Basic crops system

MODS.md

@@ -20,6 +20,7 @@ too, since the client is already a web page.
 - [Identifiers](#identifiers)
 - [Textures](#textures)
 - [Blocks](#blocks)
+- [Block models](#block-models)
 - [Items](#items)
 - [Recipes](#recipes)
 - [Server scripts](#server-scripts)
@@ -89,6 +90,7 @@ mods/
   copper_tools/
     manifest.json
     blocks/*.json
+    models/*.json
     items/*.json
     recipes/*.json
     worldgen/ores.json
@@ -194,7 +196,9 @@ program**, so the server and each client can number blocks differently. Saves an
 | Field                  | Default     | Maps to `BlockRegistry` | Meaning                                                                                      |
 | ---------------------- | ----------- | ----------------------- | -------------------------------------------------------------------------------------------- |
 | `id`                   | required    | `id`                    | The block's id.                                                                              |
-| `textures`             | required    | `textures`              | One texture id, `{ top, bottom, side }` or `{ front, side }`.                                |
+| `textures`             | required    | `textures`              | One texture id, `{ top, bottom, side }` or `{ front, side }`. With another `model`, the model's texture variables, like `{ "crop": "..." }`. |
+| `model`                | `engine:cube` | `model`               | The [block model](#block-models).                                                            |
+| `variants`             | none        | `variants`              | A different `model`, `textures` or `y` rotation for some states, see [block models](#block-models). |
 | `render_layer`         | `solid`     | `render_layer`          | `solid`, `cutout` (texels fully opaque or fully clear, like leaves) or `translucent` (blended, like water and glass). Non-solid blocks don't hide their neighbors' faces. |
 | `cull_same`            | see meaning | `cull_same`             | Hide faces between two of this block. Defaults to `true` for translucent blocks, `false` otherwise. |
 | `light_emission`       | `0`         | `light_emission`        | Light level 0-15 it gives off, like a torch (14). |
@@ -216,8 +220,84 @@ functions.
 
 Block states are declared like `[{ "name": "facing", "bits": 2, "default": 0 }]`, at most 16 bits in total. A block
 starts with its defaults when it's placed or generated, and server scripts read and change them with
-`ctx.world.get_state` / `set_state`. States are saved with the world and synced to players. They can't change textures
-yet, because the mesher ignores them. `variants` is reserved for that.
+`ctx.world.get_state` / `set_state`. States are saved with the world and synced to players. `variants` changes how the
+block looks with them.
+
+## Block models
+
+A block's shape comes from its model, `engine:cube` unless it sets `model`. The engine has three:
+
+| Model          | Texture variables                                  | Shape                                         |
+| -------------- | -------------------------------------------------- | --------------------------------------------- |
+| `engine:cube`  | one texture, `{ top, bottom, side }` or `{ front, side }` | A full block.                          |
+| `engine:cross` | `cross`                                            | Two crossed planes, like flowers and saplings. |
+| `engine:crop`  | `crop`                                             | Four planes in a # shape, like wheat.         |
+
+Blocks that aren't full cubes should use the `cutout` (or `translucent`) render layer, because `solid` blocks hide their
+neighbors' faces. This is what minecraft's `"render_type": "minecraft:cutout"` does. They usually want
+`"collision": false` too, and show as a flat sprite of their first texture in inventories.
+
+`blocks/wheat.json` picks a texture per growth stage with `variants`. The keys are conditions on the block's states,
+`"age=3"` or `"age=3,facing=1"` (all have to match), and the first variant that matches replaces the block's `model`,
+`textures` or turns it by `y` (0, 90, 180 or 270 degrees, clockwise seen from above):
+
+```json
+{
+	"format_version": 1,
+	"block": {
+		"id": "bworld:wheat",
+		"model": "engine:crop",
+		"textures": { "crop": "bworld:wheat_stage_0" },
+		"variants": {
+			"age=0": { "textures": { "crop": "bworld:wheat_stage_0" } },
+			"age=1": { "textures": { "crop": "bworld:wheat_stage_1" } }
+		},
+		"render_layer": "cutout",
+		"collision": false,
+		"states": [{ "name": "age", "bits": 3, "default": 0 }]
+	}
+}
+```
+
+Mods add their own models in `models/`, in minecraft's block model format: boxes in pixels (0-16 is the block) with a
+texture per face. `models/slab.json`:
+
+```json
+{
+	"format_version": 1,
+	"model": {
+		"id": "copper_tools:slab",
+		"textures": { "top": "#side", "bottom": "#side" },
+		"elements": [{
+			"from": [0, 0, 0],
+			"to": [16, 8, 16],
+			"faces": {
+				"top": { "texture": "#top" },
+				"bottom": { "texture": "#bottom", "cullface": "bottom" },
+				"north": { "texture": "#side", "cullface": "north" },
+				"south": { "texture": "#side", "cullface": "south" },
+				"west": { "texture": "#side", "cullface": "west" },
+				"east": { "texture": "#side", "cullface": "east" }
+			}
+		}]
+	}
+}
+```
+
+| Field                        | Meaning                                                                                        |
+| ---------------------------- | ---------------------------------------------------------------------------------------------- |
+| `id`                         | The model's id, in the mod's namespace.                                                        |
+| `textures`                   | Defaults for texture variables. Values are texture ids or other variables (`"#side"`).         |
+| `elements[].from`, `to`      | Opposite corners of the box, `[x, y, z]` in pixels.                                            |
+| `elements[].rotation`        | `{ origin, axis, angle, rescale }`: turns the box around `origin` on `x`, `y` or `z` by -45, -22.5, 0, 22.5 or 45 degrees. `rescale` stretches it back to the block's width. |
+| `elements[].shade`           | Darker faces on the sides and bottom, `true` by default. Plants turn it off.                  |
+| `elements[].faces`           | `top`, `bottom`, `north`, `south`, `west` and `east`. Faces are only drawn from the front, so a flat plane needs one face each way. |
+| `faces.*.texture`            | A variable (`"#side"`, filled in by the block's `textures`) or a texture id.                  |
+| `faces.*.uv`                 | `[u1, v1, u2, v2]`, the part of the texture in pixels. Defaults to the part the face covers.  |
+| `faces.*.cullface`           | Hidden when the neighbor on that side is a solid block. Only for faces on the block's edge.   |
+
+Faces flat against the block's edge get smooth lighting and ambient occlusion like a full block's. Anything inside the
+block is lit evenly with the block's own light.
 
 ## Items
 

build.ts

@@ -190,6 +190,7 @@ async function build_mods(mods: LoadedMod[], atlas: AtlasListing) {
 
 		const data: ModData = {
 			blocks: mod.blocks.map((b) => b.json),
+			models: mod.models.map((m) => m.json),
 			items: mod.items.map((i) => i.json),
 			recipes: mod.recipes.map((r) => r.json),
 			ores: mod.ores.map((o) => o.json),

client/level/client_level.ts

@@ -17,6 +17,7 @@ import { create_index_buffer, create_vertex_buffer, destroy_buffer, Texture } fr
 import { crosses_planes } from "../workers/translucent_sort.ts";
 import { Camera } from "../camera.ts";
 import type { Entity } from "../entity/entity.ts";
+import type { ModelJson } from "$/common/block_models.ts";
 
 export interface Block {
 	id: string;
@@ -111,6 +112,7 @@ export class ClientLevel {
 			type: "init",
 			blocks_registry: strip_functions(blocks_registry),
 			block_ids,
+			models: Object.fromEntries(EverythingRegistry.entries<ModelJson>("models")),
 			textures_info: AssetManager.instance.get("bworld:textures_info"),
 			image: { width: this.image.width, height: this.image.height },
 			worldgen_scripts: worldgen_mods.scripts,

client/rendering/item_renderer.ts

@@ -4,6 +4,7 @@ import { AssetManager } from "$/client/assets.ts";
 import { get_sprite_region } from "$/client/sprites.ts";
 import type { ItemEntity } from "$/client/entity/item_entity.ts";
 import { push_vertex, Texture } from "$/client/renderer/mod.ts";
+import { block_item_texture, cube_face_texture } from "$/common/block_models.ts";
 
 // how big items on the ground are drawn, minecraft's ground transform
 const BLOCK_SCALE = 0.25;
@@ -40,9 +41,11 @@ function copies(amount: number) {
 export function render_item_entity(entity: ItemEntity, partial_tick: number) {
 	const atlas = AssetManager.instance.get<Texture>("bworld:textures");
 	const item_info = EverythingRegistry.get<ItemRegistry>("items", entity.item.type_id);
-	const block_info = item_info?.block_id
+	// blocks that aren't cubes, like plants, are drawn as their item's sprite
+	let block_info = item_info?.block_id
 		? EverythingRegistry.get<BlockRegistry>("blocks", item_info.block_id)
 		: undefined;
+	if (block_info && block_item_texture(block_info) !== undefined) block_info = undefined;
 
 	// spinning and bobbing, like minecraft's ItemEntityRenderer
 	const time = entity.age + partial_tick;
@@ -79,7 +82,7 @@ function push_block(
 	};
 
 	for (const face of CUBE_FACES) {
-		const region = get_sprite_region(block_face_texture(block, face.texture));
+		const region = get_sprite_region(cube_face_texture(block, face.texture));
 		push_textured_quad(atlas, region, face.corners.map(([cx, cy, cz]) => corner(cx, cy, cz)), face.shade);
 	}
 }
@@ -121,17 +124,6 @@ function push_textured_quad(atlas: Texture, region: { x: number; y: number }, co
 	}
 }
 
