) x & 0x1FFFFF) | (((long) y & 0x1FFFFF) << 21) | (((long) z & 0x1FFFFF) << 42);
+        }
+
+        private final class Search {
+            private final TreeBlockCanvas.Vec leaf;
+            private int bestDistance = Integer.MAX_VALUE;
+            private int bestIndex = -1;
+
+            private Search(TreeBlockCanvas.Vec leaf) {
+                this.leaf = leaf;
+            }
+
+            void consider(List<Integer> woodIndices) {
+                if (woodIndices == null) {
+                    return;
+                }
+                for (int index : woodIndices) {
+                    int distance = chebyshev(leaf, wood[index]);
+                    if (distance < bestDistance || (distance == bestDistance && index < bestIndex)) {
+                        bestDistance = distance;
+                        bestIndex = index;
+                    }
+                }
+            }
+
+            boolean found() {
+                return bestIndex >= 0;
+            }
+        }
+    }
+
+    private record Nearest(TreeBlockCanvas.Vec wood, int distance) {
+    }
 }