Item entities

client/entity/item_entity.ts

@@ -0,0 +1,83 @@
+import { ItemStack } from "$/common/inventory.ts";
+import type { EntityInfo } from "$/common/protocol.ts";
+import type { ClientLevel } from "../level/client_level.ts";
+import { Entity } from "./entity.ts";
+
+// how many ticks a server position takes to reach, like minecraft's lerpTo
+const LERP_TICKS = 3;
+// how many ticks it takes to fly into whoever picked it up
+const PICKUP_TICKS = 3;
+
+// an item lying on the ground. the server simulates it, this only moves where it's told and spins
+export class ItemEntity extends Entity {
+	item: ItemStack;
+	// ticks since it showed up, for spinning and bobbing
+	age = 0;
+	// so items dropped together don't spin in step
+	readonly bob_offset = Math.random() * Math.PI * 2;
+
+	#target_x: number;
+	#target_y: number;
+	#target_z: number;
+	#lerp_ticks = 0;
+
+	// who's picking it up, and for how many ticks it has been flying to them
+	#picked_up_by: Entity | undefined;
+	#pickup_age = 0;
+
+	constructor(level: ClientLevel, info: EntityInfo) {
+		super(level, info.id, 0.25, 0.25, 0.125);
+		this.item = ItemStack.from_data(info.item);
+		this.set_position(info.x, info.y, info.z);
+		this.#target_x = info.x;
+		this.#target_y = info.y;
+		this.#target_z = info.z;
+	}
+
+	lerp_to(x: number, y: number, z: number) {
+		this.#target_x = x;
+		this.#target_y = y;
+		this.#target_z = z;
+		this.#lerp_ticks = LERP_TICKS;
+	}
+
+	// it already went into their inventory on the server, this is only the animation
+	pick_up(by: Entity) {
+		this.#picked_up_by = by;
+	}
+
+	tick() {
+		this.age += 1;
+
+		if (this.#picked_up_by) {
+			this.#pickup_age += 1;
+			if (this.#pickup_age >= PICKUP_TICKS) {
+				this.level.remove_entity(this.id);
+			}
+			return;
+		}
+
+		if (this.#lerp_ticks > 0) {
+			this.x += (this.#target_x - this.x) / this.#lerp_ticks;
+			this.y += (this.#target_y - this.y) / this.#lerp_ticks;
+			this.z += (this.#target_z - this.z) / this.#lerp_ticks;
+			this.#lerp_ticks -= 1;
+		}
+	}
+
+	// while being picked up it speeds towards the middle of whoever took it, like minecraft's ItemPickupParticle
+	override render_position(partial_tick: number) {
+		const position = super.render_position(partial_tick);
+		const by = this.#picked_up_by;
+		if (!by) {
+			return position;
+		}
+		const target = by.render_position(partial_tick);
+		const t = Math.min(1, (this.#pickup_age + partial_tick) / PICKUP_TICKS) ** 2;
+		return {
+			x: position.x + (target.x - position.x) * t,
+			y: position.y + (target.y + 0.5 - position.y) * t,
+			z: position.z + (target.z - position.z) * t,
+		};
+	}
+}