-function block_face_texture(block: BlockRegistry, face: "top" | "bottom" | "front" | "side") {
-	const textures = block.textures;
-	if (typeof textures === "string") {
-		return textures;
-	}
-	if ("top" in textures) {
-		return face === "top" ? textures.top : face === "bottom" ? textures.bottom : textures.side;
-	}
-	return face === "front" ? textures.front : textures.side;
-}
-
 function item_texture(entity: ItemEntity, item_info: ItemRegistry | undefined) {
 	const texture_id = item_info?.texture_id;
 	if (typeof texture_id === "function") {

client/rendering/render_utils.ts

@@ -3,6 +3,7 @@ import { get_sprite_region } from "$/client/sprites.ts";
 import { BlockRegistry, EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";
 import { AssetManager } from "$/client/assets.ts";
 import { ItemStack } from "$/common/inventory.ts";
+import { block_item_texture, cube_face_texture } from "$/common/block_models.ts";
 import { draw_text, draw_texture_region, draw_texture_region_skewed, Texture } from "$/client/renderer/mod.ts";
 
 export function draw_nine_slice(
@@ -206,8 +207,12 @@ export function draw_item(item: ItemStack, x: number, y: number) {
 		throw Error(`Didn't find item registry for '${item.type_id}'`);
 	}
 
-	if (item_info?.block_id) {
-		draw_item_block(item, item_info, x, y);
+	const block_info = item_info.block_id
+		? EverythingRegistry.get<BlockRegistry>("blocks", item_info.block_id)
+		: undefined;
+	// blocks that aren't cubes, like plants, show a flat sprite
+	if (block_info && block_item_texture(block_info) === undefined) {
+		draw_item_block(block_info, x, y);
 	} else {
 		draw_item_item(item, item_info, x, y);
 	}
@@ -251,30 +256,10 @@ function draw_item_item(item: ItemStack, item_info: ItemRegistry, x: number, y:
 	);
 }
 
-function draw_item_block(_item: ItemStack, item_info: ItemRegistry, x: number, y: number) {
-	const block_info = EverythingRegistry.get<BlockRegistry>("blocks", item_info.block_id!);
-
-	if (!block_info) throw new Error(`no textures for ${item_info.block_id}`);
-
-	let front_texture = "engine:missing";
-	let top_texture = "engine:missing";
-	let left_texture = "engine:missing";
-
-	const textures = block_info.textures;
-
-	if (typeof textures === "string") {
-		front_texture = textures;
-		top_texture = textures;
-		left_texture = textures;
-	} else if ("top" in textures && "bottom" in textures && "side" in textures) {
-		top_texture = textures.top;
-		front_texture = textures.side;
-		left_texture = textures.side;
-	} else if ("front" in textures && "side" in textures) {
-		top_texture = textures.side;
-		front_texture = textures.front;
-		left_texture = textures.side;
-	}
+function draw_item_block(block_info: BlockRegistry, x: number, y: number) {
+	const top_texture = cube_face_texture(block_info, "top");
+	const front_texture = cube_face_texture(block_info, "front");
+	const left_texture = cube_face_texture(block_info, "side");
 
 	const atlas = AssetManager.instance.get<Texture>("bworld:textures");
 

client/workers/chunk_messages.ts

@@ -1,6 +1,7 @@
 import type { BlockRegistry } from "$/common/everything_registry.ts";
 import type { SpriteRegion } from "$/common/constants.ts";
 import type { OreJson } from "$/common/mod_data.ts";
+import type { ModelJson } from "$/common/block_models.ts";
 import type { SortType } from "./translucent_sort.ts";
 
 // messages between the main thread and the chunk workers
@@ -14,6 +15,8 @@ export type ToChunkWorker =
 		// the blocks registry without its functions, indexed by numeric id
 		blocks_registry: BlockRegistry[];
 		block_ids: Record<string, number>;
+		// mods' block models by id, the engine's are built in
+		models: Record<string, ModelJson>;
 		textures_info: Record<string, SpriteRegion>;
 		image: { width: number; height: number };
 		// mods' worldgen scripts and ores, so generation matches the server

client/workers/chunk_worker.ts

@@ -6,12 +6,21 @@ import {
 	type BlockRegistry,
 	type RenderLayer,
 } from "$/common/everything_registry.ts";
-import { AIR, CHUNK_HEIGHT, CHUNK_SIZE, ID_MASK, type SpriteRegion, TEXTURE_SIZE } from "$/common/constants.ts";
+import {
+	AIR,
+	CHUNK_AREA,
+	CHUNK_HEIGHT,
+	CHUNK_SIZE,
+	ID_MASK,
+	type SpriteRegion,
+	TEXTURE_SIZE,
+} from "$/common/constants.ts";
 import type { Texture } from "../renderer/types.ts";
 import { type FromChunkWorker, TERRAIN_VERTEX_FLOATS, type ToChunkWorker } from "./chunk_messages.ts";
 import { generate_raw_chunk, WorldgenSetup } from "$/common/generation.ts";
 import { load_worldgen } from "$/common/worldgen_loader.ts";
-import { default_block_value } from "$/common/utils.ts";
+import { default_block_value, get_state_value } from "$/common/utils.ts";
+import { bake_model, block_variant, FACE_CORNERS, find_model, type ModelJson } from "$/common/block_models.ts";
 import {
 	choose_sort_type,
 	FACE_NORMALS,
@@ -37,19 +46,7 @@ const FLOATS_PER_QUAD = 4 * TERRAIN_VERTEX_FLOATS;
 // keeps texture lookups off the sprite's edge
 const UV_PAD = 0.5;
 
-// same order as FACE_NORMALS in translucent_sort.ts
-const FACES = ["top", "bottom", "front", "back", "left", "right"] as const;
-// each face's corners in drawing order (counter clockwise from outside), as offsets from the block's corner
-const FACE_CORNERS = [
-	[[0, 1, 1], [1, 1, 1], [1, 1, 0], [0, 1, 0]],
-	[[0, 0, 0], [1, 0, 0], [1, 0, 1], [0, 0, 1]],
-	[[0, 0, 1], [1, 0, 1], [1, 1, 1], [0, 1, 1]],
-	[[1, 0, 0], [0, 0, 0], [0, 1, 0], [1, 1, 0]],
-	[[0, 0, 0], [0, 0, 1], [0, 1, 1], [0, 1, 0]],
-	[[1, 0, 1], [1, 0, 0], [1, 1, 0], [1, 1, 1]],
-] as const;
-// which end of the sprite each corner gets, u then v (0 = start, 1 = end)
-const CORNER_UVS = [[0, 1], [1, 1], [1, 0], [0, 0]] as const;
+// same order as FACE_NORMALS in translucent_sort.ts, and FACE_CORNERS and CORNER_UVS in block_models.ts
 // minecraft's shading by direction, so faces stay apart even in flat light
 const FACE_SHADE = [1.0, 0.5, 0.8, 0.8, 0.6, 0.6];
 
@@ -86,6 +83,24 @@ const block_lets_light_by = new Uint8Array(TABLE_SIZE);
 const light_tables: LightTables = { opacity: new Uint8Array(TABLE_SIZE), emission: new Uint8Array(TABLE_SIZE) };
 const region = new LightRegion();
 
+// a model's quad ready for the mesher: uvs in the atlas, and for each corner how much of each of the face's
+// four corner lights it gets, so faces smaller than the block are lit like minecraft's
+interface MeshQuad {
+	positions: number[];
+	uvs: number[];
+	face: number;
+	cull: number;
+	flush: boolean;
+	shade: number;
+	sprite: SpriteRegion;
+	// 4 weights per corner
+	light_weights: number[];
+}
+
+let models: Record<string, ModelJson> = {};
+// by block value, or by numeric id for blocks without variants
+const baked = new Map<number, MeshQuad[]>();
+
 let textures_info: TexturesInfo = {};
 let image: Texture;
 let worldgen: WorldgenSetup | undefined;
@@ -100,6 +115,8 @@ self.onmessage = async (event: MessageEvent<ToChunkWorker>) => {
 		case "init":
 			blocks_registry = message.blocks_registry;
 			block_ids = message.block_ids;
+			models = message.models;
+			baked.clear();
 			build_block_tables();
 			textures_info = message.textures_info;
 			image = message.image as Texture;
@@ -115,7 +132,12 @@ self.onmessage = async (event: MessageEvent<ToChunkWorker>) => {
 		case "mesh": {
 			region.fill(message.chunks);
 			region.compute(light_tables);
-			const { solid, cutout, translucent } = make_chunk_mesh(message.chunk_x, message.chunk_z, message.camera);
+			const { solid, cutout, translucent } = make_chunk_mesh(
+				message.chunk_x,
+				message.chunk_z,
+				message.chunks[4]!,
+				message.camera,
+			);
 			post(
 				{
 					type: "meshed",
@@ -263,34 +285,19 @@ function should_flip() {
 	return light(0) + light(2) > light(1) + light(3);
 }
 
