| 11 | using namespace PyMesh; |
| 12 | |
| 13 | void FaceAreaAttribute::compute_from_mesh(Mesh& mesh) { |
| 14 | const size_t dim = mesh.get_dim(); |
| 15 | const size_t num_faces = mesh.get_num_faces(); |
| 16 | const size_t num_vertex_per_face = mesh.get_vertex_per_face(); |
| 17 | |
| 18 | VectorF& areas = m_values; |
| 19 | areas = VectorF::Zero(num_faces); |
| 20 | const auto& vertices = mesh.get_vertices(); |
| 21 | const auto& faces = mesh.get_faces(); |
| 22 | |
| 23 | auto compute_2D_triangle_area = [&vertices,&faces](size_t i) { |
| 24 | const auto& face = faces.segment<3>(i*3); |
| 25 | const auto& v0 = vertices.segment<2>(face[0]*2); |
| 26 | const auto& v1 = vertices.segment<2>(face[1]*2); |
| 27 | const auto& v2 = vertices.segment<2>(face[2]*2); |
| 28 | |
| 29 | return (v0[0]*v1[1] + v1[0]*v2[1] + v2[0]*v0[1] |
| 30 | -v0[1]*v1[0] - v1[1]*v2[0] - v2[1]*v0[0]) * 0.5; |
| 31 | }; |
| 32 | auto compute_3D_triangle_area = [&vertices,&faces](size_t i) { |
| 33 | const auto& face = faces.segment<3>(i*3); |
| 34 | const auto& v0 = vertices.segment<3>(face[0]*3); |
| 35 | const auto& v1 = vertices.segment<3>(face[1]*3); |
| 36 | const auto& v2 = vertices.segment<3>(face[2]*3); |
| 37 | |
| 38 | const auto a = (v1-v0).norm(); |
| 39 | const auto b = (v2-v1).norm(); |
| 40 | const auto c = (v0-v2).norm(); |
| 41 | return 0.25 * sqrt(std::max(0.0, (a+b+c) * (-a+b+c) * (a-b+c) * (a+b-c))); |
| 42 | }; |
| 43 | auto compute_2D_quad_area = [&vertices, &faces](size_t i) { |
| 44 | const auto& face = faces.segment<4>(i*4); |
| 45 | const auto& v0 = vertices.segment<2>(face[0]*2); |
| 46 | const auto& v1 = vertices.segment<2>(face[1]*2); |
| 47 | const auto& v2 = vertices.segment<2>(face[2]*2); |
| 48 | const auto& v3 = vertices.segment<2>(face[3]*2); |
| 49 | const Vector2F c = (v0 + v1 + v2 + v3) * 0.25; |
| 50 | |
| 51 | return (c[0]*v1[1] + v1[0]*v2[1] + v2[0]*c[1] |
| 52 | -c[1]*v1[0] - v1[1]*v2[0] - v2[1]*c[0] + |
| 53 | c[0]*v2[1] + v2[0]*v3[1] + v3[0]*c[1] |
| 54 | -c[1]*v2[0] - v2[1]*v3[0] - v3[1]*c[0] + |
| 55 | c[0]*v3[1] + v3[0]*v0[1] + v0[0]*c[1] |
| 56 | -c[1]*v3[0] - v3[1]*v0[0] - v0[1]*c[0] + |
| 57 | c[0]*v0[1] + v0[0]*v1[1] + v1[0]*c[1] |
| 58 | -c[1]*v0[0] - v0[1]*v1[0] - v1[1]*c[0]) * 0.5; |
| 59 | }; |
| 60 | auto compute_3D_quad_area = [&vertices, &faces](size_t i) { |
| 61 | const auto& face = faces.segment<4>(i*4); |
| 62 | const auto& v0 = vertices.segment<3>(face[0]*3); |
| 63 | const auto& v1 = vertices.segment<3>(face[1]*3); |
| 64 | const auto& v2 = vertices.segment<3>(face[2]*3); |
| 65 | const auto& v3 = vertices.segment<3>(face[3]*3); |
| 66 | const Vector3F c = (v0 + v1 + v2 + v3) * 0.25; |
| 67 | |
| 68 | return (((v2 - c).cross(v1 - c)).norm() + |
| 69 | ((v3 - c).cross(v2 - c)).norm() + |
| 70 | ((v0 - c).cross(v3 - c)).norm() + |
no test coverage detected