src/engine/models-world-loader.js

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/* ============================================================================
   WORLD MODEL LOADER
   ----------------------------------------------------------------------------
   Turns the compact WORLD_MODELS table into InstMesh-ready geometry.  Kept
   separate from the data file so the data file can be regenerated without
   touching runtime logic.
   ============================================================================ */
function loadWorldModel(name,authoredUV){
  const D=WORLD_MODELS[name];
  if(!D){ console.warn('world model not found:',name); return null; }
  const vc=D.vertexCount, ic=D.indexCount;
  const uvSrc=authoredUV&&D.uv2?D.uv2:D.uv;
  /* Curated scenery owns a contact plane. Normalising it here means a Blender
     export with its pivot at world origin cannot hover above (or disappear
     below) terrain. Existing assets have contactY=0, so old saves do not move. */
  const contactY=Number.isFinite(D.contactY)?D.contactY:0;
  const v=new Float32Array(vc*12);
  for(let i=0;i<vc;i++){
    const o=i*12;
    const p=i*3, u=i*2;
    v[o  ]=D.pos[p  ]; v[o+1]=D.pos[p+1]-contactY; v[o+2]=D.pos[p+2]; // grounded position
    v[o+3]=D.nrm[p  ]; v[o+4]=D.nrm[p+1]; v[o+5]=D.nrm[p+2];   // normal
    v[o+6]=1;          v[o+7]=1;          v[o+8]=1;            // colour (white, atlas multiplies)
    v[o+9]=uvSrc[u];    v[o+10]=uvSrc[u+1];                    // legacy tiled or authored UV0
    v[o+11]=D.mat[i];
  }
  const iArr=new Uint16Array(ic);
  for(let k=0;k<ic;k++) iArr[k]=D.idx[k];
  /* Hall pitches sit at ny~0.36–0.41, so |ny|>0.45 left CONC panes on the
     roof. Chimney CAPS are RUST/LAMP (+Y quads span<12) — rust + the
     industrial amber fill reads as a glowing disc. Windows only on
     near-vertical walls. A tessellated dome roof is also many small +Y
     tris: treating each as a chimney, then painting an 80-unit TRIM
     cylinder under it, turned the whole bowl into unlit metal (solid
     black). Cluster first; only an isolated island is a stack. */
  if(typeof MAT!=='undefined'&&D.idx&&D.pos&&D.nrm){
    const roofId=MAT.ROOF+1, trimId=MAT.TRIM+1, litId=MAT.BUILD_OFFICE_LIT+1;
    const ymax=D.bounds?D.bounds[1][1]:0;
    const bx0=D.bounds?D.bounds[0][0]:-50, bx1=D.bounds?D.bounds[1][0]:50;
    const bz0=D.bounds?D.bounds[0][2]:-50, bz1=D.bounds?D.bounds[1][2]:50;
    const meshXZ=Math.hypot(bx1-bx0, bz1-bz0);
    const seeds=[];
    for(let t=0;t<ic;t+=3){
      const a=iArr[t],b=iArr[t+1],c=iArr[t+2];
      const ny=(D.nrm[a*3+1]+D.nrm[b*3+1]+D.nrm[c*3+1])/3;
      if(ny<0.70)continue;
      const x=(D.pos[a*3]+D.pos[b*3]+D.pos[c*3])/3;
      const y=(D.pos[a*3+1]+D.pos[b*3+1]+D.pos[c*3+1])/3;
      const z=(D.pos[a*3+2]+D.pos[b*3+2]+D.pos[c*3+2])/3;
      const x0=Math.min(D.pos[a*3],D.pos[b*3],D.pos[c*3]), x1=Math.max(D.pos[a*3],D.pos[b*3],D.pos[c*3]);
      const z0=Math.min(D.pos[a*3+2],D.pos[b*3+2],D.pos[c*3+2]), z1=Math.max(D.pos[a*3+2],D.pos[b*3+2],D.pos[c*3+2]);
      const span=Math.hypot(x1-x0,z1-z0);
      if(span<12&&y>ymax*0.28) seeds.push({x,y,z,span});
    }
    const nS=seeds.length, par=new Int32Array(nS);
    for(let i=0;i<nS;i++) par[i]=i;