-function push_quad(
-	vertices: Float32Array,
-	i: number,
-	face: number,
-	x: number,
-	y: number,
-	z: number,
-	sprite: SpriteRegion,
-	alpha: number,
-) {
-	const u0 = (sprite.x * TEXTURE_SIZE + UV_PAD) / image.width;
-	const v0 = (sprite.y * TEXTURE_SIZE + UV_PAD) / image.height;
-	const u1 = ((sprite.x + 1) * TEXTURE_SIZE - UV_PAD) / image.width;
-	const v1 = ((sprite.y + 1) * TEXTURE_SIZE - UV_PAD) / image.height;
-	const shade = FACE_SHADE[face];
+function push_quad(vertices: Float32Array, i: number, quad: MeshQuad, x: number, y: number, z: number, alpha: number) {
+	const sprite = quad.sprite;
 	// starting from the second corner moves the diagonal, the winding stays the same
 	const first = should_flip() ? 1 : 0;
 
 	for (let k = 0; k < 4; k++) {
 		const corner = (first + k) & 3;
-		const [cx, cy, cz] = FACE_CORNERS[face][corner];
-		const [cu, cv] = CORNER_UVS[corner];
-		const brightness = shade * corner_ao[corner];
-		vertices[i++] = x + cx;
-		vertices[i++] = y + cy;
-		vertices[i++] = z + cz;
-		vertices[i++] = cu ? u1 : u0;
-		vertices[i++] = cv ? v1 : v0;
+		const brightness = quad.shade * corner_ao[corner];
+		vertices[i++] = x + quad.positions[corner * 3];
+		vertices[i++] = y + quad.positions[corner * 3 + 1];
+		vertices[i++] = z + quad.positions[corner * 3 + 2];
+		vertices[i++] = atlas_u(sprite, quad.uvs[corner * 2]);
+		vertices[i++] = atlas_v(sprite, quad.uvs[corner * 2 + 1]);
 		vertices[i++] = brightness;
 		vertices[i++] = brightness;
 		vertices[i++] = brightness;
@@ -302,14 +309,111 @@ function push_quad(
 	return i;
 }
 
+// pixels of a sprite to atlas coordinates, kept off the sprite's edge
+function atlas_u(sprite: SpriteRegion, u: number) {
+	return (sprite.x * TEXTURE_SIZE + Math.min(Math.max(u, UV_PAD), TEXTURE_SIZE - UV_PAD)) / image.width;
+}
+
+function atlas_v(sprite: SpriteRegion, v: number) {
+	return (sprite.y * TEXTURE_SIZE + Math.min(Math.max(v, UV_PAD), TEXTURE_SIZE - UV_PAD)) / image.height;
+}
+
+// the model quads for a block value, baked the first time it's seen
+function block_quads(value: number): MeshQuad[] {
+	const nid = value & ID_MASK;
+	const block = blocks_registry[nid];
+	const key = block.variants ? value : nid;
+	let quads = baked.get(key);
+	if (quads) return quads;
+
+	let states: Record<string, number> | undefined;
+	if (block.variants && block.states) {
+		states = {};
+		for (const state of block.states) states[state.name] = get_state_value(value, block, state.name)!;
+	}
+	const variant = block_variant(block, states);
+	const model = find_model(variant.model, models) ?? find_model("engine:cube", models)!;
+
+	quads = bake_model(model, variant.textures, variant.y).map((quad) => ({
+		positions: quad.positions,
+		uvs: quad.uvs,
+		face: quad.face,
+		cull: quad.cull,
+		flush: quad.flush,
+		shade: quad.shade ? FACE_SHADE[quad.face] : 1,
+		sprite: textures_info[quad.texture] ?? textures_info["engine:missing"],
+		light_weights: light_weights(quad.face, quad.positions),
+	}));
+	baked.set(key, quads);
+	return quads;
+}
+
+// bilinear weights of the face's four corners at each of the quad's corners
+function light_weights(face: number, positions: number[]) {
+	const axes = [0, 1, 2].filter((axis) => FACE_NORMALS[face][axis] === 0);
+	const weights: number[] = [];
+	for (let k = 0; k < 4; k++) {
+		for (const corner of FACE_CORNERS[face]) {
+			let weight = 1;
+			for (const axis of axes) {
+				const t = Math.min(Math.max(positions[k * 3 + axis], 0), 1);
+				weight *= corner[axis] ? t : 1 - t;
+			}
+			weights.push(weight);
+		}
+	}
+	return weights;
+}
+
+// light for a quad smaller than a face, or not on the block's edge at all
+const face_sky = new Float32Array(4);
+const face_block = new Float32Array(4);
+const face_ao = new Float32Array(4);
+
+function light_quad(quad: MeshQuad, index: number, y: number, face_offsets: number[]) {
+	if (quad.flush) {
+		light_face_corners(quad.face, index + face_offsets[quad.face], y + FACE_NORMALS[quad.face][1]);
+		face_sky.set(corner_sky);
+		face_block.set(corner_block);
+		face_ao.set(corner_ao);
+		const w = quad.light_weights;
+		for (let k = 0; k < 4; k++) {
+			let sky = 0;
+			let block = 0;
+			let ao = 0;
+			for (let c = 0; c < 4; c++) {
+				sky += w[k * 4 + c] * face_sky[c];
+				block += w[k * 4 + c] * face_block[c];
+				ao += w[k * 4 + c] * face_ao[c];
+			}
+			corner_sky[k] = sky;
+			corner_block[k] = block;
+			corner_ao[k] = ao;
+		}
+		return;
+	}
+
+	// inside the block: its own cell's light, or the cell it faces if the block stops light itself
+	let cell = index;
+	let cell_y = y;
+	if (light_tables.opacity[region_block(region, index, y)] === 15) {
+		cell = index + face_offsets[quad.face];
+		cell_y = y + FACE_NORMALS[quad.face][1];
+	}
+	corner_sky.fill(region_sky(region, cell, cell_y));
+	corner_block.fill(region_block_light(region, cell, cell_y));
+	corner_ao.fill(1);
+}
+
 // region has to be filled and lit first
-function make_chunk_mesh(chunk_x: number, chunk_z: number, camera: number[]) {
+// values is the middle chunk's blocks with their states, for models that change with them
+function make_chunk_mesh(chunk_x: number, chunk_z: number, values: Uint32Array, camera: number[]) {
 	const layers = [SOLID, CUTOUT, TRANSLUCENT].map(() => ({ vertices: new Float32Array(4096), floats: 0 }));
 	// for sorting the translucent quads
 	let centers = new Float32Array(256);
 	let faces = new Uint8Array(256);
 
-	// where the neighbor on each face is, same order as FACES
+	// where the neighbor on each face is, same order as FACE_NORMALS
 	const face_offsets = FACE_NORMALS.map(([nx, ny, nz]) => nx + ny * REGION_LAYER + nz * REGION_SIZE);
 
 	for (let y = 0; y < CHUNK_HEIGHT; y++) {
@@ -325,73 +429,33 @@ function make_chunk_mesh(chunk_x: number, chunk_z: number, camera: number[]) {
 				const layer = layers[layer_id];
 				const alpha = layer_id === TRANSLUCENT ? block_info.alpha ?? 1 : 1;
 
-				const texture_ids = {
-					top: "engine:missing",
-					bottom: "engine:missing",
-					front: "engine:missing",
-					back: "engine:missing",
-					left: "engine:missing",
-					right: "engine:missing",
-				};
-
-				const textures = block_info.textures;
-				if (!textures) throw new Error(`no textures for ${block_nid}`);
-
-				if (typeof textures === "string") {
-					texture_ids.top = textures;
-					texture_ids.bottom = textures;
-					texture_ids.front = textures;
-					texture_ids.back = textures;
-					texture_ids.left = textures;
-					texture_ids.right = textures;
-				} else if ("top" in textures && "bottom" in textures && "side" in textures) {
-					texture_ids.top = textures.top;
-					texture_ids.bottom = textures.bottom;
-					texture_ids.front = textures.side;
-					texture_ids.back = textures.side;
-					texture_ids.left = textures.side;
-					texture_ids.right = textures.side;
-				} else if ("front" in textures && "side" in textures) {
-					texture_ids.top = textures.side;
-					texture_ids.bottom = textures.side;
-					texture_ids.front = textures.front;
-					texture_ids.back = textures.side;
-					texture_ids.left = textures.side;
-					texture_ids.right = textures.side;
-				}
-
 				const wx = chunk_x * CHUNK_SIZE + x;
 				const wz = chunk_z * CHUNK_SIZE + z;
 
-				for (let face = 0; face < 6; face++) {
-					const front = index + face_offsets[face];
-					const front_y = y + FACE_NORMALS[face][1];
-					if (!show_face(block_nid, region_block(region, front, front_y))) {
-						continue;
+				for (const quad of block_quads(values[y * CHUNK_AREA + z * CHUNK_SIZE + x])) {
+					if (quad.cull >= 0) {
+						const neighbor = region_block(
+							region,
+							index + face_offsets[quad.cull],
+							y + FACE_NORMALS[quad.cull][1],
+						);
+						if (!show_face(block_nid, neighbor)) continue;
 					}
 
