render3d: place_rec.ludic, the one encoder and decoder of a baked placement

prec_put / prec_get / prec_size (Physics' spec): PREC_FULL, 12 bytes, for trees, boulders and stones
(u16 x, z in 1/65536 of the chunk; u16 y in cm above y_base; u8 scale over the kind's lo..hi, yaw, seed,
wind), and PREC_PACKED, 7 bytes, for the stream kinds (56 bits, least significant first: x 12, z 12,
y 12 in cm, scale 6, yaw 6, seed 4, wind 4). An encode takes the cell a value falls in, a decode its
centre, so a round trip is stable; a record is read from a []byte at an offset, never a pointer.
stream_emit_baked and layer_chunk_put take (recs, at, fmt) and decode through it; the earlier sb7_*
pair is gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.render3d/env.ludic

@@ -829,6 +829,7 @@ export state Render3dState {
   ter_ortho_tex: int = 0            # a photograph of the same window, draped with distance
   ter_carpet: int = 0               # the distant-grass carpet (carpet_bake), 0 = none
   ter_shadow_tex: int = 0           # height-field sun shadow: R32F, the lowest lit height
+  sb_rec: floats = floats(8)        # one decoded baked record, reused (stream_baked.ludic)
   tt_dir: string = ""               # terrain_tiles_to: where a map's tiles are written ("" keeps the whole copies)
   tt_key: string = ""
   tt_file: pointer = null           # the tiles' file, open for reading (terrain_tiles.ludic)

packages/ludic.render3d/layer_chunks.ludic

@@ -1,9 +1,6 @@
 # layer_chunks.ludic — a fixed layer (trees, boulders, stones) held as the baked chunks that are in, not
 # the whole map: a slab per chunk in the layer's instance list, put when the ring brings the chunk in
-# and dropped when it goes, the list re-uploaded at most once a frame. A record is 12 bytes: u16 x, u16 z
-# (1/65536 of the chunk), u16 y (cm above y_base), u8 scale (the kind's lo..hi), u8 yaw, u8 seed, u8 wind.
-
-const LC_REC: int = 12
+# and dropped when it goes, the list re-uploaded at most once a frame. A record's layout is place_rec.ludic's.
 
 # the layer made ready for chunks of an n x n grid: its slab index, once at map load, and nothing in it
 @alloc_ok("a map being loaded: a layer's chunk index, once")
@@ -12,30 +9,23 @@ export function layer_chunks_begin(l: Layer, n: int) -> void {
     if l.ck_off != null { free(l.ck_off);  free(l.ck_cnt) }
     l.ck_off = words(n * n);  l.ck_cnt = words(n * n)
   }
+  if l.lc_rec == null { l.lc_rec = floats(INST_FLOATS) }
   for i in 0 .. n * n { l.ck_off[i] = -1;  l.ck_cnt[i] = 0 }
   l.count = 0
   layer_chunks_changed(l)
 }
 
-# chunk `id`'s records put into the layer (replacing what it had); as many as the layer has room for
-export function layer_chunk_put(l: Layer, id: int, recs: pointer, count: int, size: float, x0: float, z0: float, y_base: float, lo: float, hi: float) -> void {
+# chunk `id`'s `count` records (format fmt, place_rec.ludic) at byte `at` of recs put into the layer,
+# replacing what it had; as many as the layer has room for
+export function layer_chunk_put(l: Layer, id: int, recs: []byte, at: int, fmt: int, count: int, size: float, x0: float, z0: float, y_base: float, lo: float, hi: float) -> void {
   if l.ck_off == null or id < 0 or id >= len(l.ck_off) { return }
   if l.ck_off[id] >= 0 { layer_chunk_drop(l, id) }
   let n = min(count, l.cap - l.count)
   if n <= 0 { return }
   layer_room(l, l.count + n)
-  let span = size / 65536.0
-  let sr = (hi - lo) / 255.0
   for i in 0 .. n {
-    let r = i * LC_REC
-    let o = (l.count + i) * INST_FLOATS
-    let yaw = float(recs[r + 7]) * (2.0 * PI / 256.0)
-    l.inst[o] = x0 + float(recs[r] | (recs[r + 1] << 8)) * span
-    l.inst[o + 1] = y_base + float(recs[r + 4] | (recs[r + 5] << 8)) * 0.01
-    l.inst[o + 2] = z0 + float(recs[r + 2] | (recs[r + 3] << 8)) * span
-    l.inst[o + 3] = lo + float(recs[r + 6]) * sr
-    l.inst[o + 4] = Math.sin(yaw);  l.inst[o + 5] = Math.cos(yaw)
-    l.inst[o + 6] = float(recs[r + 8]) / 255.0;  l.inst[o + 7] = float(recs[r + 9]) / 255.0
+    prec_get(fmt, recs, at, i, x0, z0, size, y_base, lo, hi, l.lc_rec)
+    for k in 0 .. INST_FLOATS { l.inst[(l.count + i) * INST_FLOATS + k] = l.lc_rec[k] }
   }
   l.ck_off[id] = l.count
   l.ck_cnt[id] = n

