`nx_gi_path.nx` source

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1// nx_gi_path.nx -- THE BEAUTY TIER'S FIRST BYTE: a sovereign INTEGER PATH TRACER over the procgen heightfield.
2// graphics GR42 (env_beauty_scene) + GR10 (gp_bounce_gi); operator 2026-09-02, looking at /world/beach: "that looks like
3// our junk cpu stuff ... lets get things infinigen generating to photoreal". Infinigen renders offline through a path
4// tracer; this organ is that twin, first byte up: no float, no library, no third party -- the same fx1024 arithmetic,
5// the same fBm heightfield (nx_worldgen wg_terrain_h), the same sky model (wg_sky), the same soft-shadow march
6// (wg_sun_pen) and the same PNG writer the estate already ships. What is NEW is the light transport: every pixel is
7// the mean of spp Monte Carlo paths, each path = primary ray -> Lambertian hit (direct sun x soft shadow) -> cosine-
8// weighted bounce (BRDF x cos / pdf = albedo, so no division noise) -> up to GP_BOUNCES hits -> sky gather when the
9// path escapes. Colour bleed and sky occlusion therefore emerge from transport instead of being painted on, which is
10// the difference between the raymarcher's "ambient = 42" and a beauty tier.
11//
12// DETERMINISM: the sampler is a seeded integer LCG advanced per draw; two runs with the same argv are byte-identical,
13// so a gate can diff frames (the GR10 cache-vs-rebuild law carried into path tracing).
14// NO TERRACING: the march step grows with distance (footprint-sized) and every hit is REFINED by GP_REFINE bisections,
15// so the surface lands within a fraction of a unit -- the stair-steps visible in every nx_worldgen slope are gone.
16// HONEST LIMITS OF THIS FIRST BYTE, stated so the next reader does not credit them: terrain is Lambertian only (no
17// specular, no BRDF model beyond albedo); water is a single mirror event tinted by a deep colour, not refraction;
18// the sky is nx_worldgen's gradient+sun+cloud model, not GR26's Rayleigh/Mie atmosphere; no cast meshes yet; no
19// depth/normal/semantic ground-truth siblings yet (the dataset half of GR42). Each of those is a named rung.
20// UNITS: directions are fx1024 unit vectors; radiance is carried as throughput(fx1024) x colour(0..255), then averaged,
21// Reinhard-mapped and display-encoded ONCE at output (GR14's linear-light law: all transport in linear).
22//
23//   nx_gi_path <out.png> [seed] [spp] [weather 0 clear | 1 sunset | 2 overcast] [yaw 0..4095]
24// exit: 0 written | 2 usage | 5 png-write-fail.  license_tier: ORIGINAL   No hw writes (Rule 26).
25import "nx_syscalls.nx"
26import "nx_gi_path_lib.nx"
27
28// THE BOARD'S CONTRACT SYMBOL (graphics GR10 gp_bounce_gi): one bounce-lit path estimate for a ray. The watch row
29// on /compare/graphics flips when this symbol exists in this organ; the flip is the receipt, the GR42 gate is the proof.
30func gp_bounce_gi(ox: i64, oy: i64, oz: i64, dx: i64, dy: i64, dz: i64, seed: i64, Wp: *i64, st: *i64,
                hitb: *i64, n: *i64, alb: *i64, scr: *i64, dir: *i64, sky: *i64, L: *i64, stats: *i64) -> i64 {
  return gp_trace(ox, oy, oz, dx, dy, dz, seed, Wp, st, hitb, n, alb, scr, dir, sky, L, stats)
33}
34
35func main(argc: i64, argv: *i64) -> i64 {
  let out: *u8 = sys_mmap(GP_OUT)
  if argc < 2 {
      var uo: i64 = gp_cat(out, 0, "usage: nx_gi_path <out.png> [seed] [spp] [weather 0 clear|1 sunset|2 overcast] [yaw 0..4095]   -- sovereign integer path tracer over the procgen heightfield\n" as *u8)
      sys_write(1, out, uo)
      sys_exit(GP_EXIT_USAGE); return GP_EXIT_USAGE
  }
  let path: *u8 = argv[1] as *u8
  var seed: i64 = 77
  if argc >= 3 { seed = gp_atoi(argv[2] as *u8) }
  var spp: i64 = GP_SPP_DEFAULT
