xref: /libCEED/examples/rust/ex1-volume-vector/src/transform.rs (revision 3eb59678ecb8a0fe884fb9297a6048221d053835)
1*3eb59678SJeremy L Thompson // Copyright (c) 2017-2025, Lawrence Livermore National Security, LLC and other CEED contributors.
2*3eb59678SJeremy L Thompson // All Rights Reserved. See the top-level LICENSE and NOTICE files for details.
3*3eb59678SJeremy L Thompson //
4*3eb59678SJeremy L Thompson // SPDX-License-Identifier: BSD-2-Clause
5*3eb59678SJeremy L Thompson //
6*3eb59678SJeremy L Thompson // This file is part of CEED:  http://github.com/ceed
7*3eb59678SJeremy L Thompson 
8*3eb59678SJeremy L Thompson // ----------------------------------------------------------------------------
9*3eb59678SJeremy L Thompson // Transform mesh coordinates
10*3eb59678SJeremy L Thompson // ----------------------------------------------------------------------------
11*3eb59678SJeremy L Thompson pub(crate) fn transform_mesh_coordinates(
12*3eb59678SJeremy L Thompson     dim: usize,
13*3eb59678SJeremy L Thompson     mesh_size: usize,
14*3eb59678SJeremy L Thompson     mesh_coords: &mut libceed::Vector,
15*3eb59678SJeremy L Thompson ) -> libceed::Result<libceed::Scalar> {
16*3eb59678SJeremy L Thompson     // Transform coordinates
17*3eb59678SJeremy L Thompson     if dim == 1 {
18*3eb59678SJeremy L Thompson         for coord in mesh_coords.view_mut()?.iter_mut() {
19*3eb59678SJeremy L Thompson             // map [0,1] to [0,1] varying the mesh density
20*3eb59678SJeremy L Thompson             *coord = 0.5
21*3eb59678SJeremy L Thompson                 + 1.0 / (3.0 as libceed::Scalar).sqrt()
22*3eb59678SJeremy L Thompson                     * ((2.0 / 3.0) * std::f64::consts::PI as libceed::Scalar * (*coord - 0.5)).sin()
23*3eb59678SJeremy L Thompson         }
24*3eb59678SJeremy L Thompson     } else {
25*3eb59678SJeremy L Thompson         let mut coords = mesh_coords.view_mut()?;
26*3eb59678SJeremy L Thompson         let num_nodes = mesh_size / dim;
27*3eb59678SJeremy L Thompson         for i in 0..num_nodes {
28*3eb59678SJeremy L Thompson             // map (x,y) from [0,1]x[0,1] to the quarter annulus with polar
29*3eb59678SJeremy L Thompson             // coordinates, (r,phi) in [1,2]x[0,pi/2] with area = 3/4*pi
30*3eb59678SJeremy L Thompson             let u = 1.0 + coords[i];
31*3eb59678SJeremy L Thompson             let v = std::f64::consts::PI as libceed::Scalar / 2.0 * coords[i + num_nodes];
32*3eb59678SJeremy L Thompson             coords[i] = u * v.cos();
33*3eb59678SJeremy L Thompson             coords[i + num_nodes] = u * v.sin();
34*3eb59678SJeremy L Thompson         }
35*3eb59678SJeremy L Thompson     }
36*3eb59678SJeremy L Thompson 
37*3eb59678SJeremy L Thompson     // Exact volume of transformed region
38*3eb59678SJeremy L Thompson     let exact_volume = match dim {
39*3eb59678SJeremy L Thompson         1 => 1.0,
40*3eb59678SJeremy L Thompson         2 | 3 => 3.0 / 4.0 * std::f64::consts::PI as libceed::Scalar,
41*3eb59678SJeremy L Thompson         _ => unreachable!(),
42*3eb59678SJeremy L Thompson     };
43*3eb59678SJeremy L Thompson     Ok(exact_volume)
44*3eb59678SJeremy L Thompson }
45*3eb59678SJeremy L Thompson 
46*3eb59678SJeremy L Thompson // ----------------------------------------------------------------------------
47