-					light_face_corners(face, front, front_y);
+					light_quad(quad, index, y, face_offsets);
 					layer.vertices = ensure_capacity(layer.vertices, layer.floats + FLOATS_PER_QUAD);
-					layer.floats = push_quad(
-						layer.vertices,
-						layer.floats,
-						face,
-						wx,
-						y,
-						wz,
-						textures_info[texture_ids[FACES[face]]],
-						alpha,
-					);
+					layer.floats = push_quad(layer.vertices, layer.floats, quad, wx, y, wz, alpha);
 
 					if (layer_id === TRANSLUCENT) {
-						const quad = layer.floats / FLOATS_PER_QUAD - 1;
-						centers = ensure_capacity(centers, (quad + 1) * 3);
-						faces = ensure_capacity(faces, quad + 1);
-						const [nx, ny, nz] = FACE_NORMALS[face];
-						centers[quad * 3] = wx + 0.5 + nx * 0.5;
-						centers[quad * 3 + 1] = y + 0.5 + ny * 0.5;
-						centers[quad * 3 + 2] = wz + 0.5 + nz * 0.5;
-						faces[quad] = face;
+						// sorting treats every quad as facing along an axis, rotated ones too
+						const q = layer.floats / FLOATS_PER_QUAD - 1;
+						centers = ensure_capacity(centers, (q + 1) * 3);
+						faces = ensure_capacity(faces, q + 1);
+						const p = quad.positions;
+						centers[q * 3] = wx + (p[0] + p[6]) / 2;
+						centers[q * 3 + 1] = y + (p[1] + p[7]) / 2;
+						centers[q * 3 + 2] = wz + (p[2] + p[8]) / 2;
+						faces[q] = quad.face;
 					}
 				}
 			}

common/block_models.ts

@@ -0,0 +1,308 @@
+// block models, in the shape of minecraft's block model json: boxes ("elements") with a texture per face.
+// a block picks one with "model" and fills in its texture variables with "textures". baking turns a model
+// into quads in block space (0 to 1) that the chunk mesher and the item renderers draw
+import type { BlockRegistry, BlockTextures } from "./everything_registry.ts";
+
+export type ModelFace = "top" | "bottom" | "north" | "south" | "west" | "east";
+export const MODEL_FACES: ModelFace[] = ["top", "bottom", "north", "south", "west", "east"];
+
+export interface ModelFaceJson {
+	// a texture variable like "#side", or a texture id
+	texture: string;
+	// the part of the texture, [u1, v1, u2, v2] in pixels (0-16). defaults to the part the face covers
+	uv?: [number, number, number, number];
+	// hidden when the neighbor on this side hides faces (a solid block)
+	cullface?: ModelFace;
+}
+
+export interface ModelElementJson {
+	// corners of the box in pixels, 0-16 is the block
+	from: [number, number, number];
+	to: [number, number, number];
+	rotation?: {
+		origin: [number, number, number];
+		axis: "x" | "y" | "z";
+		// -45, -22.5, 0, 22.5 or 45
+		angle: number;
+		// stretch the rotated faces back to the block's size, like the cross model does
+		rescale?: boolean;
+	};
+	// directional shading, off for plants so they look the same from every side
+	shade?: boolean;
+	faces: Partial<Record<ModelFace, ModelFaceJson>>;
+}
+
+export interface ModelJson {
+	id: string;
+	// defaults for texture variables, can point at other variables ("top": "#side")
+	textures?: Record<string, string>;
+	elements: ModelElementJson[];
+}
+
+// a model a block uses, and the textures it fills in
+export interface BlockVariant {
+	model?: string;
+	textures?: BlockTextures;
+	// turns the model around the vertical axis, clockwise seen from above: 0, 90, 180 or 270
+	y?: number;
+}
+
+export const DEFAULT_MODEL = "engine:cube";
+
+const cube_face = (texture: string, cullface: ModelFace): ModelFaceJson => ({ texture, cullface });
+
+// the engine's own models
+export const BUILTIN_MODELS: Record<string, ModelJson> = {
+	// a full block. "textures" can be one texture, { top, bottom, side } or { front, side }
+	"engine:cube": {
+		id: "engine:cube",
+		textures: { top: "#side", bottom: "#side", front: "#side" },
+		elements: [{
+			from: [0, 0, 0],
+			to: [16, 16, 16],
+			faces: {
+				top: cube_face("#top", "top"),
+				bottom: cube_face("#bottom", "bottom"),
+				north: cube_face("#side", "north"),
+				south: cube_face("#front", "south"),
+				west: cube_face("#side", "west"),
+				east: cube_face("#side", "east"),
+			},
+		}],
+	},
+	// two crossed planes, like flowers and saplings. uses the "cross" texture
+	"engine:cross": {
+		id: "engine:cross",
+		elements: [
+			cross_plane(45),
+			cross_plane(-45),
+		],
+	},
+	// four planes in a # shape, like wheat. uses the "crop" texture
+	"engine:crop": {
+		id: "engine:crop",
+		elements: [
+			{ from: [4, 0, 0], to: [4, 16, 16], shade: false, faces: both_ways("west", "east", "#crop") },
+			{ from: [12, 0, 0], to: [12, 16, 16], shade: false, faces: both_ways("west", "east", "#crop") },
+			{ from: [0, 0, 4], to: [16, 16, 4], shade: false, faces: both_ways("north", "south", "#crop") },
+			{ from: [0, 0, 12], to: [16, 16, 12], shade: false, faces: both_ways("north", "south", "#crop") },
+		],
+	},
+};
+
+function cross_plane(angle: number): ModelElementJson {
+	return {
+		from: [0.8, 0, 8],
+		to: [15.2, 16, 8],
+		rotation: { origin: [8, 8, 8], axis: "y", angle, rescale: true },
+		shade: false,
+		faces: both_ways("north", "south", "#cross"),
+	};
+}
+
+// a flat element seen from both sides, since faces are only drawn from the front
+function both_ways(a: ModelFace, b: ModelFace, texture: string) {
+	return { [a]: { texture, uv: [0, 0, 16, 16] }, [b]: { texture, uv: [0, 0, 16, 16] } } as Partial<
+		Record<ModelFace, ModelFaceJson>
+	>;
+}
+
+export function find_model(id: string, models: Record<string, ModelJson>): ModelJson | undefined {
+	return BUILTIN_MODELS[id] ?? models[id];
+}
+
+// what a texture reference means for a block: "#name" looks up the block's textures, then the model's
+// defaults, and anything else is already a texture id
+export function resolve_texture(reference: string, textures: BlockTextures | undefined, model?: ModelJson): string {
+	for (let depth = 0; depth < 8 && reference.startsWith("#"); depth++) {
+		const name = reference.slice(1);
+		if (typeof textures === "string") return textures;
+		const next = (textures as Record<string, string> | undefined)?.[name] ?? model?.textures?.[name];
+		if (next === undefined) return "engine:missing";
+		reference = next;
+	}
+	return reference.startsWith("#") ? "engine:missing" : reference;
+}
+
+// the block's model and textures for a value with state bits, from the first variant whose conditions match
+export function block_variant(block: BlockRegistry, states?: Record<string, number>): Required<BlockVariant> {
+	const variant: Required<BlockVariant> = {
+		model: block.model ?? DEFAULT_MODEL,
+		textures: block.textures,
+		y: 0,
+	};
+	if (!block.variants || !states) return variant;
+	for (const [condition, override] of Object.entries(block.variants)) {
+		if (variant_matches(condition, states)) {
+			return {
+				model: override.model ?? variant.model,
+				textures: override.textures ?? variant.textures,
+				y: override.y ?? 0,
+			};
+		}
+	}
+	return variant;
+}
+
+// "age=7" or "age=7,facing=2", "" matches everything
+export function variant_matches(condition: string, states: Record<string, number>) {
+	if (condition === "") return true;
+	return condition.split(",").every((part) => {
+		const [name, value] = part.split("=");
+		return states[name.trim()] === Number(value);
+	});
+}
+
+// for inventories and dropped items: blocks with a full cube draw as a cube, anything else as a flat sprite
+// of its first texture, like minecraft's items for plants
+export function block_item_texture(block: BlockRegistry): string | undefined {
+	if ((block.model ?? DEFAULT_MODEL) === DEFAULT_MODEL) return undefined;
+	const textures = block.textures;
+	if (typeof textures === "string") return textures;
+	return Object.values(textures)[0] ?? "engine:missing";
+}
+
+export function cube_face_texture(block: BlockRegistry, face: "top" | "bottom" | "front" | "side") {
+	return resolve_texture(`#${face}`, block.textures, BUILTIN_MODELS[DEFAULT_MODEL]);
+}
+
+// baking
+
+export interface BakedQuad {
+	// 4 corners counter clockwise seen from the front, x y z in block space
+	positions: number[];
+	// u v per corner, in pixels of the texture (0-16)
+	uvs: number[];
+	texture: string;
+	// the side it faces most, as the mesher's face index (see FACE_INDEX)
+	face: number;
+	// the side whose neighbor can hide it, or -1
+	cull: number;
+	// on the block's edge facing straight out, so it's lit like a full block's face
+	flush: boolean;
+	shade: boolean;
+}
+
+// the mesher's face order: top, bottom, front (+z), back (-z), left (-x), right (+x)
+export const FACE_INDEX: Record<ModelFace, number> = { top: 0, bottom: 1, south: 2, north: 3, west: 4, east: 5 };
+const FACE_NORMALS = [[0, 1, 0], [0, -1, 0], [0, 0, 1], [0, 0, -1], [-1, 0, 0], [1, 0, 0]];
+// each face's corners in drawing order as which end of the box they're at, same as the mesher
+export const FACE_CORNERS = [
+	[[0, 1, 1], [1, 1, 1], [1, 1, 0], [0, 1, 0]],
+	[[0, 0, 0], [1, 0, 0], [1, 0, 1], [0, 0, 1]],
+	[[0, 0, 1], [1, 0, 1], [1, 1, 1], [0, 1, 1]],
+	[[1, 0, 0], [0, 0, 0], [0, 1, 0], [1, 1, 0]],
+	[[0, 0, 0], [0, 0, 1], [0, 1, 1], [0, 1, 0]],
+	[[1, 0, 1], [1, 0, 0], [1, 1, 0], [1, 1, 1]],
+] as const;
+// which end of the uv rectangle each corner gets, u then v
+export const CORNER_UVS = [[0, 1], [1, 1], [1, 0], [0, 0]] as const;
+// the face a face becomes after turning the model 90 degrees clockwise seen from above
+const TURN_Y = [0, 1, 4, 5, 3, 2];
+
+// minecraft's default uvs: the part of the texture the face would cover if the texture was wrapped around the block
+function default_uv(face: ModelFace, from: number[], to: number[]): [number, number, number, number] {
+	switch (face) {
+		case "top":
+			return [from[0], from[2], to[0], to[2]];
+		case "bottom":
+			return [from[0], 16 - to[2], to[0], 16 - from[2]];
+		case "north":
+			return [16 - to[0], 16 - to[1], 16 - from[0], 16 - from[1]];
+		case "south":
+			return [from[0], 16 - to[1], to[0], 16 - from[1]];
+		case "west":
+			return [from[2], 16 - to[1], to[2], 16 - from[1]];
+		case "east":
+			return [16 - to[2], 16 - to[1], 16 - from[2], 16 - from[1]];
+	}
+}
+
+const EPSILON = 1e-4;
+
+export function bake_model(model: ModelJson, textures: BlockTextures | undefined, y_rotation = 0): BakedQuad[] {
+	const quads: BakedQuad[] = [];
+	const turns = ((Math.round(y_rotation / 90) % 4) + 4) % 4;
+
+	for (const element of model.elements) {
+		const rotate = element_rotation(element);
+		for (const face of MODEL_FACES) {
+			const face_json = element.faces[face];
+			if (!face_json) continue;
+			const index = FACE_INDEX[face];
+			const uv = face_json.uv ?? default_uv(face, element.from, element.to);
+
+			const positions: number[] = [];
+			const uvs: number[] = [];
+			FACE_CORNERS[index].forEach((corner, k) => {
+				let point = corner.map((end, axis) => (end ? element.to[axis] : element.from[axis]) / 16);
+				point = rotate(point);
+				for (let t = 0; t < turns; t++) point = [1 - point[2], point[1], point[0]];
+				positions.push(...point);
+				const [cu, cv] = CORNER_UVS[k];
+				uvs.push(cu ? uv[2] : uv[0], cv ? uv[3] : uv[1]);
+			});
+
+			let cull = face_json.cullface ? FACE_INDEX[face_json.cullface] : -1;
+			for (let t = 0; t < turns && cull >= 0; t++) cull = TURN_Y[cull];
+			const { face: facing, flush } = classify(positions);
+			quads.push({
+				positions,
+				uvs,
+				texture: resolve_texture(face_json.texture, textures, model),
+				face: facing,
+				cull,
+				flush,
+				shade: element.shade ?? true,
+			});
+		}
+	}
+	return quads;
+}
+
+// turns a point (in block space) by the element's rotation
+function element_rotation(element: ModelElementJson): (point: number[]) => number[] {
+	const rotation = element.rotation;
+	if (!rotation || rotation.angle === 0) return (point) => point;
+
+	const axis = { x: 0, y: 1, z: 2 }[rotation.axis];
+	// the two axes that move, in the order that makes a positive angle counter clockwise looking down the axis
+	const [a, b] = axis === 0 ? [1, 2] : axis === 1 ? [2, 0] : [0, 1];
+	const radians = rotation.angle * Math.PI / 180;
+	const cos = Math.cos(radians);
+	const sin = Math.sin(radians);
+	// minecraft's rescale keeps a 45 degree face as wide as the block
+	const scale = rotation.rescale ? 1 / Math.max(Math.abs(cos), Math.abs(sin)) : 1;
+	const origin = rotation.origin.map((v) => v / 16);
+
+	return (point) => {
+		const out = [...point];
+		const da = point[a] - origin[a];
+		const db = point[b] - origin[b];
+		out[a] = origin[a] + (da * cos - db * sin) * scale;
+		out[b] = origin[b] + (da * sin + db * cos) * scale;
+		return out;
+	};
+}
+
+// which way a quad faces most, and whether it's flat against the block's edge
+function classify(p: number[]): { face: number; flush: boolean } {
+	const e1 = [p[3] - p[0], p[4] - p[1], p[5] - p[2]];
+	const e2 = [p[9] - p[0], p[10] - p[1], p[11] - p[2]];
+	const normal = [e1[1] * e2[2] - e1[2] * e2[1], e1[2] * e2[0] - e1[0] * e2[2], e1[0] * e2[1] - e1[1] * e2[0]];
+
+	let face = 0;
+	let best = -Infinity;
+	FACE_NORMALS.forEach((n, i) => {
+		const dot = n[0] * normal[0] + n[1] * normal[1] + n[2] * normal[2];
+		if (dot > best) {
+			best = dot;
+			face = i;
+		}
+	});
+
+	const axis = FACE_NORMALS[face].findIndex((v) => v !== 0);
+	const edge = FACE_NORMALS[face][axis] > 0 ? 1 : 0;
+	const flush = [0, 1, 2, 3].every((k) => Math.abs(p[k * 3 + axis] - edge) < EPSILON);
+	return { face, flush };
+}

