xref: /libCEED/examples/rust/ex3-volume/src/transform.rs (revision 9ba83ac0e4b1fca39d6fa6737a318a9f0cbc172d)
1*9ba83ac0SJeremy L Thompson // Copyright (c) 2017-2026, Lawrence Livermore National Security, LLC and other CEED contributors.
23eb59678SJeremy L Thompson // All Rights Reserved. See the top-level LICENSE and NOTICE files for details.
33eb59678SJeremy L Thompson //
43eb59678SJeremy L Thompson // SPDX-License-Identifier: BSD-2-Clause
53eb59678SJeremy L Thompson //
63eb59678SJeremy L Thompson // This file is part of CEED:  http://github.com/ceed
73eb59678SJeremy L Thompson 
83eb59678SJeremy L Thompson // ----------------------------------------------------------------------------
93eb59678SJeremy L Thompson // Transform mesh coordinates
103eb59678SJeremy L Thompson // ----------------------------------------------------------------------------
113eb59678SJeremy L Thompson pub(crate) fn transform_mesh_coordinates(
123eb59678SJeremy L Thompson     dim: usize,
133eb59678SJeremy L Thompson     mesh_size: usize,
143eb59678SJeremy L Thompson     mesh_coords: &mut libceed::Vector,
153eb59678SJeremy L Thompson ) -> libceed::Result<libceed::Scalar> {
163eb59678SJeremy L Thompson     // Transform coordinates
173eb59678SJeremy L Thompson     match dim {
183eb59678SJeremy L Thompson         1 => {
193eb59678SJeremy L Thompson             for coord in mesh_coords.view_mut()?.iter_mut() {
203eb59678SJeremy L Thompson                 // map [0,1] to [0,1] varying the mesh density
213eb59678SJeremy L Thompson                 *coord = 0.5
223eb59678SJeremy L Thompson                     + 1.0 / (3.0 as libceed::Scalar).sqrt()
233eb59678SJeremy L Thompson                         * ((2.0 / 3.0) * std::f64::consts::PI as libceed::Scalar * (*coord - 0.5))
243eb59678SJeremy L Thompson                             .sin()
253eb59678SJeremy L Thompson             }
263eb59678SJeremy L Thompson         }
273eb59678SJeremy L Thompson         _ => {
283eb59678SJeremy L Thompson             let num_nodes = mesh_size / dim;
293eb59678SJeremy L Thompson             let mut coords = mesh_coords.view_mut()?;
303eb59678SJeremy L Thompson             for i in 0..num_nodes {
313eb59678SJeremy L Thompson                 // map (x,y) from [0,1]x[0,1] to the quarter annulus with polar
323eb59678SJeremy L Thompson                 // coordinates, (r,phi) in [1,2]x[0,pi/2] with area = 3/4*pi
333eb59678SJeremy L Thompson                 let u = coords[i] + 1.;
343eb59678SJeremy L Thompson                 let v = coords[i + num_nodes] * std::f64::consts::PI / 2.;
353eb59678SJeremy L Thompson                 coords[i] = u * v.cos();
363eb59678SJeremy L Thompson                 coords[i + num_nodes] = u * v.sin();
373eb59678SJeremy L Thompson             }
383eb59678SJeremy L Thompson         }
393eb59678SJeremy L Thompson     }
403eb59678SJeremy L Thompson 
413eb59678SJeremy L Thompson     // Exact volume of transformed region
423eb59678SJeremy L Thompson     let exact_volume = match dim {
433eb59678SJeremy L Thompson         1 => 1.,
443eb59678SJeremy L Thompson         2 | 3 => 3. / 4. * std::f64::consts::PI,
453eb59678SJeremy L Thompson         _ => unreachable!(),
463eb59678SJeremy L Thompson     };
473eb59678SJeremy L Thompson     Ok(exact_volume)
483eb59678SJeremy L Thompson }
493eb59678SJeremy L Thompson 
503eb59678SJeremy L Thompson // ----------------------------------------------------------------------------
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