  if argc >= 4 { spp = gp_atoi(argv[3] as *u8) }
  if spp < 1 { spp = 1 }
  var mode: i64 = 0
  if argc >= 5 { mode = gp_atoi(argv[4] as *u8) }
  var yaw: i64 = 0
  if argc >= 6 { yaw = gp_atoi(argv[5] as *u8) }
  let gw: i64 = wg_w()*GP_FRAC_NUM/GP_FRAC_DEN
  let gh: i64 = wg_h()*GP_FRAC_NUM/GP_FRAC_DEN
  let focal: i64 = WG_FOCAL*GP_FRAC_NUM/GP_FRAC_DEN
  let horizon: i64 = WG_HORIZON*GP_FRAC_NUM/GP_FRAC_DEN
  let Wp: *i64 = sys_mmap(32*8) as *i64
  wg_weather(mode, Wp)
  let hitb: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let n: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let alb: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let scr: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let dir: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let sky: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let L: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let stats: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let st: *i64 = sys_mmap(GP_WORDS*8) as *i64
  let d: *i64 = sys_mmap(GP_WORDS*8) as *i64
  st[0] = seed*GP_LCG_A + GP_LCG_C
  let acc: *i64 = sys_mmap(gw*gh*3*8) as *i64
  let rgb: *u8 = sys_mmap(gw*gh*3 + 16)
  let t0: i64 = sys_now_ms()
  let camx: i64 = 0
  let camy: i64 = wg_cam_base_y(seed)
  let camz: i64 = 0
  let sy4: i64 = it_sin4096(yaw)
  let cy4: i64 = it_cos4096(yaw)
  var py: i64 = 0
  while py < gh {
      var px: i64 = 0
      while px < gw {
          let pi: i64 = (py*gw + px)*3
          var s: i64 = 0
          while s < spp {
              let jx: i64 = gp_rnd(st)
              let jy: i64 = gp_rnd(st)
              let sxo: i64 = (px - gw/2)*GP_FX + jx - GP_HALF
              let syo: i64 = ((gh/2 - py) - horizon)*GP_FX + jy - GP_HALF
              d[0] = focal*GP_FX*sy4/GP_CIRCLE + sxo*cy4/GP_CIRCLE
              d[1] = syo
              d[2] = focal*GP_FX*cy4/GP_CIRCLE - sxo*sy4/GP_CIRCLE
              gp_norm3(d)
              gp_bounce_gi(camx, camy, camz, d[0], d[1], d[2], seed, Wp, st, hitb, n, alb, scr, dir, sky, L, stats)
              acc[pi] = acc[pi] + L[0]
              acc[pi + 1] = acc[pi + 1] + L[1]
              acc[pi + 2] = acc[pi + 2] + L[2]
              s = s + 1
          }
          rgb[pi] = gp_encode(acc[pi]/spp) as u8
          rgb[pi + 1] = gp_encode(acc[pi + 1]/spp) as u8
          rgb[pi + 2] = gp_encode(acc[pi + 2]/spp) as u8
          px = px + 1
      }
      py = py + 1
  }
  let ms: i64 = sys_now_ms() - t0
  let wrc: i64 = nx_png_write_rgb(path, rgb, gw, gh)
  var o: i64 = gp_cat(out, 0, "GI-PATH w=" as *u8); o = gp_num(out, o, gw)
  o = gp_cat(out, o, " h=" as *u8); o = gp_num(out, o, gh)
  o = gp_cat(out, o, " spp=" as *u8); o = gp_num(out, o, spp)
  o = gp_cat(out, o, " bounces=" as *u8); o = gp_num(out, o, GP_BOUNCES)
  o = gp_cat(out, o, " seed=" as *u8); o = gp_num(out, o, seed)
  o = gp_cat(out, o, " weather=" as *u8); o = gp_num(out, o, mode)
  o = gp_cat(out, o, " yaw=" as *u8); o = gp_num(out, o, yaw)
  o = gp_cat(out, o, " marches=" as *u8); o = gp_num(out, o, stats[GP_ST_MARCHES])
  o = gp_cat(out, o, " sky_rays=" as *u8); o = gp_num(out, o, stats[GP_ST_SKY])
  o = gp_cat(out, o, " water_rays=" as *u8); o = gp_num(out, o, stats[GP_ST_WATER])
  o = gp_cat(out, o, " terrain_hits=" as *u8); o = gp_num(out, o, stats[GP_ST_TERRAIN])
  o = gp_cat(out, o, " ms=" as *u8); o = gp_num(out, o, ms)
  o = gp_cat(out, o, " png_rc=" as *u8); o = gp_num(out, o, wrc)
  o = gp_cat(out, o, " wrote=" as *u8); o = gp_cat(out, o, path)
  o = gp_cat(out, o, "\n" as *u8)
  sys_write(1, out, o)
  if wrc < 0 { sys_exit(GP_EXIT_WRITE); return GP_EXIT_WRITE }
  sys_exit(GP_EXIT_OK)
  return GP_EXIT_OK
126}
nx_gi_path.nx source

`nx_gi_path.nx` source
