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

mod delaunay;
mod polygon;
mod ray;

use fj_interop::{debug::DebugInfo, mesh::Mesh};
use fj_math::Point;

use crate::{shape::Shape, topology::Face};

use self::polygon::Polygon;

use super::{FaceApprox, Tolerance};

/// Triangulate a shape
pub fn triangulate(
    mut shape: Shape,
    tolerance: Tolerance,
    debug_info: &mut DebugInfo,
) -> Mesh<Point<3>> {
    let mut mesh = Mesh::new();

    for face in shape.topology().faces() {
        let face = face.get();
        match &face {
            Face::Face { surface, color, .. } => {
                let surface = surface.get();
                let approx = FaceApprox::new(&face, tolerance);

                let points: Vec<_> = approx
                    .points
                    .into_iter()
                    .map(|vertex| {
                        // Can't panic, unless the approximation wrongfully
                        // generates points that are not in the surface.
                        surface.point_model_to_surface(vertex)
                    })
                    .collect();
                let face_as_polygon = Polygon::new(surface)
                    .with_exterior(approx.exterior.points.into_iter().map(
                        |point| {
                            // Can't panic, unless the approximation wrongfully
                            // generates points that are not in the surface.
                            surface.point_model_to_surface(point).native()
                        },
                    ))
                    .with_interiors(approx.interiors.into_iter().map(
                        |interior| {
                            interior.points.into_iter().map(|point| {
                                // Can't panic, unless the approximation
                                // wrongfully generates points that are not in
                                // the surface.
                                surface.point_model_to_surface(point).native()
                            })
                        },
                    ));

                let mut triangles = delaunay::triangulate(points);
                triangles.retain(|triangle| {
                    face_as_polygon.contains_triangle(
                        triangle.map(|point| point.native()),
                        debug_info,
                    )
                });

                for triangle in triangles {
                    let points = triangle.map(|point| point.canonical());
                    mesh.push_triangle(points, *color);
                }
            }
            Face::Triangles(triangles) => {
                for &(triangle, color) in triangles {
                    mesh.push_triangle(triangle.points(), color);
                }
            }
        }
    }

    mesh
}

#[cfg(test)]
mod tests {
    use fj_interop::{debug::DebugInfo, mesh::Mesh};
    use fj_math::{Point, Scalar};

    use crate::{
        algorithms::Tolerance, geometry::Surface, shape::Shape, topology::Face,
    };

    #[test]
    fn simple() -> anyhow::Result<()> {
        let mut shape = Shape::new();

        let a = [0., 0., 0.];
        let b = [2., 0., 0.];
        let c = [2., 2., 0.];
        let d = [0., 1., 0.];

        Face::builder(Surface::x_y_plane(), &mut shape)
            .with_exterior_polygon([a, b, c, d])
            .build()?;

        let triangles = triangulate(shape);
        assert!(triangles.contains_triangle([a, b, d]));
        assert!(triangles.contains_triangle([b, c, d]));
        assert!(!triangles.contains_triangle([a, b, c]));
        assert!(!triangles.contains_triangle([a, c, d]));

        Ok(())
    }

    #[test]
    fn simple_hole() -> anyhow::Result<()> {
        let mut shape = Shape::new();

        let a = [0., 0., 0.];
        let b = [4., 0., 0.];
        let c = [4., 4., 0.];
        let d = [0., 4., 0.];

        let e = [1., 1., 0.];
        let f = [3., 1., 0.];
        let g = [3., 3., 0.];
        let h = [1., 2., 0.];

        Face::builder(Surface::x_y_plane(), &mut shape)
            .with_exterior_polygon([a, b, c, d])
            .with_interior_polygon([e, f, g, h])
            .build()?;

        let triangles = triangulate(shape);

        // Should contain some triangles from the polygon. Don't need to test
        // them all.
        assert!(triangles.contains_triangle([a, e, h]));
        assert!(triangles.contains_triangle([a, d, h]));

        // Shouldn't contain any possible triangle from the hole.
        assert!(!triangles.contains_triangle([e, f, g]));
        assert!(!triangles.contains_triangle([e, g, h]));
        assert!(!triangles.contains_triangle([e, f, h]));
        assert!(!triangles.contains_triangle([f, g, h]));

        Ok(())
    }

    fn triangulate(shape: Shape) -> Mesh<Point<3>> {
        let tolerance = Tolerance::from_scalar(Scalar::ONE).unwrap();

        let mut debug_info = DebugInfo::new();
        super::triangulate(shape, tolerance, &mut debug_info)
    }
}