`nx_stl_write.nx` source

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1// nx_stl_write.nx -- SOVEREIGN DCC export: procedural mesh -> binary STL.
2//
3// The creator/writer half (nx_stl is the reader).  Emits the exact 1980s binary
4// STL the existing slicer->gcode->klipper pipeline consumes: 80B header + u32
5// n_tris + per-tri 50B (12B normal + 9 f32 verts + 2B attr).  Floats via the new
6// f32_from_i64 encoder; bytes via nx_le_write_u32.  This is the model->print seam:
7// geometry authored here feeds nx_stl_load_binary -> nx_slice_* -> nx_gcode_* ->
8// nx_klipper_gcode_validator.  No dup (nx_stl had no writer).  license_tier: ORIGINAL.
9
10import "nx_syscalls.nx"
11import "nx_le.nx"
12import "nx_f32_encode.nx"
13import "nx_mesh.nx"
14
15// write one vertex (x,y,z mm) as 3 little-endian f32 at off; returns off+12
16func sw_put_vert(buf: *u8, off: i64, x: i64, y: i64, z: i64) -> i64 {
17    nx_le_write_u32(buf, off, f32_from_i64(x))
18    nx_le_write_u32(buf, off + 4, f32_from_i64(y))
19    nx_le_write_u32(buf, off + 8, f32_from_i64(z))
20    return off + 12
21}
22
23// write a binary STL of a cube of side S (mm) into buf; returns total bytes (684)
24func nx_stl_write_cube(buf: *u8, S: i64) -> i64 {
25    let cx: *i64 = (sys_mmap(8 * 8)) as *i64
26    let cy: *i64 = (sys_mmap(8 * 8)) as *i64
27    let cz: *i64 = (sys_mmap(8 * 8)) as *i64
28    cx[0] = 0; cy[0] = 0; cz[0] = 0
29    cx[1] = S; cy[1] = 0; cz[1] = 0
30    cx[2] = S; cy[2] = S; cz[2] = 0
31    cx[3] = 0; cy[3] = S; cz[3] = 0
32    cx[4] = 0; cy[4] = 0; cz[4] = S
33    cx[5] = S; cy[5] = 0; cz[5] = S
34    cx[6] = S; cy[6] = S; cz[6] = S
35    cx[7] = 0; cy[7] = S; cz[7] = S
36    let ta: *i64 = (sys_mmap(12 * 8)) as *i64
37    let tb: *i64 = (sys_mmap(12 * 8)) as *i64
38    let tc: *i64 = (sys_mmap(12 * 8)) as *i64
39    ta[0]=0;tb[0]=1;tc[0]=2;   ta[1]=0;tb[1]=2;tc[1]=3
40    ta[2]=5;tb[2]=4;tc[2]=7;   ta[3]=5;tb[3]=7;tc[3]=6
41    ta[4]=4;tb[4]=0;tc[4]=3;   ta[5]=4;tb[5]=3;tc[5]=7
42    ta[6]=1;tb[6]=5;tc[6]=6;   ta[7]=1;tb[7]=6;tc[7]=2
43    ta[8]=4;tb[8]=5;tc[8]=1;   ta[9]=4;tb[9]=1;tc[9]=0
44    ta[10]=3;tb[10]=2;tc[10]=6; ta[11]=3;tb[11]=6;tc[11]=7
45
46    var i: i64 = 0
47    while i < 80 { buf[i] = 0 as u8; i = i + 1 }     // 80-byte header (ignored)
48    nx_le_write_u32(buf, 80, 12)                      // n_tris
49    var off: i64 = 84
50    var t: i64 = 0
51    while t < 12 {
52        nx_le_write_u32(buf, off, 0)                  // normal = (0,0,0) f32 (reader ignores)
53        nx_le_write_u32(buf, off + 4, 0)
54        nx_le_write_u32(buf, off + 8, 0)
55        off = off + 12
56        let a: i64 = ta[t]; let b: i64 = tb[t]; let c: i64 = tc[t]
57        off = sw_put_vert(buf, off, cx[a], cy[a], cz[a])
58        off = sw_put_vert(buf, off, cx[b], cy[b], cz[b])
59        off = sw_put_vert(buf, off, cx[c], cy[c], cz[c])
60        nx_le_write_u16(buf, off, 0)                  // attribute byte count
61        off = off + 2
62        t = t + 1
63    }
64    return off
65}
66
67// ===== GENERAL mesh export: ANY NxMesh -> binary STL =================
68//
69// The cube-only writer above proved the seam; this writes an ARBITRARY
70// authored mesh (the output of the DCC editor / CAD kernel) to the exact
71// binary STL the slicer consumes.  Vertices are read from the mesh in its
72// native Q14-mm units and encoded with f32_from_q14 (exact), so sub-mm
73// geometry survives.  Triangle corners are emitted unindexed (STL has no
74// shared-vertex table); the existing nx_stl_load_binary re-dedups them on
75// read.  buf must hold >= 84 + 50*m.n_tris bytes.  Returns bytes written.
76
77// write vertex `vidx` of mesh `m` (Q14 mm) as 3 little-endian f32; off+12
78func sw_put_mesh_vert(buf: *u8, off: i64, m: *NxMesh, vidx: i64) -> i64 {
79    nx_le_write_u32(buf, off,     f32_from_q14(nx_mesh_get_vertex_x(m, vidx)))
80    nx_le_write_u32(buf, off + 4, f32_from_q14(nx_mesh_get_vertex_y(m, vidx)))
81    nx_le_write_u32(buf, off + 8, f32_from_q14(nx_mesh_get_vertex_z(m, vidx)))
82    return off + 12
83}
84
85func nx_stl_write_mesh(buf: *u8, m: *NxMesh) -> i64 {
86    var i: i64 = 0
87    while i < 80 { buf[i] = 0 as u8; i = i + 1 }       // 80-byte header (ignored)
88    let nt: i64 = m.n_tris
89    nx_le_write_u32(buf, 80, nt)                       // n_tris
90    var off: i64 = 84
91    var t: i64 = 0
92    while t < nt {
93        nx_le_write_u32(buf, off, 0)                  // normal = (0,0,0) f32 (reader trusts winding)
94        nx_le_write_u32(buf, off + 4, 0)
95        nx_le_write_u32(buf, off + 8, 0)
96        off = off + 12
97        let a: i64 = m.indices[t * 3 + 0]
98        let b: i64 = m.indices[t * 3 + 1]
99        let c: i64 = m.indices[t * 3 + 2]
100        off = sw_put_mesh_vert(buf, off, m, a)
101        off = sw_put_mesh_vert(buf, off, m, b)
102        off = sw_put_mesh_vert(buf, off, m, c)
103        nx_le_write_u16(buf, off, 0)                  // attribute byte count
104        off = off + 2
105        t = t + 1
106    }
107    return off
108}
nx_stl_write.nx source

`nx_stl_write.nx` source
