honeycomb_kernels/grisubal/
mod.rs

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
263
264
265
266
267
//! *GRISUBAL* algorithm description & implementation
//!
//! This module contain all code used to implement our grid submersion algorithm, or *GRISUBAL*
//! for short.
//!
//! This algorithm builds the mesh of a geometry by overlapping a grid over it and intersecting
//! the grid with the geometry. It is inspired by the approach described in
//! [this](https://internationalmeshingroundtable.com/assets/research-notes/imr32/2011.pdf)
//! research note.
//!
//! # Assumptions / Hypotheses
//!
//! Boundaries are consistently oriented, i.e.:
//! - normals of segments making up a boundary all point outward / inward, no mix
//! - boundaries are closed
//! - if there are nested boundaries, their orientation are consistent one with the other; this is
//!   an extension of the first condition
//!
//! # Algorithm
//!
//! The steps followed by the algorithm are detailed in the user guide. The following is a summary.
//!
//! ## Pre-processing
//!
//! 1. Compute characteristics of a grid covering the entire geometry, avoiding exact intersection
//!    between the grid's segments and the geometry's vertices.
//! 2. Remove "redundant" Points of Interest to avoid duplicated vertices.
//! 3. Check for obvious orientation issues (open geometry & orientation per boundary).
//!
//! ## Main kernel
//!
//! 1. Compute intersection vertices between the geometry's segments and the grid.
//! 2. Insert given intersections into the grid.
//! 3. Build new edge data by searching through the original segments.
//! 4. Insert the new edges into the map. Mark darts on each side of the edge with the `Boundary`
//!    attribute.
//!
//! ## Post-processing clip
//!
//! Depending on the specified argument, one side (or the other) of the boundary can be clipped.
//! This is specified using the [`Clip`] enum; The following steps describe the operation for
//! [`Clip::Left`].
//!
//! 1. Fetch all darts marked as `Boundary::Left` during the last step of the main kernel.
//! 2. Use these darts' faces as starting point for a coloring algorithm. The search is done using
//!    a BFS and only consider adjacent faces if the adjacent dart isn't marked as a boundary.
//!    This step is also used to check for orientation inconsistencies, most importantly orientation
//!    across distinct boundaries.
//! 3. Delete all darts making up the marked faces.
//!
//! The `Boundary` attribute is then removed from the map before return.

// ------ MODULE DECLARATIONS

pub(crate) mod model;
pub(crate) mod routines;
pub(crate) mod timers;

// ------ IMPORTS

use crate::grisubal::{
    model::{Boundary, Geometry2},
    routines::{
        clip_left, clip_right, compute_intersection_ids, compute_overlapping_grid,
        detect_orientation_issue, generate_edge_data, generate_intersection_data,
        group_intersections_per_edge, insert_edges_in_map, insert_intersections,
        remove_redundant_poi,
    },
    timers::{finish, start_timer, unsafe_time_section},
};
use honeycomb_core::{
    cmap::{CMapBuilder, GridDescriptor},
    prelude::{CMap2, CoordsFloat},
};
use thiserror::Error;
use vtkio::Vtk;

// ------ CONTENT

/// Post-processing clip operation.
///
/// Note that the part of the map that is clipped depends on the orientation of the original geometry provided as
/// input.
#[derive(Default)]
pub enum Clip {
    /// Clip elements located on the left side of the oriented boundary.
    Left,
    /// Clip elements located on the right side of the oriented boundary.
    Right,
    /// Keep all elements. Default value.
    #[default]
    None,
}

#[derive(Error, Debug)]
/// Enum used to model potential errors of the `grisubal` kernel.
///
/// Each variant has an associated message that details more precisely what was detected.
pub enum GrisubalError {
    /// An orientation issue has been detected in the input geometry.
    #[error("boundary isn't consistently oriented - {0}")]
    InconsistentOrientation(&'static str),
    /// The specified geometry does not match one (or more) requirements of the algorithm.
    #[error("input shape isn't conform to requirements - {0}")]
    InvalidShape(&'static str),
    /// The VTK file used to try to build a `Geometry2` object contains invalid data
    /// (per VTK's specification).
    #[error("invalid/corrupted data in the vtk file - {0}")]
    BadVtkData(&'static str),
    /// The VTK file used to try to build a `Geometry2` object contains valid but unsupported data.
    #[error("unsupported data in the vtk file - {0}")]
    UnsupportedVtkData(&'static str),
}

