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Export 3MF with B-rep face tags (#834)

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3MF export carries each triangle's B-rep face tag.
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Irakli Kourtis authored and GitHub committed 2026-10-13 16:29:09 -04:00
1 parent ff7a347013
commit 5d661fa2af
10 files changed
+286 -47
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crates/io/src/threemf.rs
+58 -19
View File
@@ -2,7 +2,10 @@
//! `[Content_Types].xml`, `_rels/.rels` and the model part `3D/3dmodel.model`.
//!
//! Writing: one mesh object per body (shared vertices, outward winding), named after the body,
//! one build item each, colours as base materials. Reading: every build item becomes one mesh
//! one build item each, colours as base materials. Objects with face tags also carry, per
//! triangle, the B-rep face it lies on (`ft:face`, SolidCraft's face-tag namespace; spec:
//! docs/formats/3mf-face-tags.md) and are written at full `f64`
//! precision so the receiver gets the tessellation exactly. Reading: every build item becomes one mesh
//! (components flattened with their transforms), converted to millimetres. Packages are
//! untrusted: sizes, entry counts, mesh sizes and component nesting are capped.
@@ -28,6 +31,9 @@ const MAX_XML_DEPTH: usize = 256;
const CORE_NS: &str = "http://schemas.microsoft.com/3dmanufacturing/core/2015/02";
const MODEL_REL: &str = "http://schemas.microsoft.com/3dmanufacturing/2013/01/3dmodel";
/// SolidCraft's face-tag namespace, version 1: `ft:face` on triangles, `ft:faces` on objects
/// (docs/formats/3mf-face-tags.md).
pub const FACE_TAGS_NS: &str = "https://github.com/bherbruck/solidcraft/formats/3mf-face-tags/2026/10";
/// A named triangle mesh (millimetres, counter-clockwise seen from outside).
#[derive(Clone, Debug, Default, PartialEq)]
@@ -43,6 +49,17 @@ pub struct MeshObject {
/// empty when no triangle has one.
pub looks: Vec<([f32; 3], f32)>,
pub tri_looks: Vec<u32>,
/// The B-rep face each triangle lies on, or empty for no face tags. A tagged object is
/// written with exact (`f64`) coordinates.
pub tri_faces: Vec<u32>,
/// Number of B-rep faces (written as `ft:faces` when the object is tagged).
pub faces: u32,
}
impl MeshObject {
fn tagged(&self) -> bool {
!self.tri_faces.is_empty()
}
}
fn esc(s: &str) -> String {
@@ -61,14 +78,24 @@ fn esc(s: &str) -> String {
o
}
/// Shared vertices (merged at single precision, as written) and non-degenerate triangles.
fn indexed(m: &MeshObject) -> (Vec<[f32; 3]>, Vec<([u32; 3], u32)>) {
let mut map: HashMap<[u32; 3], u32> = HashMap::new();
let mut verts: Vec<[f32; 3]> = Vec::new();
/// A triangle as written: its vertices, its colour entry (0: the object's own) and its face.
struct Tri {
v: [u32; 3],
look: u32,
face: u32,
}
/// Shared vertices, merged at the precision they are written in (single, or double for tagged
/// objects), and non-degenerate triangles.
fn indexed(m: &MeshObject) -> (Vec<[f64; 3]>, Vec<Tri>) {
let exact = m.tagged();
let mut map: HashMap<[u64; 3], u32> = HashMap::new();
let mut verts: Vec<[f64; 3]> = Vec::new();
let mut remap = Vec::with_capacity(m.positions.len());
for p in &m.positions {
let v = [p.x as f32 + 0.0, p.y as f32 + 0.0, p.z as f32 + 0.0];
let key = v.map(f32::to_bits);
// `+ 0.0` turns -0 into 0, so both merge.
