uvunwrap 0.2.0

Pure-Rust automatic UV unwrapping: chart segmentation, LSCM parameterization and atlas packing (lightmap UVs, baking)
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262

//! Unwraps an OBJ file and writes the result as OBJ (with `vt`) plus an SVG
//! drawing of each atlas page.
//!
//! ```text
//! cargo run --release --example unwrap -- [--fast] [--flat] [--block-align]
//!     [--texels-per-unit X] [--max-chart-size N] [--padding N] [--page-size N]
//!     [--instances 1,2,0.5] [--keep-uvs] [input.obj] [output_prefix]
//! ```
//!
//! Vertices are split per distinct `v/vt/vn` corner, as an engine import
//! would, so UV seams and hard edges reach the unwrapper. `--flat` gives every
//! triangle its own vertices instead (flat shading). Quads and n-gons stay
//! whole: each OBJ face is passed as one polygon. `--keep-uvs` repacks the
//! OBJ's own `vt` islands instead of unwrapping. Without arguments, a
//! built-in torus is unwrapped into `out/torus*`.

mod common;

use std::collections::HashMap;
use std::fmt::Write as _;
use std::time::Instant;
use std::{env, fs};

/// Positions, triangle indices, each triangle's polygon (its `f` line) and
/// (if complete) per-vertex UVs.
type Obj = (Vec<[f32; 3]>, Vec<u32>, Vec<u32>, Option<Vec<[f32; 2]>>);

/// Loads an OBJ with one vertex per distinct `v/vt/vn` corner, plus each
/// vertex's `vt` (if every vertex has one). Quads and n-gons are
/// fan-triangulated, remembering which polygon each triangle came from.
fn load_obj(text: &str) -> Obj {
    let mut v: Vec<[f32; 3]> = Vec::new();
    let mut vt: Vec<[f32; 2]> = Vec::new();
    let mut uvs: Vec<Option<[f32; 2]>> = Vec::new();
    let nn = &mut 0i64;
    let mut corners: HashMap<[i64; 3], u32> = HashMap::new();
    let mut positions = Vec::new();
    let mut indices = Vec::new();
    let mut polygons = Vec::new();
    let mut face_count = 0u32;
    for line in text.lines() {
        let mut it = line.split_whitespace();
        match it.next() {
            Some("v") => {
                let c: Vec<f32> = it.take(3).map(|s| s.parse().unwrap_or(0.0)).collect();
                v.push([c[0], c[1], c[2]]);
            }
            Some("vt") => {
                let c: Vec<f32> = it.take(2).map(|s| s.parse().unwrap_or(0.0)).collect();
                vt.push([c[0], 1.0 - c.get(1).copied().unwrap_or(0.0)]); // OBJ's v points up
            }
            Some("vn") => *nn += 1,
            Some("f") => {
                // "f a/b/c ..." with 1-based or negative indices; fan-triangulate polygons.
                let polygon = face_count;
                face_count += 1;
                let counts = [v.len() as i64, vt.len() as i64, *nn];
                let poly: Vec<u32> = it
                    .filter_map(|t| {
                        let mut key = [-1i64; 3];
                        for (k, part) in t.split('/').take(3).enumerate() {
                            if let Ok(i) = part.parse::<i64>() {
                                key[k] = if i < 0 { counts[k] + i } else { i - 1 };
                            }
                        }
                        let p = *v.get(usize::try_from(key[0]).ok()?)?;
                        let uv = usize::try_from(key[1])
                            .ok()
                            .and_then(|i| vt.get(i).copied());
                        Some(*corners.entry(key).or_insert_with(|| {
                            positions.push(p);
                            uvs.push(uv);
                            (positions.len() - 1) as u32
                        }))
                    })
                    .collect();
                for k in 1..poly.len().saturating_sub(1) {
                    indices.extend([poly[0], poly[k], poly[k + 1]]);
                    polygons.push(polygon);
                }
            }
            _ => {}
        }
    }
    let uvs = uvs
        .into_iter()
        .collect::<Option<Vec<_>>>()
        .filter(|u| !u.is_empty());
    (positions, indices, polygons, uvs)
}

/// Gives every triangle its own three vertices.
fn flatten(positions: &[[f32; 3]], indices: &[u32]) -> (Vec<[f32; 3]>, Vec<u32>) {
    (
        indices.iter().map(|&i| positions[i as usize]).collect(),
        (0..indices.len() as u32).collect(),
    )
}

