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Fix terrain streaming and surface spawning

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This commit is contained in:
Master290 2026-07-21 11:11:19 +03:00
parent f0279cdb65
commit 2b07d6be20
17 changed files with 424 additions and 111 deletions
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7
README.md
View file

@ -37,12 +37,15 @@ block editing, persistent worlds, and an overworld generator built on the real
```
go build ./...
go run ./cmd/regionio -seed 12345
go run ./cmd/regionio -seed 12345 -port 25565 -viewdistance 2
```
The world seed defaults to `0`; override it with the `-seed` flag or the
`REGIONIO_SEED` environment variable. The server listens on `0.0.0.0:25565`.
Changing the seed for an existing world directory is rejected.
Changing the seed for an existing world directory is rejected. The server caps
the client-requested chunk radius at `2` by default because cold density-based
generation is expensive; raise it with `-viewdistance 3` after the surrounding
world has been generated and cached.
## Testing

7
cmd/regionio/main.go
View file

@ -27,13 +27,18 @@ func main() {
// fatal — a wrong seed silently generates a different world than intended.
seedFlag := flag.Int64("seed", parseSeedEnv(os.Getenv("REGIONIO_SEED"), cfg.WorldSeed, log),
"world seed (overrides REGIONIO_SEED)")
port := flag.Int("port", cfg.Port, "TCP listen port")
worldDir := flag.String("world", cfg.WorldDir, "world directory (empty = in-memory only)")
maxCache := flag.Int("maxcache", cfg.MaxCachedChunks, "max cached chunks, LRU eviction (0 = unbounded)")
viewDistance := flag.Int("viewdistance", cfg.MaxViewDistance, "maximum client chunk view radius (2-16)")
flag.Parse()
cfg.WorldSeed = *seedFlag
cfg.Port = *port
cfg.WorldDir = *worldDir
cfg.MaxCachedChunks = *maxCache
log.Info("using world seed", "seed", cfg.WorldSeed, "worldDir", cfg.WorldDir, "maxcache", cfg.MaxCachedChunks)
cfg.MaxViewDistance = *viewDistance
log.Info("using world seed", "seed", cfg.WorldSeed, "worldDir", cfg.WorldDir,
"maxcache", cfg.MaxCachedChunks, "viewdistance", cfg.MaxViewDistance)
srv, err := server.New(cfg)
if err != nil {

10
internal/network/configuration.go
View file

@ -98,15 +98,15 @@ func (h *handler) handleClientInformation(pkt protocol.Packet) error {
return err
}
// view_distance drives the chunk streamer radius. The client sends 2..32;
// clamp into a sane server range so a huge view distance doesn't trigger a
// generation explosion.
// view_distance drives the chunk streamer radius. The server owns the upper
// bound because accepting the client's render distance can multiply cold
// generation work into hundreds of chunks.
vdInt := int(int8(vd))
if vdInt < 2 {
vdInt = 2
}
if vdInt > 16 {
vdInt = 16
if max := h.srv.Config().MaxViewDistance; vdInt > max {
vdInt = max
}
h.viewDistance = vdInt

1
internal/network/handler.go
View file

@ -31,6 +31,7 @@ type handler struct {
session *server.PlayerSession
knownPlayers map[[16]byte]bool
knownEntities map[int32]visibleEntity
spawnY float64
// Creative inventory state for block placement.
heldSlot int32 // selected hotbar index (0-8)

8
internal/network/multiplayer_test.go
View file

@ -150,11 +150,13 @@ func TestBoundaryEditBroadcastsEveryChangedLightChunk(t *testing.T) {
srv.SetPlayerViewDistance(h.session, 2)
valid, lightChunks := cache.SetBlockWithLight(15, 100, 8, world.StateGlowstone)
if !valid || len(lightChunks) != 2 {
t.Fatalf("boundary edit valid=%v light chunks=%v; want two", valid, lightChunks)
if !valid || len(lightChunks) != 6 {
t.Fatalf("boundary edit valid=%v light chunks=%v; want six cached neighbors", valid, lightChunks)
}
h.broadcastBlockUpdate(15, 100, 8, world.StateGlowstone, lightChunks)
assertPacketIDs(t, recorder.take(t), protocol.PlayBlockUpdate, protocol.PlayLightUpdate, protocol.PlayLightUpdate)
assertPacketIDs(t, recorder.take(t), protocol.PlayBlockUpdate,
protocol.PlayLightUpdate, protocol.PlayLightUpdate, protocol.PlayLightUpdate,
protocol.PlayLightUpdate, protocol.PlayLightUpdate, protocol.PlayLightUpdate)
}
func TestIntegrationFourClientsVisibilityMovementLeaveAndLight(t *testing.T) {