    const find=i=>{ while(par[i]!==i) i=par[i]=par[par[i]]; return i; };
    for(let i=0;i<nS;i++) for(let j=i+1;j<nS;j++){
      const A=seeds[i],B=seeds[j];
      if(Math.abs(A.y-B.y)<10&&Math.hypot(A.x-B.x,A.z-B.z)<14){
        const ai=find(i),aj=find(j); if(ai!==aj) par[ai]=aj;
      }
    }
    const groups=new Map();
    for(let i=0;i<nS;i++){
      const r=find(i), S=seeds[i];
      let G=groups.get(r);
      if(!G){ G={n:0,x0:1e9,x1:-1e9,z0:1e9,z1:-1e9,y:0,sx:0,sz:0}; groups.set(r,G); }
      G.n++; G.y+=S.y; G.sx+=S.x; G.sz+=S.z;
      G.x0=Math.min(G.x0,S.x-S.span*0.5); G.x1=Math.max(G.x1,S.x+S.span*0.5);
      G.z0=Math.min(G.z0,S.z-S.span*0.5); G.z1=Math.max(G.z1,S.z+S.span*0.5);
    }
    const caps=[], spanLim=Math.min(9, meshXZ*0.20);
    groups.forEach(G=>{
      const span=Math.hypot(G.x1-G.x0, G.z1-G.z0);
      if(span<spanLim&&G.n<24)
        caps.push({x:G.sx/G.n, y:G.y/G.n, z:G.sz/G.n, r:Math.max(4,span*0.55)});
    });
    /* Tight column under a real stack. Not an 80-unit cylinder — that ate
       every dome whose peak happened to be one small +Y triangle. */
    const nearCap=(x,y,z)=>{
      for(let k=0;k<caps.length;k++){
        const C=caps[k];
        if(y>C.y-50&&y<C.y+4&&Math.hypot(x-C.x,z-C.z)<C.r+3) return true;
      }
      return false;
    };
    const winRaw=raw=>raw===MAT.CONC||raw===MAT.BUILD||raw===MAT.GREEBLE||raw===MAT.LAMP
      ||raw===MAT.BUILD_OFFICE_LIT||raw===MAT.BUILD_OFFICE_COOL||raw===MAT.BUILD_NIGHT_FLICKER
      ||raw===MAT.PRECAST_BAY||raw===MAT.NEON_FACADE;
    const uvS=typeof UVS==='number'?UVS:0.055;
    for(let i=0;i<vc;i++){
      const o=i*12;
      const nx=v[o+3], ny=v[o+4], nz=v[o+5];
      const ax=Math.abs(nx), ay=Math.abs(ny), az=Math.abs(nz);
      const facade=ay<0.22&&Math.max(ax,az)>0.85;
      const mid=v[o+11];
      const sgn=mid<0?-1:1;
      const raw=(Math.floor(Math.abs(mid))-1)|0;
      const capVert=nearCap(v[o],v[o+1],v[o+2]);
      /* Civic louvres used to stay MAT.LAMP. That tile was a radial
         orange blob, so a vertical pane read as a fat orb from the
         command camera. Cool office glass keeps the slat and the light. */
      if(capVert&&!(facade&&raw===MAT.LAMP&&ny<=0.55)){
        if(ny>0.45) v[o+11]=roofId*sgn;
        else if(winRaw(raw)||raw===MAT.RUST||raw===MAT.TRIM) v[o+11]=trimId*sgn;
      }else if(!facade&&(winRaw(raw)||((raw===MAT.RUST||raw===MAT.LAMP)&&ny>0.45))){
        v[o+11]=roofId*sgn;                   // pitches, ridges, decks, interiors
      }else if(facade&&raw===MAT.LAMP){
        v[o+11]=(MAT.BUILD_OFFICE_COOL+1)*sgn;
      }else if(facade&&(raw===MAT.CONC||raw===MAT.BUILD)){
        v[o+11]=litId*sgn;                    // readable window band on walls
      }
      /* Tiny authored UV islands on a tessellated crown NaN the cotangent
         frame and shade black. XZ planar UVs keep ROOF/TRIM sampling.
         0.35 covers hall pitches (ny~0.36) the 0.45 gate missed. */
      if(ay>0.35){
        const fin=(Math.floor(Math.abs(v[o+11]))-1)|0;
        if(fin===MAT.ROOF||fin===MAT.TRIM){ v[o+9]=v[o]*uvS; v[o+10]=v[o+2]*uvS; }
      }
    }
  }
  return {v:v, i:iArr, count:ic, bones:0,
    bounds:D.bounds||null,contactY:0,sourceContactY:contactY,
    uvMode:authoredUV&&D.uv2?'authored':(D.uvMode||'legacy')};
}