--- a/net/minecraft/data/worldgen/SurfaceRuleData.java
+++ b/net/minecraft/data/worldgen/SurfaceRuleData.java
@@ -53,6 +53,66 @@
         return overworldLike(true, false, true);
     }
 
+    // Paper start
+    // Taken from SurfaceRules$VerticalGradientConditionSource
+    // isRoof = true if roof, false if floor
+    public record PaperBedrockConditionSource(net.minecraft.resources.ResourceLocation randomName, VerticalAnchor trueAtAndBelow, VerticalAnchor falseAtAndAbove, boolean isRoof) implements SurfaceRules.ConditionSource {
+
+        public static final net.minecraft.util.KeyDispatchDataCodec<PaperBedrockConditionSource> CODEC = net.minecraft.util.KeyDispatchDataCodec.of(com.mojang.serialization.codecs.RecordCodecBuilder.<PaperBedrockConditionSource>mapCodec((instance) -> {
+            return instance.group(
+                net.minecraft.resources.ResourceLocation.CODEC.fieldOf("random_name").forGetter(PaperBedrockConditionSource::randomName),
+                VerticalAnchor.CODEC.fieldOf("true_at_and_below").forGetter(PaperBedrockConditionSource::trueAtAndBelow),
+                VerticalAnchor.CODEC.fieldOf("false_at_and_above").forGetter(PaperBedrockConditionSource::falseAtAndAbove),
+                com.mojang.serialization.Codec.BOOL.fieldOf("roof").forGetter(PaperBedrockConditionSource::isRoof)
+                ).apply(instance, PaperBedrockConditionSource::new);
+        }));
+
+        public PaperBedrockConditionSource(String randomName, net.minecraft.world.level.levelgen.VerticalAnchor trueAtAndBelow, net.minecraft.world.level.levelgen.VerticalAnchor falseAtAndAbove, boolean invert) {
+            this(new net.minecraft.resources.ResourceLocation(randomName), trueAtAndBelow, falseAtAndAbove, invert);
+        }
+
+        @Override
+        public net.minecraft.util.KeyDispatchDataCodec<PaperBedrockConditionSource>codec() {
+            return CODEC;
+        }
+
+        @Override
+        public SurfaceRules.Condition apply(SurfaceRules.Context context) {
+            boolean hasFlatBedrock = context.context.getWorld().paperConfig().environment.generateFlatBedrock;
+            int trueAtY = this.trueAtAndBelow().resolveY(context.context);
+            int falseAtY = this.falseAtAndAbove().resolveY(context.context);
+
+            int y = isRoof ? Math.max(falseAtY, trueAtY) - 1 : Math.min(falseAtY, trueAtY) ;
+            final int i = hasFlatBedrock ? y : trueAtY;
+            final int j = hasFlatBedrock ? y : falseAtY;
+            // TODO access transformer for randomState
+            final net.minecraft.world.level.levelgen.PositionalRandomFactory positionalRandomFactory = context.randomState.getOrCreateRandomFactory(this.randomName());
+
+            class VerticalGradientCondition extends SurfaceRules.LazyYCondition {
+                VerticalGradientCondition(SurfaceRules.Context context) {
+                    super(context);
+                }
+
+                @Override
+                protected boolean compute() {
+                    int y = this.context.blockY;
+                    if (y <= i) {
+                        return true;
+                    } else if (y >= j) {
+                        return false;
+                    } else {
+                        double d = net.minecraft.util.Mth.map((double) y, (double) i, (double) j, 1.0D, 0.0D);
+                        net.minecraft.util.RandomSource randomSource = positionalRandomFactory.at(this.context.blockX, i, this.context.blockZ);
+                        return (double) randomSource.nextFloat() < d;
+                    }
+                }
+            }
+
+            return new VerticalGradientCondition(context);
+        }
+    }
+    // Paper end
+
     public static SurfaceRules.RuleSource overworldLike(boolean surface, boolean bedrockRoof, boolean bedrockFloor) {
         SurfaceRules.ConditionSource conditionSource = SurfaceRules.yBlockCheck(VerticalAnchor.absolute(97), 2);
         SurfaceRules.ConditionSource conditionSource2 = SurfaceRules.yBlockCheck(VerticalAnchor.absolute(256), 0);
@@ -83,11 +143,11 @@