29
internal/network/play.go
View file

@ -12,11 +12,10 @@ import (
"regionio/internal/world"
)
// Spawn coordinates. Y sits above the maximum terrain height so the player
// drops onto the generated surface rather than spawning inside it.
// Spawn column. The feet-level Y is resolved from the generated surface when
// the player enters the play phase.
const (
spawnX = 8.5
spawnY = 200.0
spawnZ = 8.5
)
@ -29,7 +28,12 @@ func (h *handler) beginPlay() error {
return err
}
h.session = session
h.srv.SetPlayerTransform(session, spawnX, spawnY, spawnZ, 0, 0, true)
spawnY, ok := h.srv.Chunks().SafeSpawnY(int(math.Floor(spawnX)), int(math.Floor(spawnZ)))
if !ok {
spawnY = world.SeaLevel + 1
}
h.spawnY = float64(spawnY)
h.srv.SetPlayerTransform(session, spawnX, h.spawnY, spawnZ, 0, 0, true)
h.srv.SetPlayerViewDistance(session, h.visibilityRadius())
for i := range h.hotbar {
h.hotbar[i] = -1 // empty
@ -56,7 +60,7 @@ func (h *handler) beginPlay() error {
}
// Launch the background chunk streamer. It owns generation + sending so the
// read loop stays free; requestRecenter is a non-blocking push.
h.streamer = newStreamer(h.srv.Chunks(), h.conn, h.log, h.viewDistance)
h.streamer = newStreamer(h.srv.Chunks(), h.conn, h.log, h.visibilityRadius())
go h.streamer.run(h.ctx)
h.streamer.requestRecenter(0, 0)
go h.keepAliveLoop()
@ -76,7 +80,7 @@ func (h *handler) sendDefaultSpawnPosition() error {
// yaw and pitch. GlobalPos starts with the dimension resource key.
w := protocol.NewWriter(40)
w.String("minecraft:overworld")
w.Position(8, 100, 8)
w.Position(8, int(math.Floor(h.spawnY)), 8)
w.Float32(0.0)
w.Float32(0.0)
return h.conn.SendWriter(protocol.PlayDefaultSpawnPos, w)
@ -109,13 +113,14 @@ func (h *handler) onPlayerMove(x, y, z float64, yaw, pitch float32, onGround boo
}
func (h *handler) visibilityRadius() int {
if h.viewDistance < 2 {
return defaultViewRadius
distance := h.viewDistance
if distance < 2 {
distance = defaultViewRadius
}
if h.viewDistance > 16 {
return 16
if max := h.srv.Config().MaxViewDistance; distance > max {
distance = max
}
return h.viewDistance
return distance
}
// sendPlayLogin writes the clientbound play "login" packet. Field layout was
@ -176,7 +181,7 @@ func (h *handler) sendGameEvent(event byte, value float32) error {
func (h *handler) sendPlayerPosition(teleportID int32) error {
w := protocol.NewWriter(64)
w.VarInt(teleportID)
w.Float64(spawnX).Float64(spawnY).Float64(spawnZ) // position
w.Float64(spawnX).Float64(h.spawnY).Float64(spawnZ) // position
w.Float64(0).Float64(0).Float64(0) // velocity
w.Float32(0) // yaw
w.Float32(0) // pitch

