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- /*
- * Copyright (C) 2021 Christopher J. Howard
- *
- * This file is part of Antkeeper source code.
- *
- * Antkeeper source code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * Antkeeper source code is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
- */
-
- #include "mesh-functions.hpp"
- #include "math/math.hpp"
- #include <unordered_map>
-
- namespace geom {
-
- struct edge_hasher
- {
- std::size_t operator()(const std::array<std::size_t, 2>& v) const noexcept
- {
- std::size_t hash = std::hash<std::size_t>()(v[0]);
- return hash ^ (std::hash<std::size_t>()(v[1]) + 0x9e3779b9 + (hash << 6) + (hash >> 2));
- }
- };
-
- void create_triangle_mesh(mesh& mesh, const std::vector<float3>& vertices, const std::vector<std::array<std::uint_fast32_t, 3>>& triangles)
- {
- for (const auto& vertex: vertices)
- mesh.add_vertex(vertex);
-
- std::unordered_map<std::array<std::size_t, 2>, geom::mesh::edge*, edge_hasher> edge_map;
- const std::vector<mesh::vertex*>& mesh_vertices = mesh.get_vertices();
- std::vector<geom::mesh::edge*> loop(3);
-
- for (const auto& triangle: triangles)
- {
- geom::mesh::vertex* triangle_vertices[3] =
- {
- mesh_vertices[triangle[0]],
- mesh_vertices[triangle[1]],
- mesh_vertices[triangle[2]]
- };
-
- for (int j = 0; j < 3; ++j)
- {
- geom::mesh::vertex* start = triangle_vertices[j];
- geom::mesh::vertex* end = triangle_vertices[(j + 1) % 3];
-
- if (auto it = edge_map.find({start->index, end->index}); it != edge_map.end())
- {
- loop[j] = it->second;
- }
- else
- {
- loop[j] = mesh.add_edge(start, end);
- edge_map[{start->index, end->index}] = loop[j];
- edge_map[{end->index, start->index}] = loop[j]->symmetric;
- }
-
- }
-
- mesh.add_face(loop);
- }
- }
-
- void calculate_face_normals(float3* normals, const mesh& mesh)
- {
- const std::vector<mesh::face*>& faces = mesh.get_faces();
-
- for (std::size_t i = 0; i < faces.size(); ++i)
- {
- const mesh::face& face = *(faces[i]);
- const float3& a = face.edge->vertex->position;
- const float3& b = face.edge->next->vertex->position;
- const float3& c = face.edge->previous->vertex->position;
-
- normals[i] = math::normalize(math::cross(b - a, c - a));
- }
- }
-
- float3 calculate_face_normal(const mesh::face& face)
- {
- const float3& a = face.edge->vertex->position;
- const float3& b = face.edge->next->vertex->position;
- const float3& c = face.edge->previous->vertex->position;
- return math::normalize(math::cross(b - a, c - a));
- }
-
- void calculate_vertex_tangents(float4* tangents, const float2* texcoords, const float3* normals, const mesh& mesh)
- {
- const std::vector<mesh::face*>& faces = mesh.get_faces();
- const std::vector<mesh::vertex*>& vertices = mesh.get_vertices();
-
- // Allocate tangent and bitangent buffers
- float3* tangent_buffer = new float3[vertices.size()];
- float3* bitangent_buffer = new float3[vertices.size()];
- for (std::size_t i = 0; i < vertices.size(); ++i)
- {
- tangent_buffer[i] = {0.0f, 0.0f, 0.0f};
- bitangent_buffer[i] = {0.0f, 0.0f, 0.0f};
- }
-
- // Accumulate tangents and bitangents
- for (std::size_t i = 0; i < faces.size(); ++i)
- {
- const mesh::face& face = *(faces[i]);
- std::size_t ia = face.edge->vertex->index;
- std::size_t ib = face.edge->next->vertex->index;
- std::size_t ic = face.edge->previous->vertex->index;
- const float3& a = vertices[ia]->position;
- const float3& b = vertices[ib]->position;
- const float3& c = vertices[ic]->position;
- const float2& uva = texcoords[ia];
- const float2& uvb = texcoords[ib];
- const float2& uvc = texcoords[ic];
-
- float3 ba = b - a;
- float3 ca = c - a;
- float2 uvba = uvb - uva;
- float2 uvca = uvc - uva;
-
- float f = 1.0f / (uvba.x * uvca.y - uvca.x * uvba.y);
- float3 tangent = (ba * uvca.y - ca * uvba.y) * f;
- float3 bitangent = (ba * -uvca.x + ca * uvba.x) * f;
-
- tangent_buffer[ia] += tangent;
- tangent_buffer[ib] += tangent;
- tangent_buffer[ic] += tangent;
- bitangent_buffer[ia] += bitangent;
- bitangent_buffer[ib] += bitangent;
- bitangent_buffer[ic] += bitangent;
- }
-
- // Orthogonalize tangents
- for (std::size_t i = 0; i < vertices.size(); ++i)
- {
- const float3& n = normals[i];
- const float3& t = tangent_buffer[i];
- const float3& b = bitangent_buffer[i];
-
- // Gram-Schmidt orthogonalize tangent
- float3 tangent = math::normalize(t - n * math::dot(n, t));
-
- // Calculate bitangent sign
- float bitangent_sign = (math::dot(math::cross(n, t), b) < 0.0f) ? -1.0f : 1.0f;
-
- tangents[i] = {tangent.x, tangent.y, tangent.z, bitangent_sign};
- }
-
- // Free faceted tangents and bitangents
- delete[] tangent_buffer;
- delete[] bitangent_buffer;
- }
-
- aabb<float> calculate_bounds(const mesh& mesh)
- {
- float3 bounds_min;
- float3 bounds_max;
- for (int i = 0; i < 3; ++i)
- {
- bounds_min[i] = std::numeric_limits<float>::infinity();
- bounds_max[i] = -std::numeric_limits<float>::infinity();
- }
-
- for (const mesh::vertex* vertex: mesh.get_vertices())
- {
- const auto& position = vertex->position;
- for (int i = 0; i < 3; ++i)
- {
- bounds_min[i] = std::min<float>(bounds_min[i], position[i]);
- bounds_max[i] = std::max<float>(bounds_max[i], position[i]);
- }
- }
-
- return aabb<float>{bounds_min, bounds_max};
- }
-
- } // namespace geom
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