         SurfaceRules.RuleSource ruleSource9 = SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.WOODED_BADLANDS), SurfaceRules.ifTrue(conditionSource, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource16, COARSE_DIRT), SurfaceRules.ifTrue(conditionSource17, COARSE_DIRT), SurfaceRules.ifTrue(conditionSource18, COARSE_DIRT), ruleSource))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.SWAMP), SurfaceRules.ifTrue(conditionSource6, SurfaceRules.ifTrue(SurfaceRules.not(conditionSource7), SurfaceRules.ifTrue(SurfaceRules.noiseCondition(Noises.SWAMP, 0.0D), WATER)))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.MANGROVE_SWAMP), SurfaceRules.ifTrue(conditionSource5, SurfaceRules.ifTrue(SurfaceRules.not(conditionSource7), SurfaceRules.ifTrue(SurfaceRules.noiseCondition(Noises.SWAMP, 0.0D), WATER)))))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.BADLANDS, Biomes.ERODED_BADLANDS, Biomes.WOODED_BADLANDS), SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource2, ORANGE_TERRACOTTA), SurfaceRules.ifTrue(conditionSource4, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource16, TERRACOTTA), SurfaceRules.ifTrue(conditionSource17, TERRACOTTA), SurfaceRules.ifTrue(conditionSource18, TERRACOTTA), SurfaceRules.bandlands())), SurfaceRules.ifTrue(conditionSource8, SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.ON_CEILING, RED_SANDSTONE), RED_SAND)), SurfaceRules.ifTrue(SurfaceRules.not(conditionSource11), ORANGE_TERRACOTTA), SurfaceRules.ifTrue(conditionSource10, WHITE_TERRACOTTA), ruleSource3)), SurfaceRules.ifTrue(conditionSource3, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource7, SurfaceRules.ifTrue(SurfaceRules.not(conditionSource4), ORANGE_TERRACOTTA)), SurfaceRules.bandlands())), SurfaceRules.ifTrue(SurfaceRules.UNDER_FLOOR, SurfaceRules.ifTrue(conditionSource10, WHITE_TERRACOTTA)))), SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.ifTrue(conditionSource8, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource12, SurfaceRules.ifTrue(conditionSource11, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource9, AIR), SurfaceRules.ifTrue(SurfaceRules.temperature(), ICE), WATER))), ruleSource8))), SurfaceRules.ifTrue(conditionSource10, SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.ifTrue(conditionSource12, SurfaceRules.ifTrue(conditionSource11, WATER))), SurfaceRules.ifTrue(SurfaceRules.UNDER_FLOOR, ruleSource7), SurfaceRules.ifTrue(conditionSource14, SurfaceRules.ifTrue(SurfaceRules.DEEP_UNDER_FLOOR, SANDSTONE)), SurfaceRules.ifTrue(conditionSource15, SurfaceRules.ifTrue(SurfaceRules.VERY_DEEP_UNDER_FLOOR, SANDSTONE)))), SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.FROZEN_PEAKS, Biomes.JAGGED_PEAKS), STONE), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.WARM_OCEAN, Biomes.LUKEWARM_OCEAN, Biomes.DEEP_LUKEWARM_OCEAN), ruleSource2), ruleSource3)));
         ImmutableList.Builder<SurfaceRules.RuleSource> builder = ImmutableList.builder();
         if (bedrockRoof) {
-            builder.add(SurfaceRules.ifTrue(SurfaceRules.not(SurfaceRules.verticalGradient("bedrock_roof", VerticalAnchor.belowTop(5), VerticalAnchor.top())), BEDROCK));
+            builder.add(SurfaceRules.ifTrue(SurfaceRules.not(new PaperBedrockConditionSource("bedrock_roof", VerticalAnchor.belowTop(5), VerticalAnchor.top(), true)), BEDROCK)); // Paper
         }
 
         if (bedrockFloor) {
-            builder.add(SurfaceRules.ifTrue(SurfaceRules.verticalGradient("bedrock_floor", VerticalAnchor.bottom(), VerticalAnchor.aboveBottom(5)), BEDROCK));
+            builder.add(SurfaceRules.ifTrue(new PaperBedrockConditionSource("bedrock_floor", VerticalAnchor.bottom(), VerticalAnchor.aboveBottom(5), false), BEDROCK)); // Paper
         }
 
         SurfaceRules.RuleSource ruleSource10 = SurfaceRules.ifTrue(SurfaceRules.abovePreliminarySurface(), ruleSource9);
@@ -112,7 +172,7 @@
         SurfaceRules.ConditionSource conditionSource11 = SurfaceRules.noiseCondition(Noises.NETHER_WART, 1.17D);
         SurfaceRules.ConditionSource conditionSource12 = SurfaceRules.noiseCondition(Noises.NETHER_STATE_SELECTOR, 0.0D);
         SurfaceRules.RuleSource ruleSource = SurfaceRules.ifTrue(conditionSource9, SurfaceRules.ifTrue(conditionSource3, SurfaceRules.ifTrue(conditionSource4, GRAVEL)));