common/everything_registry.ts

@@ -1,4 +1,5 @@
 import type { ItemStack } from "./inventory.ts";
+import type { BlockVariant } from "./block_models.ts";
 
 export class EverythingRegistry {
 	static #key_to_id = new Map<string, Map<string, number>>();
@@ -65,16 +66,9 @@ export class EverythingRegistry {
 	}
 }
 
-interface TextureSideTopBottom {
-	top: string;
-	bottom: string;
-	side: string;
-}
-
-interface TextureFront {
-	front: string;
-	side: string;
-}
+// one texture for everything, or the model's texture variables: { top, bottom, side } or { front, side } for
+// cubes, { crop } for engine:crop and so on
+export type BlockTextures = string | Record<string, string>;
 
 export interface BlockStateDefinition {
 	name: string;
@@ -88,11 +82,6 @@ interface CompiledStateDefinition {
 	shift: number;
 }
 
-interface BlockStateVariant {
-	model: string;
-	y: number;
-}
-
 // solid: fully opaque. cutout: texels are either opaque or see-through (leaves).
 // translucent: blended and sorted back to front (water, glass)
 export const RENDER_LAYERS = ["solid", "cutout", "translucent"] as const;
@@ -110,7 +99,9 @@ export function block_light_emission(block: BlockRegistry | undefined): number {
 
 export interface BlockRegistry {
 	id: string;
-	textures: string | TextureSideTopBottom | TextureFront;
+	textures: BlockTextures;
+	// the block model, engine:cube when not set. see common/block_models.ts
+	model?: string;
 	// solid when not set. anything else doesn't hide its neighbors' faces
 	render_layer?: RenderLayer;
 	// hide faces between two of this block, like glass and water. defaults to true for translucent blocks
@@ -128,7 +119,8 @@ export interface BlockRegistry {
 	drop_table?: string;
 
 	states?: BlockStateDefinition[];
-	variants?: Record<string, BlockStateVariant>;
+	// a different model or textures for some states, by conditions like "age=7". the first match wins
+	variants?: Record<string, BlockVariant>;
 