19
internal/network/play_spawn_test.go
View file

@ -1,14 +1,17 @@
package network
import (
"log/slog"
"testing"
"regionio/internal/protocol"
"regionio/internal/server"
"regionio/internal/world"
)
func TestSendDefaultSpawnPositionLayout(t *testing.T) {
recorder := &recordingConn{}
h := &handler{conn: NewConn(recorder)}
h := &handler{conn: NewConn(recorder), spawnY: 100}
if err := h.sendDefaultSpawnPosition(); err != nil {
t.Fatal(err)
@ -38,3 +41,17 @@ func TestSendDefaultSpawnPositionLayout(t *testing.T) {
t.Fatalf("remaining bytes = %d, want 0", remaining)
}
}
func TestVisibilityRadiusUsesServerLimit(t *testing.T) {
cfg := server.DefaultConfig()
cfg.WorldDir = ""
cfg.MaxViewDistance = 2
srv, err := server.NewWithCache(cfg, world.NewCache(-1, world.GenerateFlat))
if err != nil {
t.Fatal(err)
}
h := &handler{srv: srv, log: slog.Default(), viewDistance: 16}
if got := h.visibilityRadius(); got != 2 {
t.Fatalf("visibility radius = %d, want server limit 2", got)
}
}

74
internal/network/streamer.go
View file

@ -48,8 +48,9 @@ type streamer struct {
}
// defaultViewRadius is used when the client hasn't sent client_information or
// sent an implausible value. Matches the legacy chunkRadius.
const defaultViewRadius = 4
// sent an implausible value. Vanilla generation is expensive, so keep the cold
// start bounded until nearby terrain has warmed in the cache.
const defaultViewRadius = 2
// newStreamer constructs a streamer for the given cache/conn. viewDistance comes
// from the client's client_information (clamped to a safe range); genRadius is
@ -161,6 +162,13 @@ func (s *streamer) processRecenter(ctx context.Context, cx, cz int32) (recenterR
s.tickets.Replace(viewTickets, prefetchTickets)
}
// The center frame needs a 3x3 terrain neighborhood for lighting. Preload
// those chunks concurrently so the first visible chunk is not delayed by
// eight sequential generator calls inside the lighting pass.
if !s.loaded[[2]int32{cx, cz}] {
s.parallelPreload(ctx, spiralOrder(cx, cz, 1))
}
// Client residency follows viewRadius exactly. The prefetch ring is retained
// only server-side by tickets and never left loaded on the client.
for key := range s.loaded {
@ -175,7 +183,8 @@ func (s *streamer) processRecenter(ctx context.Context, cx, cz int32) (recenterR
if next, superseded := s.streamPriority(ctx, cx, cz, toSend, true); superseded {
return next, true
}
// Pre-generate the ring so the next recenter finds frames warm in the cache.
// Preload terrain only. Building full frames here would calculate lighting
// for off-screen chunks and recursively generate yet another outer ring.
if next, superseded := s.streamPriority(ctx, cx, cz, toPreGen, false); superseded {
return next, true
}
@ -207,7 +216,7 @@ func (s *streamer) streamPriority(ctx context.Context, cx, cz int32, keys [][2]i
if send {
s.parallelSend(ctx, keys[start:end])
} else {
s.parallelGenerate(ctx, keys[start:end])
s.parallelPreload(ctx, keys[start:end])
}
if next, ok := s.latestRecenter(); ok {
return next, true
@ -255,8 +264,8 @@ func (s *streamer) sendForgetLevelChunk(cx, cz int32) {
_ = s.conn.SendWriter(protocol.PlayForgetLevelChunk, w)
}
// parallelSend generates the given chunks across the worker pool and sends each
// frame as soon as it is ready (order is best-effort; the client reassembles).
// parallelSend generates the given chunks across the worker pool, then sends
// them in caller order so the client receives a contiguous near-first view.
// Already-loaded chunks are skipped. Returns when all are sent or ctx cancels.
func (s *streamer) parallelSend(ctx context.Context, keys [][2]int32) {
var pending []frameJob
@ -304,13 +313,26 @@ func (s *streamer) parallelSend(ctx context.Context, keys [][2]int32) {