-        return SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.verticalGradient("bedrock_floor", VerticalAnchor.bottom(), VerticalAnchor.aboveBottom(5)), BEDROCK), SurfaceRules.ifTrue(SurfaceRules.not(SurfaceRules.verticalGradient("bedrock_roof", VerticalAnchor.belowTop(5), VerticalAnchor.top())), BEDROCK), SurfaceRules.ifTrue(conditionSource5, NETHERRACK), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.BASALT_DELTAS), SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.UNDER_CEILING, BASALT), SurfaceRules.ifTrue(SurfaceRules.UNDER_FLOOR, SurfaceRules.sequence(ruleSource, SurfaceRules.ifTrue(conditionSource12, BASALT), BLACKSTONE)))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.SOUL_SAND_VALLEY), SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.UNDER_CEILING, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource12, SOUL_SAND), SOUL_SOIL)), SurfaceRules.ifTrue(SurfaceRules.UNDER_FLOOR, SurfaceRules.sequence(ruleSource, SurfaceRules.ifTrue(conditionSource12, SOUL_SAND), SOUL_SOIL)))), SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.not(conditionSource2), SurfaceRules.ifTrue(conditionSource6, LAVA)), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.WARPED_FOREST), SurfaceRules.ifTrue(SurfaceRules.not(conditionSource10), SurfaceRules.ifTrue(conditionSource, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource11, WARPED_WART_BLOCK), WARPED_NYLIUM)))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.CRIMSON_FOREST), SurfaceRules.ifTrue(SurfaceRules.not(conditionSource10), SurfaceRules.ifTrue(conditionSource, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource11, NETHER_WART_BLOCK), CRIMSON_NYLIUM)))))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.NETHER_WASTES), SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.UNDER_FLOOR, SurfaceRules.ifTrue(conditionSource7, SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.not(conditionSource6), SurfaceRules.ifTrue(conditionSource3, SurfaceRules.ifTrue(conditionSource4, SOUL_SAND))), NETHERRACK))), SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.ifTrue(conditionSource, SurfaceRules.ifTrue(conditionSource4, SurfaceRules.ifTrue(conditionSource8, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource2, GRAVEL), SurfaceRules.ifTrue(SurfaceRules.not(conditionSource6), GRAVEL)))))))), NETHERRACK);
+        return SurfaceRules.sequence(SurfaceRules.ifTrue(new PaperBedrockConditionSource("bedrock_floor", VerticalAnchor.bottom(), VerticalAnchor.aboveBottom(5), false), BEDROCK), SurfaceRules.ifTrue(SurfaceRules.not(new PaperBedrockConditionSource("bedrock_roof", VerticalAnchor.belowTop(5), VerticalAnchor.top(), true)), BEDROCK), SurfaceRules.ifTrue(conditionSource5, NETHERRACK), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.BASALT_DELTAS), SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.UNDER_CEILING, BASALT), SurfaceRules.ifTrue(SurfaceRules.UNDER_FLOOR, SurfaceRules.sequence(ruleSource, SurfaceRules.ifTrue(conditionSource12, BASALT), BLACKSTONE)))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.SOUL_SAND_VALLEY), SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.UNDER_CEILING, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource12, SOUL_SAND), SOUL_SOIL)), SurfaceRules.ifTrue(SurfaceRules.UNDER_FLOOR, SurfaceRules.sequence(ruleSource, SurfaceRules.ifTrue(conditionSource12, SOUL_SAND), SOUL_SOIL)))), SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.not(conditionSource2), SurfaceRules.ifTrue(conditionSource6, LAVA)), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.WARPED_FOREST), SurfaceRules.ifTrue(SurfaceRules.not(conditionSource10), SurfaceRules.ifTrue(conditionSource, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource11, WARPED_WART_BLOCK), WARPED_NYLIUM)))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.CRIMSON_FOREST), SurfaceRules.ifTrue(SurfaceRules.not(conditionSource10), SurfaceRules.ifTrue(conditionSource, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource11, NETHER_WART_BLOCK), CRIMSON_NYLIUM)))))), SurfaceRules.ifTrue(SurfaceRules.isBiome(Biomes.NETHER_WASTES), SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.UNDER_FLOOR, SurfaceRules.ifTrue(conditionSource7, SurfaceRules.sequence(SurfaceRules.ifTrue(SurfaceRules.not(conditionSource6), SurfaceRules.ifTrue(conditionSource3, SurfaceRules.ifTrue(conditionSource4, SOUL_SAND))), NETHERRACK))), SurfaceRules.ifTrue(SurfaceRules.ON_FLOOR, SurfaceRules.ifTrue(conditionSource, SurfaceRules.ifTrue(conditionSource4, SurfaceRules.ifTrue(conditionSource8, SurfaceRules.sequence(SurfaceRules.ifTrue(conditionSource2, GRAVEL), SurfaceRules.ifTrue(SurfaceRules.not(conditionSource6), GRAVEL)))))))), NETHERRACK);
     }
 
     public static SurfaceRules.RuleSource end() {