 	// right clicking it does something instead of placing a block, clients don't predict placing against it.
 	// behavior runs on the server, see server/game/blocks.ts

common/mod_data.ts

@@ -7,6 +7,7 @@ import {
 	RENDER_LAYERS,
 	type RenderLayer,
 } from "./everything_registry.ts";
+import { type BlockVariant, MODEL_FACES, type ModelFace } from "./block_models.ts";
 
 export const FORMAT_VERSION = 1;
 export const ID_PATTERN = /^[a-z0-9_]+:[a-z0-9_]+$/;
@@ -31,6 +32,8 @@ export interface ManifestJson {
 export interface BlockJson {
 	id: string;
 	textures: BlockTextures;
+	model?: string;
+	variants?: Record<string, BlockVariant>;
 	render_layer?: RenderLayer;
 	cull_same?: boolean;
 	light_emission?: number;
@@ -89,6 +92,8 @@ export interface GridRecipe {
 
 export function block_to_json(block: BlockRegistry, has_item: boolean): BlockJson {
 	const json: BlockJson = { id: block.id, textures: block.textures };
+	if (block.model !== undefined) json.model = block.model;
+	if (block.variants !== undefined) json.variants = block.variants;
 	if (block.render_layer && block.render_layer !== "solid") json.render_layer = block.render_layer;
 	if (block.cull_same !== undefined) json.cull_same = block.cull_same;
 	if (block.light_emission !== undefined) json.light_emission = block.light_emission;
@@ -115,6 +120,8 @@ export function block_from_json(json: BlockJson): { block: BlockRegistry; has_it
 		textures: json.textures,
 		has_collision: json.collision ?? true,
 	};
+	if (json.model !== undefined) block.model = json.model;
+	if (json.variants !== undefined) block.variants = json.variants;
 	const render_layer = json.render_layer ?? (json.transparent ? "translucent" : undefined);
 	if (render_layer && render_layer !== "solid") block.render_layer = render_layer;
 	if (json.cull_same !== undefined) block.cull_same = json.cull_same;
@@ -255,12 +262,45 @@ export function validate_manifest(json: unknown, folder_name: string): Problems
 export function validate_block(json: unknown): Problems {
 	if (!is_object(json)) return ["block must be an object"];
 	const problems = validate_id(json.id, "id");
+	if (json.model !== undefined) problems.push(...validate_id(json.model, "model"));
+	const is_cube = json.model === undefined || json.model === "engine:cube";
 	const textures = json.textures;
+	if (is_cube) {
 		const texture_ok = typeof textures === "string" ||
 			(is_object(textures) &&
 				(["top", "bottom", "side"].every((k) => typeof textures[k] === "string") ||
 					["front", "side"].every((k) => typeof textures[k] === "string")));
 		if (!texture_ok) problems.push("textures must be a texture id, { top, bottom, side } or { front, side }");
+	} else {
+		problems.push(...validate_textures(textures, "textures"));
+	}
+	if (json.variants !== undefined) {
+		if (!is_object(json.variants)) {
+			problems.push('variants must map conditions like "age=3" to { model, textures, y }');
+		} else {
+			const names = new Set(Array.isArray(json.states) ? json.states.map((s) => is_object(s) ? s.name : "") : []);
+			for (const [condition, variant] of Object.entries(json.variants)) {
+				const where = `variants["${condition}"]`;
+				for (const part of condition === "" ? [] : condition.split(",")) {
+					const [name, value] = part.split("=").map((p) => p.trim());
+					if (!names.has(name) || !/^\d+$/.test(value ?? "")) {
+						problems.push(`${where}: "${part}" must be a state of this block and a number, like age=3`);
+					}
+				}
+				if (!is_object(variant)) {
+					problems.push(`${where} must be { model, textures, y }`);
+					continue;
+				}
+				if (variant.model !== undefined) problems.push(...validate_id(variant.model, `${where}.model`));
+				if (variant.textures !== undefined) {
+					problems.push(...validate_textures(variant.textures, `${where}.textures`));
+				}
+				if (variant.y !== undefined && ![0, 90, 180, 270].includes(variant.y as number)) {
+					problems.push(`${where}.y must be 0, 90, 180 or 270`);
+				}
+			}
+		}
+	}
 	if (json.render_layer !== undefined && !RENDER_LAYERS.includes(json.render_layer as RenderLayer)) {
 		problems.push(`render_layer must be one of ${RENDER_LAYERS.join(", ")}`);
 	}
@@ -294,6 +334,72 @@ export function validate_block(json: unknown): Problems {
 	return problems;
 }
 
+export function validate_model(json: unknown): Problems {
+	if (!is_object(json)) return ["model must be an object"];
+	const problems = validate_id(json.id, "id");
+	if (json.textures !== undefined) problems.push(...validate_textures(json.textures, "textures", true));
+	if (!Array.isArray(json.elements) || json.elements.length === 0) {
+		problems.push("elements must be a list of boxes");
+		return problems;
+	}
+	json.elements.forEach((element, i) => {
+		const where = `elements[${i}]`;
+		if (!is_object(element)) {
+			problems.push(`${where} must be { from, to, faces }`);
+			return;
+		}
+		for (const key of ["from", "to"]) {
+			const point = element[key];
+			if (!Array.isArray(point) || point.length !== 3 || !point.every((v) => typeof v === "number")) {
+				problems.push(`${where}.${key} must be [x, y, z] in pixels`);
+			}
+		}
+		const rotation = element.rotation;
+		if (rotation !== undefined) {
+			if (
+				!is_object(rotation) || !["x", "y", "z"].includes(rotation.axis as string) ||
+				![-45, -22.5, 0, 22.5, 45].includes(rotation.angle as number) || !Array.isArray(rotation.origin)
+			) {
+				problems.push(
+					`${where}.rotation must be { origin, axis: x, y or z, angle: -45, -22.5, 0, 22.5 or 45 }`,
+				);
+			}
+		}
+		if (element.shade !== undefined && typeof element.shade !== "boolean") {
+			problems.push(`${where}.shade must be true or false`);
+		}
+		if (!is_object(element.faces)) {
+			problems.push(`${where}.faces must map sides to { texture }`);
+			return;
+		}
+		for (const [side, face] of Object.entries(element.faces)) {
+			if (!MODEL_FACES.includes(side as ModelFace)) {
+				problems.push(`${where}.faces: "${side}" isn't one of ${MODEL_FACES.join(", ")}`);
+			}
+			if (!is_object(face) || typeof face.texture !== "string") {
+				problems.push(`${where}.faces.${side} needs a texture, like "#side"`);
+				continue;
+			}
+			if (face.uv !== undefined && (!Array.isArray(face.uv) || face.uv.length !== 4)) {
+				problems.push(`${where}.faces.${side}.uv must be [u1, v1, u2, v2] in pixels`);
+			}
+			if (face.cullface !== undefined && !MODEL_FACES.includes(face.cullface as ModelFace)) {
+				problems.push(`${where}.faces.${side}.cullface isn't one of ${MODEL_FACES.join(", ")}`);
+			}
+		}
+	});
+	return problems;
+}
+
+// a texture id, or texture variables mapped to ids. a model's own defaults may also point at variables ("#side")
+function validate_textures(value: unknown, field: string, allow_variables = false): Problems {
+	if (typeof value === "string") return validate_id(value, field);
+	if (!is_object(value)) return [`${field} must be a texture id or { variable: texture id }`];
+	return Object.entries(value).flatMap(([name, id]) =>
+		allow_variables && typeof id === "string" && id.startsWith("#") ? [] : validate_id(id, `${field}.${name}`)
+	);
+}
+
 export function validate_item(json: unknown): Problems {
 	if (!is_object(json)) return ["item must be an object"];
 	const problems = validate_id(json.id, "id");

common/mod_loader.ts

@@ -11,10 +11,13 @@ import {
 	RecipeJson,
 } from "./mod_data.ts";
 import { register_block_item } from "./utils.ts";
+import type { ModelJson } from "./block_models.ts";
 
 // everything a mod's json files hold, merged into one file by the build (build/mods/<id>/<hash>/data.json)
 export interface ModData {
 	blocks: BlockJson[];
+	// block models, see common/block_models.ts
+	models?: ModelJson[];
 	items: ItemJson[];
 	recipes: RecipeJson[];
 	ores: OreJson[];
@@ -66,6 +69,9 @@ export function register_mod_data(mods: { id: string; data: ModData }[]): Recipe
 			throw new ModLoadError(id, message);
 		};
 		try {
+			for (const model of data.models ?? []) {
+				EverythingRegistry.register<ModelJson>("models", model.id, model);
+			}
 			for (const json of data.blocks) {
 				const { block, has_item } = block_from_json(json);
 				EverythingRegistry.register<BlockRegistry>("blocks", block.id, block);

common/utils.ts

@@ -1,5 +1,6 @@
 import { ID_MASK, STATE_SHIFT } from "./constants.ts";
 import { BlockRegistry, EverythingRegistry, ItemRegistry } from "./everything_registry.ts";
+import { block_item_texture, cube_face_texture } from "./block_models.ts";
 
 export function point_inside_rec(
 	point_x: number,
@@ -38,11 +39,8 @@ export function distance_point_point(ax: number, ay: number, az: number, bx: num
 }
 
 export function register_block_item(block: BlockRegistry) {
-	// TODO: handle block textures
-	let texture_id = "engine:missing";
-	if (typeof block.textures === "string") {
-		texture_id = block.textures;
-	}
+	// cubes are drawn from the block's textures, anything else as a sprite
+	const texture_id = block_item_texture(block) ?? cube_face_texture(block, "side");
 	EverythingRegistry.register<ItemRegistry>("items", block.id, {
 		texture_id,
 		block_id: block.id,

mods/bworld/blocks/wheat.json

@@ -0,0 +1,66 @@
+{
+	"format_version": 1,
+	"block": {
+		"id": "bworld:wheat",
+		"textures": {
+			"crop": "bworld:wheat_stage_0"
+		},
+		"model": "engine:crop",
+		"variants": {
+			"age=0": {
+				"textures": {
+					"crop": "bworld:wheat_stage_0"
+				}
+			},
+			"age=1": {
+				"textures": {
+					"crop": "bworld:wheat_stage_1"
+				}
+			},
+			"age=2": {
+				"textures": {
+					"crop": "bworld:wheat_stage_2"
+				}
+			},
+			"age=3": {
+				"textures": {
+					"crop": "bworld:wheat_stage_3"
+				}
+			},
+			"age=4": {
+				"textures": {
+					"crop": "bworld:wheat_stage_4"
+				}
+			},
+			"age=5": {
+				"textures": {
+					"crop": "bworld:wheat_stage_5"
+				}
+			},
+			"age=6": {
+				"textures": {
+					"crop": "bworld:wheat_stage_6"
+				}
+			},
+			"age=7": {
+				"textures": {
+					"crop": "bworld:wheat_stage_7"
+				}
+			}
+		},
+		"render_layer": "cutout",
+		"collision": false,
+		"mining": {
+			"toughness": 0
+		},
+		"drops": "bworld:wheat_seeds",
+		"item": false,
+		"states": [
+			{
+				"name": "age",
+				"bits": 3,
+				"default": 0
+			}
+		]
+	}
+}