wg.Wait()
close(results)
}()
generated := make(map[[2]int32]frameResult, len(pending))
failed := false
for r := range results {
if r.err != nil {
// Send failed — the connection is likely closing. Bail out; the
// serve loop will tear us down via ctx cancel.
if s.log != nil {
s.log.Debug("streamer frame failed", "cx", r.cx, "cz", r.cz, "err", r.err)
}
failed = true
continue
}
generated[[2]int32{r.cx, r.cz}] = r
}
if failed {
return
}
// Generation completes out of order, but client presentation should not.
// Emit the contiguous spiral order supplied by the caller.
for _, j := range pending {
r, ok := generated[[2]int32{j.cx, j.cz}]
if !ok {
return
}
if s.conn != nil {
@ -321,13 +343,13 @@ func (s *streamer) parallelSend(ctx context.Context, keys [][2]int32) {
return
}
}
s.loaded[[2]int32{r.cx, r.cz}] = true
s.loaded[[2]int32{j.cx, j.cz}] = true
}
}
// parallelGenerate warms the cache for the given chunks without sending them
// (used for the predictive ring). Errors are ignored.
func (s *streamer) parallelGenerate(ctx context.Context, keys [][2]int32) {
// parallelPreload warms terrain for the given chunks without calculating light,
// encoding frames, or sending packets. Errors are ignored.
func (s *streamer) parallelPreload(ctx context.Context, keys [][2]int32) {
var pending []frameJob
for _, k := range keys {
if s.loaded[k] {
@ -355,7 +377,7 @@ func (s *streamer) parallelGenerate(ctx context.Context, keys [][2]int32) {
return
default:
}
_, _ = s.cache.FrameErrContext(ctx, j.cx, j.cz) // warm cache; discard frame
_ = s.cache.PreloadErrContext(ctx, j.cx, j.cz)
}
}()
}
@ -381,8 +403,8 @@ type frameResult struct {
err error
}
// generateWorker reads jobs, generates+frames the chunk via the (thread-safe)
// cache, and sends the frame to the conn. It exits when jobs closes.
// generateWorker reads jobs and generates+frames chunks via the thread-safe
// cache. It exits when jobs closes.
func (s *streamer) generateWorker(ctx context.Context, jobs <-chan frameJob, results chan<- frameResult) {
for j := range jobs {
select {
@ -407,9 +429,7 @@ func (s *streamer) generateWorker(ctx context.Context, jobs <-chan frameJob, res
}
// spiralOrder returns chunk coordinates in a square of side (2*radius+1) around
// (cx, cz), ordered from the centre outward (Chebyshev rings). The centre is
// first, then ring 1, ring 2, … ring `radius`. Within a ring the order is
// deterministic but not otherwise constrained — nearest-first is what matters.
// (cx, cz), ordered from the centre outward in contiguous Chebyshev rings.
func spiralOrder(cx, cz int32, radius int) [][2]int32 {
if radius < 0 {
radius = 0
@ -417,14 +437,18 @@ func spiralOrder(cx, cz int32, radius int) [][2]int32 {
out := make([][2]int32, 0, (2*radius+1)*(2*radius+1))
out = append(out, [2]int32{cx, cz})
for r := 1; r <= radius; r++ {
// Walk the perimeter of the ring at Chebyshev distance r.
for d := -r; d <= r; d++ {
out = append(out, [2]int32{cx + int32(d), cz - int32(r)}) // top edge
out = append(out, [2]int32{cx + int32(d), cz + int32(r)}) // bottom edge
// Walk one continuous perimeter: top, right, bottom, left.
for x := -r; x <= r; x++ {
out = append(out, [2]int32{cx + int32(x), cz - int32(r)})
}
for d := -r + 1; d <= r-1; d++ {
out = append(out, [2]int32{cx - int32(r), cz + int32(d)}) // left edge
out = append(out, [2]int32{cx + int32(r), cz + int32(d)}) // right edge
for z := -r + 1; z <= r; z++ {
out = append(out, [2]int32{cx + int32(r), cz + int32(z)})
}
for x := r - 1; x >= -r; x-- {
out = append(out, [2]int32{cx + int32(x), cz + int32(r)})
}
for z := r - 1; z >= -r+1; z-- {
out = append(out, [2]int32{cx - int32(r), cz + int32(z)})
}
}
return out

