honeycomb_kernels/grisubal/routines/
clip.rs

1//! clipping operation routines
2
3use std::collections::{HashSet, VecDeque};
4
5use honeycomb_core::cmap::{CMap2, DartIdType, FaceIdType, NULL_DART_ID, OrbitPolicy};
6use honeycomb_core::geometry::{CoordsFloat, Vertex2};
7
8use crate::grisubal::GrisubalError;
9use crate::grisubal::model::Boundary;
10
11/// Clip content on the left side of the boundary.
12pub fn clip_left<T: CoordsFloat>(cmap: &mut CMap2<T>) -> Result<(), GrisubalError> {
13    // color faces using a bfs starting on multiple nodes
14    let marked = mark_faces(cmap, Boundary::Left, Boundary::Right)?;
15
16    // save vertices & split boundary
17    delete_darts(cmap, marked, Boundary::Right);
18
19    Ok(())
20}
21
22/// Clip content on the right side of the boundary.
23pub fn clip_right<T: CoordsFloat>(cmap: &mut CMap2<T>) -> Result<(), GrisubalError> {
24    // color faces using a bfs starting on multiple nodes
25    let marked = mark_faces(cmap, Boundary::Right, Boundary::Left)?;
26
27    // save vertices & split boundary
28    delete_darts(cmap, marked, Boundary::Left);
29
30    Ok(())
31}
32
33// --- internals
34
35#[allow(clippy::cast_possible_truncation)]
36fn mark_faces<T: CoordsFloat>(
37    cmap: &CMap2<T>,
38    mark: Boundary,
39    other: Boundary,
40) -> Result<HashSet<FaceIdType>, GrisubalError> {
41    let mut marked: HashSet<FaceIdType> = HashSet::from([0]);
42    let mut queue: VecDeque<FaceIdType> = (1..cmap.n_darts() as DartIdType)
43        .filter_map(|dart_id| {
44            // use darts on the left side of the boundary as starting points to walk through faces
45            if cmap.force_read_attribute::<Boundary>(dart_id) == Some(mark)
46                && !cmap.is_free(dart_id)
47            {
48                return Some(cmap.face_id(dart_id));
49            }
50            None
51        })
52        .collect();
53    while let Some(face_id) = queue.pop_front() {
54        // mark faces
55        if marked.insert(face_id) {
56            // detect orientation issues / open geometries
57            let mut darts = cmap.orbit(OrbitPolicy::Face, face_id as DartIdType);
58            if darts.any(|did| cmap.force_read_attribute::<Boundary>(did) == Some(other)) {
59                return Err(GrisubalError::InconsistentOrientation(
60                    "between-boundary inconsistency",
61                ));
62            }
63            // find neighbor faces where entry darts aren't tagged
64            let darts = cmap.orbit(OrbitPolicy::Face, face_id as DartIdType);
65            queue.extend(darts.filter_map(|dart_id| {
66                if matches!(
67                    cmap.force_read_attribute::<Boundary>(cmap.beta::<2>(dart_id)),
68                    Some(Boundary::None) | None
69                ) {
70                    return Some(cmap.face_id(cmap.beta::<2>(dart_id)));
71                }
72                None
73            }));
74        }
75    }
76    marked.remove(&0);
77    Ok(marked)
78}
79
80#[allow(clippy::cast_possible_truncation)]
81fn delete_darts<T: CoordsFloat>(
82    cmap: &mut CMap2<T>,
83    marked: HashSet<FaceIdType>,
84    kept_boundary: Boundary,
85) {
86    let kept_boundary_components: Vec<(DartIdType, Vertex2<T>)> = (1..cmap.n_darts() as DartIdType)
87        .filter_map(|dart_id| {
88            if cmap.force_read_attribute::<Boundary>(dart_id) == Some(kept_boundary) {
89                return Some((
90                    dart_id,
91                    cmap.force_read_vertex(cmap.vertex_id(dart_id))
92                        .expect("E: found a topological vertex with no associated coordinates"),
93                ));
94            }
95            None
96        })
97        .collect();
98
99    for face_id in marked {
100        let darts: Vec<DartIdType> = cmap
101            .orbit(OrbitPolicy::Face, face_id as DartIdType)
102            .collect();
103        for &dart in &darts {
104            let _ = cmap.force_remove_vertex(cmap.vertex_id(dart));
105            cmap.set_betas(dart, [NULL_DART_ID; 3]);
106            cmap.remove_free_dart(dart);
107        }
108    }
109
110    for (dart, vertex) in kept_boundary_components {
111        cmap.set_beta::<2>(dart, NULL_DART_ID); // set beta2(dart) to 0
112        cmap.force_write_vertex(cmap.vertex_id(dart), vertex);
113    }
114}
honeycomb_kernels/grisubal/routines/clip.rs

honeycomb_kernels/grisubal/routines/
clip.rs
