BauSystem2.0/BauSystem_Main/src/de/steamwar/bausystem/utils/RayTraceUtils.java

/*
 * This file is a part of the SteamWar software.
 *
 * Copyright (C) 2022  SteamWar.de-Serverteam
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

package de.steamwar.bausystem.utils;

import lombok.experimental.UtilityClass;
import org.bukkit.FluidCollisionMode;
import org.bukkit.GameMode;
import org.bukkit.Location;
import org.bukkit.entity.Entity;
import org.bukkit.entity.Player;
import org.bukkit.util.BoundingBox;
import org.bukkit.util.RayTraceResult;
import org.bukkit.util.Vector;

import java.util.List;

@UtilityClass
public class RayTraceUtils {

    public static RayTraceResult trace(Player player, Location to, List<Entity> entityList) {
        if (player.getGameMode() == GameMode.SPECTATOR) {
            return null;
        }

        Location startPos = to.clone().add(0.0, player.getEyeHeight(), 0.0);
        Vector direction = to.getDirection();
        RayTraceResult blocks = player.getWorld().rayTraceBlocks(startPos, direction, 10.0, FluidCollisionMode.NEVER, true);

        Entity nearestHitEntity = null;
        RayTraceResult nearestHitResult = null;
        double nearestDistanceSq = Double.MAX_VALUE;
        for (Entity entity : entityList) {
            BoundingBox boundingBox = entity.getBoundingBox();
            RayTraceResult hitResult = boundingBox.rayTrace(startPos.toVector(), direction, 10.0);
            if (hitResult != null) {
                double distanceSq = startPos.toVector().distanceSquared(hitResult.getHitPosition());
                if (distanceSq < nearestDistanceSq) {
                    nearestHitEntity = entity;
                    nearestHitResult = hitResult;
                    nearestDistanceSq = distanceSq;
                }
            }
        }
        RayTraceResult entities = nearestHitEntity == null ? null : new RayTraceResult(nearestHitResult.getHitPosition(), nearestHitEntity, nearestHitResult.getHitBlockFace());

        if (blocks == null) {
            return entities;
        } else if (entities == null) {
            return blocks;
        } else {
            Vector startVec = startPos.toVector();
            double blockHitDistance = startVec.distance(blocks.getHitPosition());
            double entityHitDistanceSquared = startVec.distanceSquared(entities.getHitPosition());
            return entityHitDistanceSquared < blockHitDistance * blockHitDistance ? entities : blocks;
        }
    }

    public static boolean isOccluded(Vector a, Vector n, Vector b) {
        // a = Head pos, n = View direction (normalized), b = entity center
        // https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line#Vector_formulation

        double abX = b.getX() - a.getX();
        double abY = b.getY() - a.getY();
        double abZ = b.getZ() - a.getZ();
        double lambda = abX * n.getX() + abY * n.getY() + abZ * n.getZ();
        double distX = abX - n.getX() * lambda;
        double distY = abY - n.getY() * lambda;
        double distZ = abZ - n.getZ() * lambda;
        return Math.abs(distX) < 0.5 && Math.abs(distY) < 0.5 && Math.abs(distZ) < 0.5;
    }
}