packages/ludic.render3d/place_rec.ludic

@@ -0,0 +1,68 @@
+# place_rec.ludic — a baked placement's record, the ONE encoder and decoder the bake, the ring, the
+# physics and the renderer all use (so they cannot drift). Two formats: FULL, 12 bytes, for the fixed
+# kinds (trees, boulders, stones); PACKED, 7 bytes, for the stream kinds (grass, flowers, willow). An
+# encode takes the cell a value falls in and a decode its centre, so decoding and encoding again is
+# stable. A record is read from a []byte at a byte offset (the game cannot index a pointer).
+
+export const PREC_FULL: int = 0
+export const PREC_PACKED: int = 1
+
+export function prec_size(fmt: int) -> int {
+  if fmt == PREC_PACKED { return 7 }
+  return 12
+}
+
+function prec_q(v: float, steps: int) -> int { return min(max(int(Math.floor(v * float(steps))), 0), steps - 1) }
+function prec_r(v: float, top: int) -> int { return min(max(int(Math.floor(v * float(top) + 0.5)), 0), top) }
+function prec_wrap(yaw: float) -> float {
+  let t = 2.0 * PI
+  return yaw - Math.floor(yaw / t) * t
+}
+
+# one instance in world units into b at byte `at`, against its chunk (x0, z0, size, y_base) and kind (lo, hi)
+export function prec_put(fmt: int, b: []byte, at: int, x: float, y: float, z: float, scale: float, yaw: float, seed: float, wind: float, x0: float, z0: float, size: float, y_base: float, lo: float, hi: float) -> void {
+  var sn = 0.0
+  if hi > lo { sn = (scale - lo) / (hi - lo) }
+  if fmt == PREC_PACKED {
+    let qx = prec_q((x - x0) / size, 4096)
+    let qz = prec_q((z - z0) / size, 4096)
+    let qy = min(max(int(Math.floor((y - y_base) * 100.0 + 0.5)), 0), 4095)
+    let lw = qx | (qz << 12) | ((qy & 255) << 24)
+    let hw = ((qy >> 8) & 15) | (prec_r(sn, 63) << 4) | ((prec_r(prec_wrap(yaw) / (2.0 * PI), 64) & 63) << 10) | (prec_r(seed, 15) << 16) | (prec_r(wind, 15) << 20)
+    b[at] = lw & 255;  b[at + 1] = (lw >> 8) & 255;  b[at + 2] = (lw >> 16) & 255;  b[at + 3] = (lw >> 24) & 255
+    b[at + 4] = hw & 255;  b[at + 5] = (hw >> 8) & 255;  b[at + 6] = (hw >> 16) & 255
+    return
+  }
+  let qx = prec_q((x - x0) / size, 65536)
+  let qz = prec_q((z - z0) / size, 65536)
+  let qy = min(max(int(Math.floor((y - y_base) * 100.0 + 0.5)), 0), 65535)
+  b[at] = qx & 255;  b[at + 1] = qx >> 8;  b[at + 2] = qz & 255;  b[at + 3] = qz >> 8
+  b[at + 4] = qy & 255;  b[at + 5] = qy >> 8
+  b[at + 6] = prec_r(sn, 255);  b[at + 7] = prec_r(prec_wrap(yaw) / (2.0 * PI), 256) & 255
+  b[at + 8] = prec_r(seed, 255);  b[at + 9] = prec_r(wind, 255);  b[at + 10] = 0;  b[at + 11] = 0
+}
+
+# record i of the run at byte `at` into out[0 .. 8], the layers' instance layout:
+# x, y, z, scale, sin yaw, cos yaw, seed, wind
+export function prec_get(fmt: int, b: []byte, at: int, i: int, x0: float, z0: float, size: float, y_base: float, lo: float, hi: float, out: floats) -> void {
+  let o = at + i * prec_size(fmt)
+  var qx = 0;  var qz = 0;  var qy = 0;  var qs = 0;  var qa = 0;  var qe = 0;  var qw = 0
+  var xs = 65536.0;  var ss = 255.0;  var as = 256.0;  var es = 255.0
+  if fmt == PREC_PACKED {
+    let lw = b[o] | (b[o + 1] << 8) | (b[o + 2] << 16) | (b[o + 3] << 24)
+    let hw = b[o + 4] | (b[o + 5] << 8) | (b[o + 6] << 16)
+    qx = lw & 4095;  qz = (lw >> 12) & 4095;  qy = ((lw >> 24) & 255) | ((hw & 15) << 8)
+    qs = (hw >> 4) & 63;  qa = (hw >> 10) & 63;  qe = (hw >> 16) & 15;  qw = (hw >> 20) & 15
+    xs = 4096.0;  ss = 63.0;  as = 64.0;  es = 15.0
+  } else {
+    qx = b[o] | (b[o + 1] << 8);  qz = b[o + 2] | (b[o + 3] << 8);  qy = b[o + 4] | (b[o + 5] << 8)
+    qs = b[o + 6];  qa = b[o + 7];  qe = b[o + 8];  qw = b[o + 9]
+  }
+  let yaw = float(qa) / as * 2.0 * PI
+  out[0] = x0 + (float(qx) + 0.5) * size / xs
+  out[1] = y_base + float(qy) * 0.01
+  out[2] = z0 + (float(qz) + 0.5) * size / xs
+  out[3] = lo + float(qs) / ss * (hi - lo)
+  out[4] = Math.sin(yaw);  out[5] = Math.cos(yaw)
+  out[6] = float(qe) / es;  out[7] = float(qw) / es
+}