26
internal/network/streamer_test.go
View file

@ -69,6 +69,28 @@ func TestSpiralOrderRingStructure(t *testing.T) {
}
}
func TestSpiralOrderWalksEachRingContiguously(t *testing.T) {
order := spiralOrder(0, 0, 4)
for i := 1; i < len(order); i++ {
previousRing := chunkDistanceFrom(0, 0, order[i-1])
currentRing := chunkDistanceFrom(0, 0, order[i])
if previousRing != currentRing {
continue
}
dx := order[i][0] - order[i-1][0]
if dx < 0 {
dx = -dx
}
dz := order[i][1] - order[i-1][1]
if dz < 0 {
dz = -dz
}
if dx+dz != 1 {
t.Fatalf("ring %d jumps from %v to %v", currentRing, order[i-1], order[i])
}
}
}
// TestRequestRecenterNonBlocking confirms requestRecenter never blocks the
// caller even when many requests are pushed rapidly (the streamer drains stale
// ones). This is the property the read loop relies on to stay responsive.
@ -104,6 +126,7 @@ func TestStreamerSendsStrictlyNearFirst(t *testing.T) {
lastDistance := int32(-1)
chunks := 0
wantOrder := spiralOrder(7, -3, 2)
for _, packet := range recorder.take(t) {
if packet.ID != protocol.PlayLevelChunk {
continue
@ -122,6 +145,9 @@ func TestStreamerSendsStrictlyNearFirst(t *testing.T) {
t.Fatalf("chunk (%d,%d) at distance %d arrived after distance %d", x, z, distance, lastDistance)
}
lastDistance = distance
if want := wantOrder[chunks]; x != want[0] || z != want[1] {
t.Fatalf("chunk[%d] = (%d,%d), want %v", chunks, x, z, want)
}
chunks++
}
if chunks != 25 {

8
internal/server/server.go
View file

@ -32,6 +32,10 @@ type Config struct {
// MaxCachedChunks bounds the in-memory chunk+frame cache (LRU). 0 means
// unbounded (use only for tests/flat worlds). At ~200KiB/chunk, 1024 ≈ 200MB.
MaxCachedChunks int
// MaxViewDistance caps the client-requested chunk radius. Generation is much
// more expensive than vanilla's pregenerated worlds, so the server owns the
// upper bound instead of accepting the client's render distance verbatim.
MaxViewDistance int
}
// DefaultConfig returns sensible defaults matching vanilla expectations.
@ -51,6 +55,7 @@ func DefaultConfig() Config {
// MaxCachedChunks keeps the live cache near 200MB at the default; the
// streamer's pre-gen ring and player view distance comfortably fit.
MaxCachedChunks: 1024,
MaxViewDistance: 2,
}
}
@ -143,6 +148,9 @@ func validateConfig(cfg Config) error {
if cfg.MaxCachedChunks < 0 {
return fmt.Errorf("server: max cached chunks must not be negative")
}
if cfg.MaxViewDistance < 2 || cfg.MaxViewDistance > 16 {
return fmt.Errorf("server: max view distance must be between 2 and 16")
}
return nil
}