mods/bworld/items/bone_meal.json

@@ -0,0 +1,7 @@
+{
+	"format_version": 1,
+	"item": {
+		"id": "bworld:bone_meal",
+		"texture": "bworld:bone_meal"
+	}
+}

mods/bworld/items/wheat.json

@@ -0,0 +1,7 @@
+{
+	"format_version": 1,
+	"item": {
+		"id": "bworld:wheat",
+		"texture": "bworld:wheat"
+	}
+}

mods/bworld/items/wheat_seeds.json

@@ -0,0 +1,8 @@
+{
+	"format_version": 1,
+	"item": {
+		"id": "bworld:wheat_seeds",
+		"texture": "bworld:wheat_seeds",
+		"places": "bworld:wheat"
+	}
+}

server/game/blocks.ts

@@ -1,6 +1,7 @@
 import { Container, ItemStack } from "$/common/inventory.ts";
 import { ScreenLayout } from "$/common/protocol.ts";
-import { EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";
+import { BlockRegistry, EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";
+import { get_state_value, set_state_value } from "$/common/utils.ts";
 import type { RecipeBook } from "$/common/mod_loader.ts";
 import type { GameServer } from "./game_server.ts";
 import type { ServerPlayer } from "./player.ts";
@@ -51,6 +52,36 @@ function hoe_into_hoed_dirt(
 BLOCK_BEHAVIORS["bworld:grass"] = { on_interact: hoe_into_hoed_dirt };
 BLOCK_BEHAVIORS["bworld:dirt"] = { on_interact: hoe_into_hoed_dirt };
 
+// crops
+
+// minecraft's bone meal: a crop grows 2 to 5 stages at once, and the bone meal is used up
+function grow_with_bone_meal(
+	game: GameServer,
+	block: { x: number; y: number; z: number; id: string },
+	player: ServerPlayer,
+): boolean {
+	const held = player.held_item;
+	if (held?.type_id !== "bworld:bone_meal") {
+		return false;
+	}
+	const info = EverythingRegistry.get<BlockRegistry>("blocks", block.id)!;
+	const value = game.world.get_block_value(block.x, block.y, block.z);
+	const age = get_state_value(value, info, "age")!;
+	const max_age = 2 ** info.states!.find((s) => s.name === "age")!.bits - 1;
+	// fully grown, keep the bone meal
+	if (age >= max_age) {
+		return false;
+	}
+
+	const new_age = Math.min(age + 1, max_age);
+	game.set_block_state(block.x, block.y, block.z, set_state_value(value, info, "age", new_age)! >>> 16);
+	const slot = player.inventory.get_slot(player.selected_slot);
+	slot.amount = slot.amount! - 1;
+	return true;
+}
+
+BLOCK_BEHAVIORS["bworld:wheat"] = { on_interact: grow_with_bone_meal };
+
 // chest
 
 const CHEST_LAYOUT: ScreenLayout = {

tests/block_models_test.ts

@@ -0,0 +1,74 @@
+import { assert, assertEquals } from "@std/assert";
+import { bake_model, block_variant, BUILTIN_MODELS, type ModelJson, resolve_texture } from "$/common/block_models.ts";
+import { block_from_json } from "$/common/mod_data.ts";
+import { set_state_value } from "$/common/utils.ts";
+
+const cube = BUILTIN_MODELS["engine:cube"];
+
+Deno.test("cubes resolve the old texture shapes", () => {
+	assertEquals(resolve_texture("#top", "a:all", cube), "a:all");
+	const pillar = { top: "a:top", bottom: "a:bottom", side: "a:side" };
+	assertEquals(["#top", "#bottom", "#front", "#side"].map((t) => resolve_texture(t, pillar, cube)), [
+		"a:top",
+		"a:bottom",
+		"a:side",
+		"a:side",
+	]);
+	const furnace = { front: "a:front", side: "a:side" };
+	assertEquals(["#top", "#bottom", "#front"].map((t) => resolve_texture(t, furnace, cube)), [
+		"a:side",
+		"a:side",
+		"a:front",
+	]);
+	assertEquals(resolve_texture("#nothing", { crop: "a:crop" }), "engine:missing");
+});
+
+Deno.test("a cube bakes into six full faces that cull against their neighbors", () => {
+	const quads = bake_model(cube, "a:all");
+	assertEquals(quads.length, 6);
+	assert(quads.every((q) => q.flush && q.cull === q.face && q.texture === "a:all"));
+	// the top face, corners and uvs like the mesher always had
+	assertEquals(quads[0].positions, [0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0]);
+	assertEquals(quads[0].uvs, [0, 16, 16, 16, 16, 0, 0, 0]);
+});
+
+Deno.test("crop and cross models are planes inside the block, seen from both sides", () => {
+	const crop = bake_model(BUILTIN_MODELS["engine:crop"], { crop: "a:wheat" });
+	assertEquals(crop.length, 8);
+	assert(crop.every((q) => !q.flush && q.cull === -1 && !q.shade && q.texture === "a:wheat"));
+	assertEquals(crop[0].positions.filter((_, i) => i % 3 === 0), [0.25, 0.25, 0.25, 0.25]);
+
+	const cross = bake_model(BUILTIN_MODELS["engine:cross"], { cross: "a:flower" });
+	assertEquals(cross.length, 4);
+	// rescaled so the diagonal planes stay as wide as the block, like minecraft's (0.8 to 15.2 pixels)
+	for (const quad of cross) {
+		for (const v of quad.positions) assert(v > -1e-6 && v < 1 + 1e-6, `${v} is outside the block`);
+	}
+	const xs = cross[0].positions.filter((_, i) => i % 3 === 0).map((v) => Math.round(v * 1000) / 1000);
+	assertEquals(new Set(xs), new Set([0.05, 0.95]));
+});
+
+Deno.test("turning a model moves its faces and cullfaces", () => {
+	const model: ModelJson = {
+		id: "a:half",
+		elements: [{
+			from: [0, 0, 0],
+			to: [16, 16, 8],
+			faces: { north: { texture: "a:x", cullface: "north" } },
+		}],
+	};
+	const [north] = bake_model(model, undefined, 0);
+	const [east] = bake_model(model, undefined, 90);
+	assertEquals([north.face, north.cull], [3, 3]);
+	assertEquals([east.face, east.cull], [5, 5]);
+	assert(east.flush);
+});
+
+Deno.test("variants pick textures by state", () => {
+	const { block } = block_from_json(JSON.parse(Deno.readTextFileSync("mods/bworld/blocks/wheat.json")).block);
+	assertEquals(block_variant(block, { age: 5 }).textures, { crop: "bworld:wheat_stage_5" });
+	assertEquals(block_variant(block, { age: 5 }).model, "engine:crop");
+	assertEquals(block_variant(block).textures, { crop: "bworld:wheat_stage_0" });
+	// states live above the numeric id
+	assertEquals(set_state_value(7, block, "age", 3), (3 << 16) | 7);
+});

tests/mod_loading_test.ts

@@ -3,6 +3,7 @@ import { AIR, CHUNK_HEIGHT } from "$/common/constants.ts";
 import { BlockRegistry, EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";
 import { block_from_json, block_to_json, item_from_json, item_to_json } from "$/common/mod_data.ts";
 import { generate_raw_chunk } from "$/common/generation.ts";
+import { get_state_value } from "$/common/utils.ts";
 import { load_worldgen } from "$/common/worldgen_loader.ts";
 import { create_mod } from "$/tools/new_mod.ts";
 import { PROTOCOL_VERSION } from "$/common/protocol.ts";
@@ -23,9 +24,9 @@ const inventory_of = (messages: Msg[]) =>
 
 Deno.test("the base game loads from mods/bworld", async () => {
 	const { game } = await test_game("mods");
-	assertEquals(EverythingRegistry.entries("blocks").length, 19);
-	// 11 items plus the item forms of the 16 blocks that have one
-	assertEquals(EverythingRegistry.entries("items").length, 27);
+	assertEquals(EverythingRegistry.entries("blocks").length, 20);
+	// 14 items plus the item forms of the 17 blocks that have one
+	assertEquals(EverythingRegistry.entries("items").length, 31);
 	assertEquals(game.recipes.shaped.length, 5);
 	assertEquals(game.recipes.furnace.size, 6);
 	assertEquals(game.recipes.fuel.size, 2);
@@ -34,6 +35,37 @@ Deno.test("the base game loads from mods/bworld", async () => {
 	assert(EverythingRegistry.get<ItemRegistry>("items", "bworld:watering_can")?.on_create);
 });
 