packages/ludic.render3d/r3d.ludic

@@ -48,6 +48,7 @@ import "layer_chunks.ludic"
 import "fog_impostors.ludic"
 import "actor.ludic"
 import "stream.ludic"
+import "place_rec.ludic"
 import "stream_baked.ludic"
 import "fog_streams.ludic"
 import "grass.ludic"

packages/ludic.render3d/scatter.ludic

@@ -41,6 +41,7 @@ property Layer {
   fog_src:  int = -1,
   ck_off:   words,             # per baked chunk: where its slab starts in inst, or -1 (layer_chunks.ludic)
   ck_cnt:   words,
+  lc_rec:   floats,            # one decoded record, reused
   fog_all:  bool = false,  # the wall keeps (nearly) all of it: casters from sh_buf, no rebuild
   fog_wall: float = 0.0,
   fog_x:    float = 0.0,

packages/ludic.render3d/stream_baked.ludic

@@ -1,7 +1,7 @@
 # stream_baked.ludic — a stream filled from baked chunks instead of generated ones (plan 26 of
 # maroon-lake). The bake stores every instance of a kind once per 64 m chunk, at full density and in a
 # shuffled order, so a distance band draws a PREFIX of it: a nearer band holds everything a farther one
-# does. The stream kinds' records are 7 bytes (below); the fixed layers' 12 (layer_chunks.ludic).
+# does. A record's layout is place_rec.ludic's.
 
