feat(client): gun pipper with ground impact point and radar lead marker

Draws where the shells of the first light autocannon come down and, for the
selected radar target, a lead pipper. Uses the same ballistics as Warium's
LACFireScript (muzzle speed, barrels, drag 0.99, gravity 0.05).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YVREx3uo7nz1FEhzveWTUh

src/main/java/dev/lumareth/improvedAerodynamics/client/pipper/GunFinder.java

@@ -0,0 +1,155 @@
+package dev.lumareth.improvedAerodynamics.client.pipper;
+
+import net.minecraft.client.multiplayer.ClientLevel;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.tags.TagKey;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.DirectionProperty;
+import net.minecraft.world.level.block.state.properties.Property;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraftforge.fml.ModList;
+import net.minecraftforge.registries.ForgeRegistries;
+import org.joml.primitives.AABBic;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Finds the light autocannon of a ship and works out what it will shoot, the same way Warium's LACFireScript does:
+ * barrel count, muzzle, aim direction and muzzle speed.
+ */
+final class GunFinder {
+    private static final ResourceLocation LIGHT_AUTOCANNON = new ResourceLocation("crusty_chunks", "light_autocannon");
+    private static final TagKey<Block> BARREL = TagKey.create(Registries.BLOCK, new ResourceLocation("crusty_chunks", "acbarrel"));
+    private static final TagKey<Block> PASSTHROUGH = TagKey.create(Registries.BLOCK, new ResourceLocation("crusty_chunks", "barrelpassthrough"));
+    private static final int RESCAN_TICKS = 100;
+    private static final int MAX_GUNS = 16;
+
+    /** Muzzle and direction in ship space and the speed of the shell in blocks per tick. */
+    record Shot(double mx, double my, double mz, double dx, double dy, double dz, double speed) {
+    }
+
+    private long shipId = Long.MIN_VALUE;
+    private long lastScan = Long.MIN_VALUE;
+    private final List<BlockPos> guns = new ArrayList<>();
+
+    /** The gun closest to the seat, or null if the ship has none loaded. */
+    Shot find(ClientLevel level, long shipId, AABBic aabb, BlockPos seat) {
+        if (shipId != this.shipId || level.getGameTime() - lastScan >= RESCAN_TICKS || level.getGameTime() < lastScan) {
+            this.shipId = shipId;
+            lastScan = level.getGameTime();
+            scan(level, aabb);
+        }
+        BlockPos best = null;
+        double bestDistance = Double.MAX_VALUE;
+        for (BlockPos pos : guns) {
+            double distance = pos.distSqr(seat);
+            if (distance < bestDistance) {
+                bestDistance = distance;
+                best = pos;
+            }
+        }
+        return best == null ? null : shotOf(level, best);
+    }
+
+    private void scan(ClientLevel level, AABBic aabb) {
+        guns.clear();
+        Block gun = ForgeRegistries.BLOCKS.getValue(LIGHT_AUTOCANNON);
+        if (gun == null || aabb == null) {
+            return;
+        }
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        for (int cx = aabb.minX() >> 4; cx <= aabb.maxX() >> 4; cx++) {
+            for (int cz = aabb.minZ() >> 4; cz <= aabb.maxZ() >> 4; cz++) {
+                ChunkAccess chunk = level.getChunk(cx, cz, ChunkStatus.FULL, false);
+                if (chunk == null) {
+                    continue;
+                }
+                LevelChunkSection[] sections = chunk.getSections();
+                for (int i = 0; i < sections.length; i++) {
+                    LevelChunkSection section = sections[i];
+                    if (section.hasOnlyAir() || !section.maybeHas(state -> state.is(gun))) {
+                        continue;
+                    }
+                    int baseY = level.getSectionYFromSectionIndex(i) << 4;
+                    for (int x = 0; x < 16; x++) {
+                        for (int y = 0; y < 16; y++) {
+                            for (int z = 0; z < 16; z++) {
+                                if (section.getBlockState(x, y, z).is(gun) && guns.size() < MAX_GUNS) {
+                                    guns.add(pos.set((cx << 4) + x, baseY + y, (cz << 4) + z).immutable());
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    private static Shot shotOf(ClientLevel level, BlockPos gun) {
+        BlockState state = level.getBlockState(gun);
+        Property<?> property = state.getBlock().getStateDefinition().getProperty("facing");
+        if (!(property instanceof DirectionProperty facingProperty)) {
+            return null;
+        }
+        Direction facing = state.getValue(facingProperty);
+        int fx = facing.getStepX();
+        int fy = facing.getStepY();
+        int fz = facing.getStepZ();
+
+        // Barrels, counted like Warium does: up to five more behind the first one
+        double barrels = 1.0;
+        for (int i = 0; i < 5 && level.getBlockState(gun.offset(fx * (int) (1 + barrels), fy * (int) (1 + barrels), fz * (int) (1 + barrels))).is(BARREL); i++) {
+            barrels++;
+        }
+        // Muzzle: past the barrels, skipping through blocks the shell passes
+        double position = barrels;
+        for (int i = 0; i < 10; i++) {
+            BlockState at = level.getBlockState(gun.offset(fx * (int) (1 + position), fy * (int) (1 + position), fz * (int) (1 + position)));
+            if ((!at.isAir() && !at.canOcclude()) || at.is(PASSTHROUGH)) {
+                position++;
+            } else {
+                break;
+            }
+        }
+        double mx = gun.getX() + fx * (1.5 + position) + 0.5;
+        double my = gun.getY() + fy * (1.5 + position) + 0.5;
+        double mz = gun.getZ() + fz * (1.5 + position) + 0.5;
+
+        // Aim, from the tags of the gun itself
+        double aimX = 0.0;
+        double aimY = 0.0;
+        double aimZ = 0.0;
+        BlockEntity entity = level.getBlockEntity(gun);
+        double gx = entity == null ? 0.0 : entity.getPersistentData().getDouble("X");
+        double gz = entity == null ? 0.0 : entity.getPersistentData().getDouble("Z");
+        double gpitch = entity == null ? 0.0 : entity.getPersistentData().getDouble("Pitch");
+        if (1.0 > Math.abs(fx - gx) || 1.0 > Math.abs(fz - gz)) {
+            aimY = gpitch;
+            aimX = gx + fx;
+            aimZ = gz + fz;
+        }
+        if (aimX * aimZ == 0.0) {
+            aimX = fx;
+            aimZ = fz;
+        }
+        double length = Math.sqrt(aimX * aimX + aimY * aimY + aimZ * aimZ);
+        if (length < 1.0E-6) {
+            return null;
+        }
+
+        double speed = PipperConfig.MUZZLE_SPEED_OVERRIDE.get();
+        if (speed <= 0.0) {
+            double multiplier = ModList.get().isLoaded("ritchiesprojectilelib") ? 2.0 : 1.0;
+            speed = (5.0 + barrels / 1.5) * multiplier;
+        }
+        return new Shot(mx, my, mz, aimX / length, aimY / length, aimZ / length, speed);
+    }
+}