SkyLightUpdateCubeSelector.java

/*
 *  This file is part of Cubic Chunks Mod, licensed under the MIT License (MIT).
 *
 *  Copyright (c) 2015 contributors
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included in
 *  all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 *  THE SOFTWARE.
 */
package cubicchunks.lighting;

import com.carrotsearch.hppc.IntHashSet;
import com.carrotsearch.hppc.IntSet;

import net.minecraft.util.math.BlockPos;
import net.minecraft.world.EnumSkyBlock;
import net.minecraft.world.World;

import cubicchunks.util.Coords;
import cubicchunks.world.column.Column;
import cubicchunks.world.cube.Cube;

class SkyLightUpdateCubeSelector {

	private SkyLightUpdateCubeSelector() {
		throw new RuntimeException();
	}

	/**
	 * Returns Set of cube Y locations that can be updated for give light update.
	 *
	 * @param column Column to select cubes from
	 * @param localX in-column X position
	 * @param localZ in-column Z position
	 * @param minBlockY minimum light update Y. Integer.MIN_VALUE for no lower limit.
	 * @param maxBlockY position from which updating should be started. Integer.MAX_VALUE tu update from top of the
	 * world.
	 *
	 * @return set of affected cube Y positions
	 */
	static IntSet getCubesY(Column column, int localX, int localZ, int minBlockY, int maxBlockY) {
		// NOTE: maxBlockY is always the air block above the top block that was added or removed
		World world = column.getWorld();

		IntSet cubesToDiffuse = new IntHashSet();

		if (world.provider.getHasNoSky()) {
			return cubesToDiffuse;
		}

		BlockPos.MutableBlockPos blockPos = new BlockPos.MutableBlockPos(
			Coords.localToBlock(column.xPosition, localX),
			maxBlockY - 1,
			Coords.localToBlock(column.zPosition, localZ)
		);

		int newMaxBlockY = column.getHeightValue(localX, localZ);

		//if there is no min block - there are no blocks here
		//so assume it's at Integer.MIN_VALUE
		int maxCubeY = Coords.blockToCube(newMaxBlockY);

		//attempt to update lighting only in loaded cubes
		for (Cube cube : column.getLoadedCubes()) {
			int cubeY = cube.getY();
			int minCubeBlockY = cubeY*16;

			//do we even need to do anything here?
			if (maxBlockY < minCubeBlockY) {
				continue;
			}
			if (cubeY > maxCubeY) {
				//if light value at the bottom is already correct - nothing to do here
				//so update only if incorrect
				blockPos.setPos(localX, 0, localZ);
				if (cube.getLightFor(EnumSkyBlock.SKY, blockPos) != 15) {
					cubesToDiffuse.add(cube.getY());
				}
			} else if (cubeY == maxCubeY) {
				//current top block is the actual reason to update
				//so cube that contains it needs update
				cubesToDiffuse.add(cube.getY());
				//light can propagate to cube below too
				if ((cube = column.getLoadedCube(maxCubeY - 1)) != null) {
					cubesToDiffuse.add(cube.getY());
				}
			} else if (cubeY == maxCubeY - 1) {
				//it's handled by cubeY == maxCubeY case
				continue;
			} else {
				assert cubeY < maxCubeY - 1;
				blockPos.setPos(localX, 15, localZ);
				//if we are below minBlockY or if the top block has correct light value (0) - nothing to do
				if (minCubeBlockY + 15 < minBlockY || cube.getLightFor(EnumSkyBlock.SKY, blockPos) == 0) {
					continue;
				}
				cubesToDiffuse.add(cube.getY());
			}
		}

		return cubesToDiffuse;
	}
}