 # the stream's cells laid on the baked chunks' grid: `size` metres from the corner (ox, oz)
 export function stream_set_grid(s: Stream, ox: float, oz: float) -> void {
@@ -9,46 +9,13 @@ export function stream_set_grid(s: Stream, ox: float, oz: float) -> void {
   s.oz = oz
 }
 
-# ---- the stream kinds' 7-byte record (the one pack and unpack both the bake and the game use) ----
-# 56 bits, least significant first, bytes little-endian: x 12 (1/4096 of the chunk), z 12, y 12 (over
-# the chunk's y span: y_base + v / 4095 * y_span), scale 6 (lo + v / 63 * (hi - lo)), yaw 6 (v / 64 of a
-# turn), seed 4 (v / 15), wind 4 (v / 15). Read as a low word (bytes 0-3) and a high one (4-6), so no
-# field needs a 64-bit int.
-const SB7_REC: int = 7
-
-# one record's fields (already quantized) written at `at` in `out`
-export function sb7_pack(out: []byte, at: int, x: int, z: int, y: int, scale: int, yaw: int, seed: int, wind: int) -> void {
-  let lo = (x & 4095) | ((z & 4095) << 12) | ((y & 255) << 24)
-  let hi = ((y >> 8) & 15) | ((scale & 63) << 4) | ((yaw & 63) << 10) | ((seed & 15) << 16) | ((wind & 15) << 20)
-  out[at] = lo & 255;  out[at + 1] = (lo >> 8) & 255;  out[at + 2] = (lo >> 16) & 255;  out[at + 3] = (lo >> 24) & 255
-  out[at + 4] = hi & 255;  out[at + 5] = (hi >> 8) & 255;  out[at + 6] = (hi >> 16) & 255
-}
-
-# field k of the record at `at` (0 x, 1 z, 2 y, 3 scale, 4 yaw, 5 seed, 6 wind), as its integer
-export function sb7_field(recs: pointer, at: int, k: int) -> int {
-  let lo = recs[at] | (recs[at + 1] << 8) | (recs[at + 2] << 16) | ((recs[at + 3] & 255) << 24)
-  let hi = recs[at + 4] | (recs[at + 5] << 8) | (recs[at + 6] << 16)
-  if k == 0 { return lo & 4095 }
-  if k == 1 { return (lo >> 12) & 4095 }
-  if k == 2 { return ((lo >> 24) & 255) | ((hi & 15) << 8) }
-  if k == 3 { return (hi >> 4) & 63 }
-  if k == 4 { return (hi >> 10) & 63 }
-  if k == 5 { return (hi >> 16) & 15 }
-  return (hi >> 20) & 15
-}
-
-# the first `keep` 7-byte records of a stream kind's chunk emitted into the chunk being filled
-export function stream_emit_baked(render3d_st: mut Render3dState, s: Stream, recs: pointer, count: int, keep: int, x0: float, z0: float, y_base: float, y_span: float, lo: float, hi: float) -> void {
-  let n = min(keep, count)
-  let span = s.size / 4096.0
-  for i in 0 .. n {
-    let o = i * SB7_REC
-    let x = x0 + float(sb7_field(recs, o, 0)) * span
-    let z = z0 + float(sb7_field(recs, o, 1)) * span
-    let y = y_base + float(sb7_field(recs, o, 2)) / 4095.0 * y_span
-    let scale = lo + float(sb7_field(recs, o, 3)) / 63.0 * (hi - lo)
-    let yaw = float(sb7_field(recs, o, 4)) * (2.0 * PI / 64.0)
-    stream_emit(render3d_st, s, x, y, z, scale, yaw, float(sb7_field(recs, o, 5)) / 15.0, float(sb7_field(recs, o, 6)) / 15.0)
+# the first `keep` of a chunk's `count` records (format fmt, place_rec.ludic) at byte `at` of recs
+# emitted into the chunk being filled
+export function stream_emit_baked(render3d_st: mut Render3dState, s: Stream, recs: []byte, at: int, fmt: int, count: int, keep: int, x0: float, z0: float, y_base: float, lo: float, hi: float) -> void {
+  let v = render3d_st.sb_rec
+  for i in 0 .. min(keep, count) {
+    prec_get(fmt, recs, at, i, x0, z0, s.size, y_base, lo, hi, v)
+    stream_emit(render3d_st, s, v[0], v[1], v[2], v[3], Math.atan2(v[4], v[5]), v[6], v[7])
   }
 }