57
internal/server/spawner.go
View file

@ -19,6 +19,7 @@ func (s *Server) StartSpawning(ctx context.Context) {
func (s *Server) entityTickLoop(ctx context.Context) {
ticker := time.NewTicker(50 * time.Millisecond) // 20 TPS
defer ticker.Stop()
rng := rand.New(rand.NewSource(time.Now().UnixNano()))
for {
select {
case <-ctx.Done():
@ -55,9 +56,9 @@ func (s *Server) entityTickLoop(ctx context.Context) {
}
} else {
// Random wander
e.X += (rand.Float64() - 0.5) * 0.2
e.Z += (rand.Float64() - 0.5) * 0.2
e.Yaw += float32((rand.Float64() - 0.5) * 10.0)
e.X += (rng.Float64() - 0.5) * 0.2
e.Z += (rng.Float64() - 0.5) * 0.2
e.Yaw += float32((rng.Float64() - 0.5) * 10.0)
}
}
@ -73,6 +74,7 @@ func (s *Server) entityTickLoop(ctx context.Context) {
func (s *Server) mobSpawnLoop(ctx context.Context) {
ticker := time.NewTicker(2 * time.Second)
defer ticker.Stop()
rng := rand.New(rand.NewSource(time.Now().UnixNano()))
pigType := registry.EntityTypeIndex("minecraft:pig")
zombieType := registry.EntityTypeIndex("minecraft:zombie")
@ -85,28 +87,41 @@ func (s *Server) mobSpawnLoop(ctx context.Context) {
case <-ctx.Done():
return
case <-ticker.C:
if s.PlayerCount() == 0 || s.entities.Count() >= 50 {
continue // limit to 50 entities
if s.PlayerCount() == 0 || s.entities.Count() >= 20 {
continue
}
s.spawnMobNearPlayer(rng, pigType, zombieType)
}
}
}
// Spawn near the spawn point (8.5, 200, 8.5)
x := (rand.Float64() - 0.5) * 30.0
z := (rand.Float64() - 0.5) * 30.0
t := pigType
name := "minecraft:pig"
if rand.Float32() < 0.5 {
t = zombieType
name = "minecraft:zombie"
func (s *Server) spawnMobNearPlayer(rng *rand.Rand, pigType, zombieType int) bool {
players := s.PlayerSnapshots()
if len(players) == 0 {
return false
}
player := players[rng.Intn(len(players))]
angle := rng.Float64() * 2 * math.Pi
distance := 16.0 + rng.Float64()*16.0
x := int(math.Floor(player.X + math.Cos(angle)*distance))
z := int(math.Floor(player.Z + math.Sin(angle)*distance))
y, ok := s.chunks.SafeSpawnY(x, z)
if !ok {
return false
}
typeID := pigType
typeName := "minecraft:pig"
if rng.Float32() < 0.5 {
typeID = zombieType
typeName = "minecraft:zombie"
}
s.entities.Add(&world.Entity{
TypeID: t,
TypeName: name,
X: x + 8.5,
Y: 200.0,
Z: z + 8.5,
TypeID: typeID,
TypeName: typeName,
X: float64(x) + 0.5,
Y: float64(y),
Z: float64(z) + 0.5,
})
}
}
return true
}

39
internal/server/spawner_test.go Normal file
View file

@ -0,0 +1,39 @@
package server
import (
"math"
"math/rand"
"testing"
"regionio/internal/world"
)
func TestSpawnMobNearPlayerUsesSurface(t *testing.T) {
cfg := DefaultConfig()
cfg.WorldDir = ""
srv, err := NewWithCache(cfg, world.NewCache(-1, world.GenerateFlat))
if err != nil {
t.Fatal(err)
}
session, err := srv.RegisterPlayer(Profile{Name: "Alice", UUID: OfflineUUID("Alice")}, nil)
if err != nil {
t.Fatal(err)
}
srv.SetPlayerTransform(session, 8.5, 80, 8.5, 0, 0, true)
if !srv.spawnMobNearPlayer(rand.New(rand.NewSource(1)), 10, 20) {
t.Fatal("spawnMobNearPlayer returned false")
}
entities := srv.Entities().All()
if len(entities) != 1 {
t.Fatalf("entities = %d, want 1", len(entities))
}
entity := entities[0]
if entity.Y != world.FlatSurfaceY+1 {
t.Fatalf("mob Y = %v, want surface Y %d", entity.Y, world.FlatSurfaceY+1)
}
distance := math.Hypot(entity.X-8.5, entity.Z-8.5)
if distance < 15 || distance > 33 {
t.Fatalf("mob distance = %v, want near player", distance)
}
}