fn main() {
    let mut opts = uvunwrap::Options::default();
    let mut args: Vec<String> = env::args().skip(1).collect();
    if let Some(i) = args.iter().position(|a| a == "--fast") {
        opts.packing = uvunwrap::Packing::Fast;
        args.remove(i);
    }
    let flat = args
        .iter()
        .position(|a| a == "--flat")
        .map(|i| args.remove(i))
        .is_some();
    let keep_uvs = args
        .iter()
        .position(|a| a == "--keep-uvs")
        .map(|i| args.remove(i))
        .is_some();
    opts.block_align = args
        .iter()
        .position(|a| a == "--block-align")
        .map(|i| args.remove(i))
        .is_some();
    let mut value = |name: &str| {
        let i = args.iter().position(|a| a == name)?;
        args.remove(i);
        Some(args.remove(i))
    };
    let texels_per_unit: Option<f32> =
        value("--texels-per-unit").map(|v| v.parse().expect("--texels-per-unit"));
    if let Some(v) = value("--max-chart-size") {
        opts.max_chart_size = v.parse().expect("--max-chart-size");
    }
    let instances: Vec<f32> = value("--instances")
        .map(|v| {
            v.split(',')
                .map(|k| k.parse().expect("--instances"))
                .collect()
        })
        .unwrap_or_default();
    let page_size: Option<u32> = value("--page-size").map(|v| v.parse().expect("--page-size"));
    opts.density = match texels_per_unit {
        Some(texels_per_unit) => uvunwrap::Density::Fixed {
            texels_per_unit,
            page_size,
        },
        None => uvunwrap::Density::Auto {
            page_size: page_size.unwrap_or(1024),
        },
    };
    if let Some(v) = value("--padding") {
        opts.padding = v.parse().expect("--padding");
    }
    let (positions, indices, polygons, uvs, prefix) = match args.first() {
        Some(path) => {
            let (p, i, poly, uv) = load_obj(&fs::read_to_string(path).expect("read input"));
            let prefix = args
                .get(1)
                .cloned()
                .unwrap_or_else(|| path.trim_end_matches(".obj").to_string() + "_unwrapped");
            (p, i, Some(poly), uv, prefix)
        }
        None => {
            let (p, i) = common::torus();
            fs::create_dir_all("out").unwrap();
            (p, i, None, None, "out/torus".to_string())
        }
    };

    let (positions, indices) = if flat {
        flatten(&positions, &indices)
    } else {
        (positions, indices)
    };
    let uvs = if keep_uvs && !flat {
        Some(uvs.expect("--keep-uvs: the OBJ has no vt for every vertex"))
    } else {
        None
    };

    let start = Instant::now();
    let mesh = uvunwrap::MeshInput {
        instance_scales: &instances,
        existing_uvs: uvs.as_deref(),
        polygons: polygons.as_deref(),
        ..uvunwrap::MeshInput::new(&positions, &indices)
    };
    let atlas = uvunwrap::generate(&[mesh], &opts).expect("unwrap failed");
    let elapsed = start.elapsed();
    let out = &atlas.meshes[0];
    println!(
        "{} triangles -> {} charts, {} vertices ({} in), {}x{} x{} page(s), {:.4} texels/unit, {:.1}% utilization, {:.1} ms",
        indices.len() / 3,
        atlas.chart_count,
        out.vertices.len(),
        positions.len(),
        atlas.width,
        atlas.height,
        atlas.page_count,
        atlas.texels_per_unit,
        atlas.utilization * 100.0,
        elapsed.as_secs_f64() * 1000.0
    );
    println!("output hash {:016x}", common::hash(&atlas));

    let mut obj = String::new();
    for v in &out.vertices {
        let p = positions[v.xref as usize];
        writeln!(obj, "v {} {} {}", p[0], p[1], p[2]).unwrap();
    }
    for v in &out.vertices {
        writeln!(obj, "vt {} {}", v.uv[0], 1.0 - v.uv[1]).unwrap(); // OBJ's v points up
    }
    for t in out.indices.chunks_exact(3) {
        let [a, b, c] = [t[0] + 1, t[1] + 1, t[2] + 1];
        writeln!(obj, "f {a}/{a} {b}/{b} {c}/{c}").unwrap();
    }
    fs::write(format!("{prefix}.obj"), obj).unwrap();

    for page in 0..atlas.page_count {
        let scale = 1024.0 / atlas.width.max(atlas.height) as f32;
        let (w, h) = (atlas.width as f32 * scale, atlas.height as f32 * scale);
        let mut svg = format!(
            "<svg xmlns='http://www.w3.org/2000/svg' width='{w}' height='{h}' viewBox='0 0 {w} {h}'>\
             <rect width='100%' height='100%' fill='#1b1b1f'/>"
        );
        // Draw the mesh once, or once per instance rectangle.
        let views: Vec<Option<uvunwrap::InstanceRect>> = if out.instances.is_empty() {
            vec![None]
        } else {
            out.instances.iter().copied().map(Some).collect()
        };
        for view in views {
            for t in out.indices.chunks_exact(3) {
                let vs = [0, 1, 2].map(|k| out.vertices[t[k] as usize]);
                let Some(chart) = vs[0].chart else { continue };
                let on_page = view.map_or(vs[0].page, |r| Some(r.page));
                if on_page != Some(page) {
                    continue;
                }
                let uv = |uv: [f32; 2]| match view {
                    None => uv,
                    Some(r) => [0, 1].map(|k| r.min[k] + uv[k] * (r.max[k] - r.min[k])),
                };
                let hue = (chart as f32 * 137.508) % 360.0; // golden-angle palette
                let pts: Vec<String> = vs
                    .iter()
                    .map(|v| {
                        let p = uv(v.uv);
                        format!(
                            "{:.2},{:.2}",
                            p[0] * atlas.width as f32 * scale,
                            p[1] * atlas.height as f32 * scale
                        )
                    })
                    .collect();
                write!(svg, "<polygon points='{}' fill='hsl({hue:.0},65%,60%)' stroke='hsl({hue:.0},65%,35%)' stroke-width='0.3'/>", pts.join(" ")).unwrap();
            }
        }
        svg.push_str("</svg>");
        fs::write(format!("{prefix}_page{page}.svg"), svg).unwrap();
    }
    println!("wrote {prefix}.obj and {} SVG page(s)", atlas.page_count);
}