#[allow(clippy::missing_errors_doc)]
/// Main algorithm call function.
///
/// # Arguments
///
/// - `file_path: impl AsRef<Path>` -- Path to a VTK file describing input geometry. See
///   [VTK Format] for more information about the expected formatting.
/// - `grid_cell_sizes: [T; 2],` -- Desired grid cell size along the X/Y axes.
/// - `clip: Option<Clip>` -- Indicates which part of the map should be clipped, if any, in
///   the post-processing phase. For more information on the clipping process, see [`Clip`].
///
/// ## VTK Format
///
/// At the moment, the input geometry should be specified via a file under the VTK Legacy format.
/// Just like the `io` feature provided in the core crate, there are a few additional requirements
/// for the geometry to be loaded correctly:
/// - The geometry should have a consistent orientation, i.e. the order in which the points are
///   given should form normals with a consistent direction (either pointing inward or outward the
///   geometry).
/// - The geometry should be described using in an `UnstructuredGrid` data set, with supported
///   cell types (`Vertex`, `Line`). Lines will be interpreted as the boundary to match while
///   vertices will be considered as points of interests.
///
/// # Return / Errors
///
/// This function returns a `Result` taking the following values:
/// - `Ok(CMap2)` -- Algorithm ran successfully.
/// - `Err(GrisubalError)` -- Algorithm encountered an issue. See [`GrisubalError`] for more
///   information about possible errors.
///
/// # Panics
///
/// This function may panic if the specified file cannot be opened.
///
/// # Example
///
/// ```no_run
/// # use honeycomb_core::prelude::CMap2;
/// # use honeycomb_kernels::grisubal::*;
/// # fn main() -> Result<(), GrisubalError>{
/// let cmap: CMap2<f64> = grisubal("some/path/to/geometry.vtk", [1., 1.], Clip::default())?;
/// # Ok(())
/// # }
/// ```
#[allow(clippy::needless_pass_by_value)]
pub fn grisubal<T: CoordsFloat>(
    file_path: impl AsRef<std::path::Path>,
    grid_cell_sizes: [T; 2],
    clip: Clip,
) -> Result<CMap2<T>, GrisubalError> {
    // INIT TIMER
    start_timer!(instant);

    // --- IMPORT VTK INPUT
    let geometry_vtk = match Vtk::import(file_path) {
        Ok(vtk) => vtk,
        Err(e) => panic!("E: could not open specified vtk file - {e}"),
    };
    unsafe_time_section!(instant, timers::Section::ImportVTK);
    //----/

    // --- BUILD OUR MODEL FROM THE VTK IMPORT
    let mut geometry = Geometry2::try_from(geometry_vtk)?;
    unsafe_time_section!(instant, timers::Section::BuildGeometry);
    //----/

    // --- FIRST DETECTION OF ORIENTATION ISSUES
    detect_orientation_issue(&geometry)?;
    unsafe_time_section!(instant, timers::Section::DetectOrientation);
    //----/

    // --- FIND AN OVERLAPPING GRID
    let ([nx, ny], origin) = compute_overlapping_grid(&geometry, grid_cell_sizes)?;
    let [cx, cy] = grid_cell_sizes;
    let ogrid = GridDescriptor::default()
        .n_cells_x(nx)
        .n_cells_y(ny)
        .len_per_cell_x(cx)
        .len_per_cell_y(cy)
        .origin(origin);
    unsafe_time_section!(instant, timers::Section::ComputeOverlappingGrid);
    //----/

    // --- REMOVE REDUNDANT PoIs
    remove_redundant_poi(&mut geometry, grid_cell_sizes, origin);
    unsafe_time_section!(instant, timers::Section::RemoveRedundantPoi);
    //----/

    // ------ START MAIN KERNEL TIMER
    start_timer!(kernel);

    // --- BUILD THE GRID
    let mut cmap = CMapBuilder::default()
        .grid_descriptor(ogrid)
        .add_attribute::<Boundary>() // will be used for clipping
        .build()
        .expect("E: unreachable"); // unreachable because grid dims are valid
    unsafe_time_section!(instant, timers::Section::BuildMeshInit);
    //----/

    // process the geometry

    // --- STEP 1 & 2
    // (1)
    let (new_segments, intersection_metadata) =
        generate_intersection_data(&cmap, &geometry, [nx, ny], [cx, cy], origin);
    // (2)
    let n_intersec = intersection_metadata.len();
    let (edge_intersec, dart_slices) =
        group_intersections_per_edge(&mut cmap, intersection_metadata);
    let intersection_darts = compute_intersection_ids(n_intersec, &edge_intersec, &dart_slices);
    unsafe_time_section!(instant, timers::Section::BuildMeshIntersecData);
    //----/

    // --- STEP 3
    insert_intersections(&mut cmap, &edge_intersec, &dart_slices);
    unsafe_time_section!(instant, timers::Section::BuildMeshInsertIntersec);
    //----/

    // --- STEP 4
    let edges = generate_edge_data(&cmap, &geometry, &new_segments, &intersection_darts);
    unsafe_time_section!(instant, timers::Section::BuildMeshEdgeData);
    //----/

    // --- STEP 5
    insert_edges_in_map(&mut cmap, &edges);
    unsafe_time_section!(instant, timers::Section::BuildMeshInsertEdge);
    //----/

    unsafe_time_section!(kernel, timers::Section::BuildMeshTot);
    //-------/

    // --- CLIP
    match clip {
        Clip::Left => clip_left(&mut cmap)?,
        Clip::Right => clip_right(&mut cmap)?,
        Clip::None => {}
    }
    unsafe_time_section!(instant, timers::Section::Clip);
    //----/

    // CLEANUP
    cmap.remove_attribute_storage::<Boundary>();
    finish!(instant);
    //-/

    Ok(cmap)
}

// ------ TESTS

#[cfg(test)]
mod tests;