45
internal/world/cache.go
View file

@ -40,7 +40,7 @@ type Cache struct {
maxChunks int // LRU capacity; 0 = unbounded
mu sync.Mutex
lightMu sync.Mutex
lightMu sync.RWMutex
chunks map[[2]int32]*Chunk
frames map[[2]int32][]byte
dirty map[[2]int32]uint64
@ -248,6 +248,22 @@ func (c *Cache) FrameErrContext(ctx context.Context, cx, cz int32) ([]byte, erro
return c.frameErr(cx, cz)
}
// PreloadErrContext loads or generates a chunk without calculating lighting or
// encoding a network frame. Streamers use it for predictive terrain work so a
// prefetch ring does not recursively expand through lighting neighborhoods.
func (c *Cache) PreloadErrContext(ctx context.Context, cx, cz int32) error {
select {
case c.frameSlots <- struct{}{}:
defer func() { <-c.frameSlots }()
case <-ctx.Done():
return ctx.Err()
}
release := c.beginUse([2]int32{cx, cz})
defer release()
_, err := c.chunkAtErr(cx, cz)
return err
}
func (c *Cache) frameErr(cx, cz int32) ([]byte, error) {
key := [2]int32{cx, cz}
@ -307,6 +323,33 @@ func (c *Cache) GetBlock(x, y, z int) uint16 {
return ch.GetBlock(x, y, z)
}
// SafeSpawnY returns a feet-level Y with a supporting floor and two air blocks
// above it. Water columns and decorative plants are skipped rather than
// spawning an entity inside them. Loading happens once for the whole column.
func (c *Cache) SafeSpawnY(x, z int) (int, bool) {
cx := int32(x >> 4)
cz := int32(z >> 4)
release := c.beginUse([2]int32{cx, cz})
defer release()
ch, err := c.chunkAtErr(cx, cz)
if err != nil {
return 0, false
}
ch.mu.RLock()
defer ch.mu.RUnlock()
for y := MinY + WorldHeight - 3; y >= MinY; y-- {
floor := ch.getBlock(x, y, z)
if !supportsEntitySpawn(floor) {
continue
}
if ch.getBlock(x, y+1, z) == StateAir && ch.getBlock(x, y+2, z) == StateAir {
return y + 1, true
}
}
return 0, false
}
// LightUpdate returns the standalone light_update body for a loaded chunk.
func (c *Cache) LightUpdate(cx, cz int32) ([]byte, error) {
release := c.beginUse([2]int32{cx, cz})

25
internal/world/cache_light.go
View file

@ -10,8 +10,8 @@ import (
// neighborhood. Light attenuates to zero within 15 blocks, so chunks outside
// that neighborhood cannot affect the center chunk.
func (c *Cache) ensureLight(chunk *Chunk) error {
c.lightMu.Lock()
defer c.lightMu.Unlock()
c.lightMu.RLock()
defer c.lightMu.RUnlock()
return c.ensureLightLocked(chunk)
}
@ -65,11 +65,15 @@ func (c *Cache) ensureLightLocked(chunk *Chunk) error {
}
}
// lightInputSnapshot returns blocks for a neighboring chunk without inserting
// a cache miss into the LRU. This keeps lighting correct even for very small
// cache limits and avoids an eight-chunk eviction cascade per frame.
// lightInputSnapshot returns a stable neighbor snapshot. Cache misses are kept
// in the LRU so adjacent frames reuse the same expensive terrain instead of
// regenerating up to eight neighbors for every lighting calculation.
func (c *Cache) lightInputSnapshot(cx, cz int32) (*Chunk, error) {
key := [2]int32{cx, cz}
// A cache smaller than the required 3x3 neighborhood cannot retain these
// inputs usefully. Keep misses detached to avoid evicting the requested
// center chunk and churning the LRU on every frame.
if c.maxChunks > 0 && c.maxChunks < 9 {
c.mu.Lock()
if chunk := c.chunks[key]; chunk != nil {
c.touch(key)
@ -87,7 +91,6 @@ func (c *Cache) lightInputSnapshot(cx, cz int32) (*Chunk, error) {
return snapshot, nil
}
c.mu.Unlock()
if c.store != nil {
loaded, err := c.store.LoadChunk(cx, cz)
if err == nil {
@ -106,6 +109,16 @@ func (c *Cache) lightInputSnapshot(cx, cz int32) (*Chunk, error) {
return snapshot, nil
}
release := c.beginUse(key)
defer release()
chunk, err := c.chunkAtErr(cx, cz)
if err != nil {
return nil, fmt.Errorf("world: load light neighbor (%d,%d): %w", cx, cz, err)
}
snapshot, _ := chunk.snapshot()
return snapshot, nil
}
func (c *Cache) cachedLightNeighborhood(cx, cz int32) map[[2]int32]*Chunk {
c.mu.Lock()
defer c.mu.Unlock()