let v = if exact { [p.x + 0.0, p.y + 0.0, p.z + 0.0] } else { [p.x as f32 as f64 + 0.0, p.y as f32 as f64 + 0.0, p.z as f32 as f64 + 0.0] };
let key = v.map(f64::to_bits);
let next = u32::try_from(verts.len()).unwrap_or(u32::MAX);
let i = *map.entry(key).or_insert_with(|| {
verts.push(v);
@@ -82,7 +109,11 @@ fn indexed(m: &MeshObject) -> (Vec<[f32; 3]>, Vec<([u32; 3], u32)>) {
.enumerate()
.filter_map(|(k, t)| {
let (a, b, c) = (*remap.get(t[0] as usize)?, *remap.get(t[1] as usize)?, *remap.get(t[2] as usize)?);
(a != b && b != c && c != a).then_some(([a, b, c], m.tri_looks.get(k).copied().unwrap_or(0)))
(a != b && b != c && c != a).then(|| Tri {
v: [a, b, c],
look: m.tri_looks.get(k).copied().unwrap_or(0),
face: m.tri_faces.get(k).copied().unwrap_or(0),
})
})
.collect();
(verts, tris)
@@ -210,7 +241,8 @@ pub fn weld_tagged(positions: &[Vec3], triangles: &[[u32; 3]], tags: &[u32], eps
pub fn model_xml(objects: &[MeshObject]) -> String {
let mut x = String::new();
x.push_str("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
let _ = writeln!(x, "<model unit=\"millimeter\" xml:lang=\"en-US\" xmlns=\"{CORE_NS}\">");
let ft = if objects.iter().any(MeshObject::tagged) { format!(" xmlns:ft=\"{FACE_TAGS_NS}\"") } else { String::new() };
let _ = writeln!(x, "<model unit=\"millimeter\" xml:lang=\"en-US\" xmlns=\"{CORE_NS}\"{ft}>");
x.push_str(" <metadata name=\"Application\">SolidCraft</metadata>\n <resources>\n");
let colored = objects.iter().any(|o| o.color.is_some() || o.transparency > 0.0 || !o.looks.is_empty());
// Base material group id 1 (each object's own colour, then its faces' colours); objects
@@ -240,22 +272,29 @@ pub fn model_xml(objects: &[MeshObject]) -> String {
let id = k + 2;
let own = first.get(k).copied().unwrap_or(0);
let mat = if colored { format!(" pid=\"1\" pindex=\"{own}\"") } else { String::new() };
let _ = writeln!(x, " <object id=\"{id}\" type=\"model\" name=\"{}\"{mat}>", esc(&o.name));
let faces = if o.tagged() { format!(" ft:faces=\"{}\"", o.faces.max(1)) } else { String::new() };
let _ = writeln!(x, " <object id=\"{id}\" type=\"model\" name=\"{}\"{mat}{faces}>", esc(&o.name));
x.push_str(" <mesh>\n <vertices>\n");
let (verts, tris) = indexed(o);
for v in &verts {
let _ = writeln!(x, " <vertex x=\"{}\" y=\"{}\" z=\"{}\"/>", v[0], v[1], v[2]);
// Shortest round-trip form: f64 comes back exactly, f32 as written before.
if o.tagged() {
let _ = writeln!(x, " <vertex x=\"{}\" y=\"{}\" z=\"{}\"/>", v[0], v[1], v[2]);
} else {
let _ = writeln!(x, " <vertex x=\"{}\" y=\"{}\" z=\"{}\"/>", v[0] as f32, v[1] as f32, v[2] as f32);
}
}
x.push_str(" </vertices>\n <triangles>\n");
for (t, look) in &tris {
match look {
l if colored && *l > 0 && (*l as usize) <= o.looks.len() => {
let _ = writeln!(x, " <triangle v1=\"{}\" v2=\"{}\" v3=\"{}\" pid=\"1\" p1=\"{}\"/>", t[0], t[1], t[2], own + *l as usize);
}
_ => {
let _ = writeln!(x, " <triangle v1=\"{}\" v2=\"{}\" v3=\"{}\"/>", t[0], t[1], t[2]);
}
for t in &tris {
let [a, b, c] = t.v;
let _ = write!(x, " <triangle v1=\"{a}\" v2=\"{b}\" v3=\"{c}\"");
if colored && t.look > 0 && (t.look as usize) <= o.looks.len() {
let _ = write!(x, " pid=\"1\" p1=\"{}\"", own + t.look as usize);
}
if o.tagged() {
let _ = write!(x, " ft:face=\"{}\"", t.face);
}
x.push_str("/>\n");
}
x.push_str(" </triangles>\n </mesh>\n </object>\n");
}