tess2-rust 1.1.0

Pure Rust port of libtess2 — complete SGI polygon tessellation pipeline with winding rules, self-intersections, and multiple output modes
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

// Copyright 2025 Lars Brubaker
// Tests for Constrained Delaunay Triangulation (CDT) option.

mod helpers;

use tess2_rust::{ElementType, TessOption, Tessellator, WindingRule};

fn tessellate_with_cdt(vertices: &[f64], cdt: bool) -> Tessellator {
    let mut tess = Tessellator::new();
    tess.set_option(TessOption::ConstrainedDelaunayTriangulation, cdt);
    tess.add_contour(2, vertices);
    let ok = tess.tessellate(WindingRule::Positive, ElementType::Polygons, 3, 2, None);
    assert!(ok, "tessellation failed (cdt={})", cdt);
    tess
}

#[test]
fn cdt_quad_produces_valid_output() {
    let quad = &[0.0f64, 0.0, 10.0, 0.0, 10.0, 10.0, 0.0, 10.0];
    let tess = tessellate_with_cdt(quad, true);
    assert_eq!(
        tess.element_count(),
        2,
        "quad should produce 2 triangles with CDT"
    );
    helpers::verify_valid_output(&tess);
}

#[test]
fn cdt_triangle_produces_one_triangle() {
    let tri = &[0.0f64, 0.0, 1.0, 0.0, 0.0, 1.0];
    let tess = tessellate_with_cdt(tri, true);
    assert_eq!(tess.element_count(), 1);
    helpers::verify_valid_output(&tess);
}

#[test]
fn cdt_preserves_area() {
    let quad = &[0.0f64, 0.0, 10.0, 0.0, 10.0, 10.0, 0.0, 10.0];
    let tess_normal = tessellate_with_cdt(quad, false);
    let tess_cdt = tessellate_with_cdt(quad, true);

    let area_normal = helpers::total_tessellation_area(&tess_normal);
    let area_cdt = helpers::total_tessellation_area(&tess_cdt);

    assert!(
        (area_normal - area_cdt).abs() < 0.01,
        "CDT and normal should produce same area: {} vs {}",
        area_normal,
        area_cdt
    );
}

#[test]
fn cdt_complex_polygon() {
    let data = include_str!("data/dude.dat");
    let contours = helpers::parse_contours(data);

    let mut tess = Tessellator::new();
    tess.set_option(TessOption::ConstrainedDelaunayTriangulation, true);
    for contour in &contours {
        tess.add_contour(2, contour);
    }
    let ok = tess.tessellate(WindingRule::Positive, ElementType::Polygons, 3, 2, None);
    assert!(ok, "CDT tessellation of dude should succeed");
    helpers::verify_valid_output(&tess);
    assert!(tess.element_count() > 0, "CDT should produce triangles");

    let area = helpers::total_tessellation_area(&tess);
    assert!(area > 0.0, "CDT dude should have non-zero area");
}

#[test]
fn cdt_star() {
    let data = include_str!("data/star.dat");
    let contours = helpers::parse_contours(data);

    let mut tess_normal = Tessellator::new();
    for contour in &contours {
        tess_normal.add_contour(2, contour);
    }
    let ok = tess_normal.tessellate(WindingRule::Odd, ElementType::Polygons, 3, 2, None);
    assert!(ok);

    let mut tess_cdt = Tessellator::new();
    tess_cdt.set_option(TessOption::ConstrainedDelaunayTriangulation, true);
    for contour in &contours {
        tess_cdt.add_contour(2, contour);
    }
    let ok = tess_cdt.tessellate(WindingRule::Odd, ElementType::Polygons, 3, 2, None);
    assert!(ok);

    helpers::verify_valid_output(&tess_cdt);

    let area_normal = helpers::total_tessellation_area(&tess_normal);
    let area_cdt = helpers::total_tessellation_area(&tess_cdt);
    assert!(
        (area_normal - area_cdt).abs() < 1.0,
        "CDT and normal star areas should be similar: {} vs {}",
        area_normal,
        area_cdt
    );
}

#[test]
fn cdt_polygon_with_hole() {
    // Tessellate with CDT - outer square with inner hole
    let mut tess = Tessellator::new();
    tess.set_option(TessOption::ConstrainedDelaunayTriangulation, true);
    tess.set_option(TessOption::ReverseContours, false);
    tess.add_contour(2, &[0.0f64, 0.0, 10.0, 0.0, 10.0, 10.0, 0.0, 10.0]);
    tess.set_option(TessOption::ReverseContours, true);
    tess.add_contour(2, &[3.0f64, 3.0, 7.0, 3.0, 7.0, 7.0, 3.0, 7.0]);

    let ok = tess.tessellate(WindingRule::Positive, ElementType::Polygons, 3, 2, None);
    assert!(ok, "CDT polygon with hole should succeed");
    helpers::verify_valid_output(&tess);
    assert!(tess.element_count() > 0, "CDT should produce triangles");

    let area = helpers::total_tessellation_area(&tess);
    assert!(
        area > 0.0,
        "CDT polygon with hole should have positive area"
    );
}

#[test]
fn cdt_toggle_does_not_crash() {
    // Toggle CDT on/off between tessellations (reuse check).
    let quad = &[0.0f64, 0.0, 5.0, 0.0, 5.0, 5.0, 0.0, 5.0];

    let mut tess = Tessellator::new();
    tess.set_option(TessOption::ConstrainedDelaunayTriangulation, true);
    tess.add_contour(2, quad);
    let _ = tess.tessellate(WindingRule::Positive, ElementType::Polygons, 3, 2, None);

    let mut tess2 = Tessellator::new();
    tess2.set_option(TessOption::ConstrainedDelaunayTriangulation, false);
    tess2.add_contour(2, quad);
    let ok = tess2.tessellate(WindingRule::Positive, ElementType::Polygons, 3, 2, None);
    assert!(ok);
}