35
internal/world/cache_light_reuse_test.go Normal file
View file

@ -0,0 +1,35 @@
package world
import (
"sync"
"testing"
)
func TestAdjacentFramesReuseGeneratedLightNeighbors(t *testing.T) {
var mu sync.Mutex
generated := make(map[[2]int32]int)
cache := NewCache(-1, func(cx, cz int32) *Chunk {
mu.Lock()
generated[[2]int32{cx, cz}]++
mu.Unlock()
return NewChunk(cx, cz, BiomePlains)
})
if _, err := cache.FrameErr(0, 0); err != nil {
t.Fatal(err)
}
if _, err := cache.FrameErr(1, 0); err != nil {
t.Fatal(err)
}
mu.Lock()
defer mu.Unlock()
if len(generated) != 12 {
t.Fatalf("generated chunks = %d, want 12 shared neighborhood chunks", len(generated))
}
for pos, count := range generated {
if count != 1 {
t.Fatalf("chunk %v generated %d times, want once", pos, count)
}
}
}

41
internal/world/spawn_surface_test.go Normal file
View file

@ -0,0 +1,41 @@
package world
import "testing"
func TestSafeSpawnYUsesGeneratedSurface(t *testing.T) {
cache := NewCache(-1, GenerateFlat)
y, ok := cache.SafeSpawnY(8, 8)
if !ok || y != FlatSurfaceY+1 {
t.Fatalf("SafeSpawnY = %d, %v; want %d, true", y, ok, FlatSurfaceY+1)
}
}
func TestSafeSpawnYRejectsUnderwaterColumn(t *testing.T) {
cache := NewCache(-1, func(cx, cz int32) *Chunk {
chunk := NewChunk(cx, cz, BiomePlains)
chunk.setBlockRaw(8, 60, 8, StateStone)
for y := 61; y <= SeaLevel; y++ {
chunk.setBlockRaw(8, y, 8, StateWater)
}
return chunk
})
if y, ok := cache.SafeSpawnY(8, 8); ok {
t.Fatalf("SafeSpawnY = %d, true; want underwater column rejected", y)
}
}
func TestSafeSpawnYAcceptsNonOpaqueSolidFloor(t *testing.T) {
stairs := nameToStateID("minecraft:oak_stairs", nil)
if stairs == StateAir {
t.Fatal("oak stairs state is unavailable")
}
cache := NewCache(-1, func(cx, cz int32) *Chunk {
chunk := NewChunk(cx, cz, BiomePlains)
chunk.setBlockRaw(8, 70, 8, stairs)
return chunk
})
y, ok := cache.SafeSpawnY(8, 8)
if !ok || y != 71 {
t.Fatalf("SafeSpawnY = %d, %v; want 71, true for stairs", y, ok)
}
}

36
internal/world/state_names.go
View file

@ -3,6 +3,7 @@ package world
import (
_ "embed"
"encoding/json"
"strings"
"sync"
"regionio/internal/nbt"
@ -39,6 +40,41 @@ func stateByID(id uint16) (stateName, bool) {
return s, ok
}
// supportsEntitySpawn distinguishes collision floors from decorative blocks.
// Light opacity is not sufficient here: stairs and slabs can have opacity zero
// while still supporting an entity.
func supportsEntitySpawn(id uint16) bool {
if id == StateAir || id == StateWater {
return false
}
if lightOpacity(id) > 0 {
return true
}
state, ok := stateByID(id)
if !ok {
return false
}
name := state.Name
for _, suffix := range []string{
"_sapling", "_flower", "_tulip", "_mushroom", "_torch",
"_rail", "_button", "_pressure_plate", "_carpet", "_banner",
"_sign", "_hanging_sign",
} {
if strings.HasSuffix(name, suffix) {
return false
}
}
switch name {
case "minecraft:short_grass", "minecraft:tall_grass", "minecraft:fern",
"minecraft:large_fern", "minecraft:dead_bush", "minecraft:dandelion",
"minecraft:poppy", "minecraft:allium", "minecraft:azure_bluet",
"minecraft:oxeye_daisy", "minecraft:cornflower",
"minecraft:lily_of_the_valley", "minecraft:sunflower":
return false
}
return true
}
func buildStateTable() {
var blocks map[string]struct {
States []struct {