+Deno.test("bone meal grows wheat until it's fully grown", async () => {
+	const { game, take, send } = await test_game("mods");
+	game.on_connect(1);
+	send(1, { type: "hello", name: "alice", protocol: PROTOCOL_VERSION });
+	send(1, { type: "ready" });
+
+	let y = CHUNK_HEIGHT - 1;
+	while (game.world.get_block_nid(1, y, 1) === AIR) y--;
+	y += 1;
+	game.set_block(1, y, 1, "bworld:wheat");
+	const wheat = EverythingRegistry.get<BlockRegistry>("blocks", "bworld:wheat")!;
+	const age = () => get_state_value(game.world.get_block_value(1, y, 1), wheat, "age")!;
+	assertEquals(age(), 0);
+
+	send(1, { type: "chat", text: "/give bworld:bone_meal 8" });
+	const slot = inventory_of(take(1)).findIndex((i: Msg) => i?.id === "bworld:bone_meal");
+	send(1, { type: "select_slot", slot });
+	send(1, { type: "move", x: 2.5, y, z: 2.5, yaw: 0, pitch: 0 });
+
+	// 2 to 5 stages at a time
+	send(1, { type: "use_block", x: 1, y, z: 1, face: "top" });
+	assert(age() >= 2 && age() <= 5, `age ${age()}`);
+	// at most 3 more uses to reach 7, then it stops using bone meal
+	for (let i = 0; i < 5; i++) send(1, { type: "use_block", x: 1, y, z: 1, face: "top" });
+	assertEquals(age(), 7);
+	const left = inventory_of(take(1))[slot]?.count;
+	assert(left >= 4 && left <= 6, `${left} bone meal left`);
+	// nothing got placed on top
+	assertEquals(game.world.get_block_id(1, y + 1, 1), "bworld:air");
+});
+
 Deno.test("mods/bworld json survives going to the registry and back", async () => {
 	await test_game("mods");
 	for (const file of Deno.readDirSync("mods/bworld/blocks")) {

tests/mod_tools_test.ts

@@ -65,6 +65,20 @@ Deno.test("check-mods finds broken mods", async () => {
 		format_version: 1,
 		block: { id: "broken:x", textures: "bworld:stone" },
 	});
+	// a model that doesn't exist, a variant for a state the block doesn't have, and a broken model
+	write_json(`${mod}/blocks/plant.json`, {
+		format_version: 1,
+		block: { id: "broken:plant", textures: { cross: "broken:plant" }, model: "broken:no_such_model" },
+	});
+	write_json(`${mod}/blocks/grows.json`, {
+		format_version: 1,
+		block: { id: "broken:grows", textures: "broken:plant", variants: { "size=1": { y: 90 } } },
+	});
+	Deno.mkdirSync(`${mod}/models`);
+	write_json(`${mod}/models/bad.json`, {
+		format_version: 1,
+		model: { id: "broken:bad", elements: [{ from: [0, 0], to: [16, 16, 16], faces: { up: { texture: "#all" } } }] },
+	});
 	// not json
 	Deno.writeTextFileSync(`${mod}/items/bad.json`, "{ nope");
 	// uses a letter the key doesn't define
@@ -93,6 +107,10 @@ Deno.test("check-mods finds broken mods", async () => {
 	has(report.errors, "item broken:no_such_item doesn't exist");
 	has(report.errors, "block broken:x is also defined by broken, broken");
 	has(report.errors, "items/bad.json: isn't valid json");
+	has(report.errors, "model broken:no_such_model doesn't exist");
+	has(report.errors, `"size=1" must be a state of this block`);
+	has(report.errors, "elements[0].from must be [x, y, z]");
+	has(report.errors, `elements[0].faces: "up" isn't one of`);
 	has(report.errors, `pattern uses "B" but key doesn't define it`);
 	has(report.errors, "textures/huge.png: is");
 	has(report.errors, "scripts don't typecheck");

tools/check_mods.ts

@@ -9,9 +9,11 @@ import {
 	validate_block,
 	validate_item,
 	validate_manifest,
+	validate_model,
 	validate_ore,
 	validate_recipe,
 } from "$/common/mod_data.ts";
+import { BUILTIN_MODELS, type ModelJson } from "$/common/block_models.ts";
 
 export interface ModReport {
 	id: string;
@@ -25,6 +27,7 @@ export interface LoadedMod {
 	report: ModReport;
 	manifest?: Record<string, unknown>;
 	blocks: { file: string; json: BlockJson }[];
+	models: { file: string; json: ModelJson }[];
 	items: { file: string; json: ItemJson }[];
 	recipes: { file: string; json: RecipeJson }[];
 	ores: { file: string; json: OreJson }[];
@@ -99,6 +102,7 @@ function load_mod(mods_dir: string, id: string): LoadedMod {
 		dir,
 		report: { id, errors: [], warnings: [] },
 		blocks: [],
+		models: [],
 		items: [],
 		recipes: [],
 		ores: [],
@@ -147,6 +151,7 @@ function load_mod(mods_dir: string, id: string): LoadedMod {
 		}
 	};
 	load_data("blocks", "block", validate_block, mod.blocks);
+	load_data("models", "model", validate_model, mod.models);
 	load_data("items", "item", validate_item, mod.items);
 	load_data("recipes", "recipe", validate_recipe, mod.recipes);
 
@@ -164,7 +169,7 @@ function load_mod(mods_dir: string, id: string): LoadedMod {
 	}
 
 	// a mod only registers ids in its own namespace
-	for (const { file, json } of [...mod.blocks, ...mod.items]) {
+	for (const { file, json } of [...mod.blocks, ...mod.models, ...mod.items]) {
 		if (json.id.split(":")[0] !== id) error(`${file}: ${json.id} isn't in this mod's namespace "${id}"`);
 	}
 
@@ -186,6 +191,7 @@ function load_mod(mods_dir: string, id: string): LoadedMod {
 function check_references(mods: LoadedMod[]) {
 	const block_owners = new Map<string, string[]>();
 	const item_owners = new Map<string, string[]>();
+	const model_owners = new Map<string, string[]>();
 	const add = (map: Map<string, string[]>, id: string, mod: string) => map.set(id, [...(map.get(id) ?? []), mod]);
 
 	const textures = new Set<string>();
@@ -199,6 +205,7 @@ function check_references(mods: LoadedMod[]) {
 			if (json.item !== false) add(item_owners, json.id, mod.id);
 		}
 		for (const { json } of mod.items) add(item_owners, json.id, mod.id);
+		for (const { json } of mod.models) add(model_owners, json.id, mod.id);
 		for (const texture of mod.textures) textures.add(texture);
 	}
 
@@ -213,12 +220,14 @@ function check_references(mods: LoadedMod[]) {
 			if (!mod_ids.has(dep)) errors.push(`manifest.json: depends on "${dep}", which isn't installed`);
 		}
 
-		const uses = (file: string, id: string, what: "block" | "item" | "texture") => {
+		const uses = (file: string, id: string, what: "block" | "item" | "texture" | "model") => {
 			const namespace = id.split(":")[0];
 			if (namespace !== mod.id && namespace !== "engine" && !dependencies.has(namespace)) {
 				warnings.push(`${file}: uses ${id} but doesn't list "${namespace}" in dependencies`);
 			}
-			if (what === "texture") {
+			if (what === "model") {
+				if (!BUILTIN_MODELS[id] && !model_owners.has(id)) errors.push(`${file}: model ${id} doesn't exist`);
+			} else if (what === "texture") {
 				if (!textures.has(id)) warnings.push(`${file}: texture ${id} doesn't exist, it will show as missing`);
 			} else if (!(what === "block" ? block_owners : item_owners).has(id)) {
 				errors.push(`${file}: ${what} ${id} doesn't exist`);
@@ -229,10 +238,28 @@ function check_references(mods: LoadedMod[]) {
 			if ((block_owners.get(json.id)?.length ?? 0) > 1) {
 				errors.push(`${file}: block ${json.id} is also defined by ${block_owners.get(json.id)!.join(", ")}`);
 			}
-			const texture_ids = typeof json.textures === "string" ? [json.textures] : Object.values(json.textures);
-			for (const texture of texture_ids) uses(file, texture, "texture");
+			for (const variant of [json, ...Object.values(json.variants ?? {})]) {
+				if (variant.model) uses(file, variant.model, "model");
+				const textures = variant.textures ?? {};
+				for (const texture of typeof textures === "string" ? [textures] : Object.values(textures)) {
+					uses(file, texture, "texture");
+				}
+			}
 			if (json.drops) uses(file, json.drops, "item");
 		}
+		for (const { file, json } of mod.models) {
+			if ((model_owners.get(json.id)?.length ?? 0) > 1 || BUILTIN_MODELS[json.id]) {
+				errors.push(`${file}: model ${json.id} is defined more than once`);
+			}
+			for (const texture of Object.values(json.textures ?? {})) {
+				if (!texture.startsWith("#")) uses(file, texture, "texture");
+			}
+			for (const element of json.elements) {
+				for (const face of Object.values(element.faces)) {
+					if (face && !face.texture.startsWith("#")) uses(file, face.texture, "texture");
+				}
+			}
+		}
 		for (const { file, json } of mod.items) {
 			if ((item_owners.get(json.id)?.length ?? 0) > 1) {
 				errors.push(`${file}: item ${json.id} is also defined by ${item_owners.get(json.id)!.join(", ")}`);