minecraft-src/net/minecraft/world/level/lighting/ChunkSkyLightSources.java

package net.minecraft.world.level.lighting;

import net.minecraft.core.BlockPos;
import net.minecraft.core.Direction;
import net.minecraft.core.SectionPos;
import net.minecraft.util.BitStorage;
import net.minecraft.util.Mth;
import net.minecraft.util.SimpleBitStorage;
import net.minecraft.world.level.BlockGetter;
import net.minecraft.world.level.LevelHeightAccessor;
import net.minecraft.world.level.block.Blocks;
import net.minecraft.world.level.block.state.BlockState;
import net.minecraft.world.level.chunk.ChunkAccess;
import net.minecraft.world.level.chunk.LevelChunkSection;
import net.minecraft.world.phys.shapes.Shapes;
import net.minecraft.world.phys.shapes.VoxelShape;

public class ChunkSkyLightSources {
	private static final int SIZE = 16;
	public static final int NEGATIVE_INFINITY = Integer.MIN_VALUE;
	private final int minY;
	private final BitStorage heightmap;
	private final BlockPos.MutableBlockPos mutablePos1 = new BlockPos.MutableBlockPos();
	private final BlockPos.MutableBlockPos mutablePos2 = new BlockPos.MutableBlockPos();

	public ChunkSkyLightSources(LevelHeightAccessor level) {
		this.minY = level.getMinY() - 1;
		int i = level.getMaxY() + 1;
		int j = Mth.ceillog2(i - this.minY + 1);
		this.heightmap = new SimpleBitStorage(j, 256);
	}

	public void fillFrom(ChunkAccess chunk) {
		int i = chunk.getHighestFilledSectionIndex();
		if (i == -1) {
			this.fill(this.minY);
		} else {
			for (int j = 0; j < 16; j++) {
				for (int k = 0; k < 16; k++) {
					int l = Math.max(this.findLowestSourceY(chunk, i, k, j), this.minY);
					this.set(index(k, j), l);
				}
			}
		}
	}

	private int findLowestSourceY(ChunkAccess chunk, int sectionIndex, int x, int z) {
		int i = SectionPos.sectionToBlockCoord(chunk.getSectionYFromSectionIndex(sectionIndex) + 1);
		BlockPos.MutableBlockPos mutableBlockPos = this.mutablePos1.set(x, i, z);
		BlockPos.MutableBlockPos mutableBlockPos2 = this.mutablePos2.setWithOffset(mutableBlockPos, Direction.DOWN);
		BlockState blockState = Blocks.AIR.defaultBlockState();

		for (int j = sectionIndex; j >= 0; j--) {
			LevelChunkSection levelChunkSection = chunk.getSection(j);
			if (levelChunkSection.hasOnlyAir()) {
				blockState = Blocks.AIR.defaultBlockState();
				int k = chunk.getSectionYFromSectionIndex(j);
				mutableBlockPos.setY(SectionPos.sectionToBlockCoord(k));
				mutableBlockPos2.setY(mutableBlockPos.getY() - 1);
			} else {
				for (int k = 15; k >= 0; k--) {
					BlockState blockState2 = levelChunkSection.getBlockState(x, k, z);
					if (isEdgeOccluded(blockState, blockState2)) {
						return mutableBlockPos.getY();
					}

					blockState = blockState2;
					mutableBlockPos.set(mutableBlockPos2);
					mutableBlockPos2.move(Direction.DOWN);
				}
			}
		}

		return this.minY;
	}

	public boolean update(BlockGetter level, int x, int y, int z) {
		int i = y + 1;
		int j = index(x, z);
		int k = this.get(j);
		if (i < k) {
			return false;
		} else {
			BlockPos blockPos = this.mutablePos1.set(x, y + 1, z);
			BlockState blockState = level.getBlockState(blockPos);
			BlockPos blockPos2 = this.mutablePos2.set(x, y, z);
			BlockState blockState2 = level.getBlockState(blockPos2);
			if (this.updateEdge(level, j, k, blockPos, blockState, blockPos2, blockState2)) {
				return true;
			} else {
				BlockPos blockPos3 = this.mutablePos1.set(x, y - 1, z);
				BlockState blockState3 = level.getBlockState(blockPos3);
				return this.updateEdge(level, j, k, blockPos2, blockState2, blockPos3, blockState3);
			}
		}
	}

	private boolean updateEdge(BlockGetter level, int index, int minY, BlockPos pos1, BlockState state1, BlockPos pos2, BlockState state2) {
		int i = pos1.getY();
		if (isEdgeOccluded(state1, state2)) {
			if (i > minY) {
				this.set(index, i);
				return true;
			}
		} else if (i == minY) {
			this.set(index, this.findLowestSourceBelow(level, pos2, state2));
			return true;
		}

		return false;
	}

	private int findLowestSourceBelow(BlockGetter level, BlockPos pos, BlockState state) {
		BlockPos.MutableBlockPos mutableBlockPos = this.mutablePos1.set(pos);
		BlockPos.MutableBlockPos mutableBlockPos2 = this.mutablePos2.setWithOffset(pos, Direction.DOWN);
		BlockState blockState = state;

		while (mutableBlockPos2.getY() >= this.minY) {
			BlockState blockState2 = level.getBlockState(mutableBlockPos2);
			if (isEdgeOccluded(blockState, blockState2)) {
				return mutableBlockPos.getY();
			}

			blockState = blockState2;
			mutableBlockPos.set(mutableBlockPos2);
			mutableBlockPos2.move(Direction.DOWN);
		}

		return this.minY;
	}

	private static boolean isEdgeOccluded(BlockState state1, BlockState state2) {
		if (state2.getLightBlock() != 0) {
			return true;
		} else {
			VoxelShape voxelShape = LightEngine.getOcclusionShape(state1, Direction.DOWN);
			VoxelShape voxelShape2 = LightEngine.getOcclusionShape(state2, Direction.UP);
			return Shapes.faceShapeOccludes(voxelShape, voxelShape2);
		}
	}

	public int getLowestSourceY(int x, int z) {
		int i = this.get(index(x, z));
		return this.extendSourcesBelowWorld(i);
	}

	public int getHighestLowestSourceY() {
		int i = Integer.MIN_VALUE;

		for (int j = 0; j < this.heightmap.getSize(); j++) {
			int k = this.heightmap.get(j);
			if (k > i) {
				i = k;
			}
		}

		return this.extendSourcesBelowWorld(i + this.minY);
	}

	private void fill(int value) {
		int i = value - this.minY;

		for (int j = 0; j < this.heightmap.getSize(); j++) {
			this.heightmap.set(j, i);
		}
	}

	private void set(int index, int value) {
		this.heightmap.set(index, value - this.minY);
	}

	private int get(int index) {
		return this.heightmap.get(index) + this.minY;
	}

	private int extendSourcesBelowWorld(int y) {
		return y == this.minY ? Integer.MIN_VALUE : y;
	}

	private static int index(int x, int z) {
		return x + z * 16;
	}
}