brep-operations.cpp

Go to the documentation of this file.

/*
 * Copyright (C) 2023  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 <engine/geom/brep/brep-operations.hpp>
#include <engine/math/vector.hpp>
#include <engine/render/vertex-attribute-location.hpp>
#include <engine/debug/log.hpp>
#include <algorithm>
#include <cmath>
 
namespace geom {
 
void generate_face_normals(brep_mesh& mesh)
{
    const auto& vertex_positions = mesh.vertices().attributes().at<math::fvec3>("position");
    auto& face_normals = static_cast<brep_attribute<math::fvec3>&>(*mesh.faces().attributes().try_emplace<math::fvec3>("normal").first);
    
    for (brep_face* face: mesh.faces())
    {
        auto loop = face->loops().begin();
        const auto& a = vertex_positions[loop->vertex()->index()];
        const auto& b = vertex_positions[(++loop)->vertex()->index()];
        const auto& c = vertex_positions[(++loop)->vertex()->index()];
        
        face_normals[face->index()] = math::normalize(math::cross(b - a, c - a));
    }
}
 
void generate_vertex_normals(brep_mesh& mesh)
{
    // Generate face normals if they don't exist
    if (!mesh.faces().attributes().contains("normal"))
    {
        generate_face_normals(mesh);
    }
    
    const auto& vertex_positions = mesh.vertices().attributes().at<math::fvec3>("position");
    const auto& face_normals = mesh.faces().attributes().at<math::fvec3>("normal");
    auto& vertex_normals = static_cast<brep_attribute<math::fvec3>&>(*mesh.vertices().attributes().try_emplace<math::fvec3>("normal").first);
    
    for (brep_vertex* vertex: mesh.vertices())
    {
        // Zero vertex normal
        auto& vertex_normal = vertex_normals[vertex->index()];
        vertex_normal = {};
        
        // Skip vertices with no edges
        if (vertex->edges().empty())
        {
            continue;
        }
        
        // Get vertex position
        const auto& vertex_position = vertex_positions[vertex->index()];
        
        // For each edge bounded by this vertex
        for (brep_edge* edge: vertex->edges())
        {
            // Skip edges with no associated face
            if (edge->loops().empty())
            {
                continue;
            }
            
            // Calculate direction vector of current edge
            const auto direction0 = math::normalize
            (
                vertex_positions[edge->vertices()[edge->vertices().front() == vertex]->index()] -
                vertex_position
            );
            
            // For each edge loop
            for (brep_loop* loop: edge->loops())
            {
                // Skip loops not originating at vertex
                if (loop->vertex() != vertex)
                {
                    continue;
                }
                
                // Calculate direction vector of previous edge
                const auto direction1 = math::normalize
                (
                    vertex_positions[loop->previous()->vertex()->index()] -
                    vertex_position
                );
                
                // Find angle between two edges
                const auto cos_edge_angle = math::dot(direction0, direction1);
                const auto edge_angle = std::acos(cos_edge_angle);
                
                // Weigh face normal by edge angle and add to vertex normal
                vertex_normal += face_normals[loop->face()->index()] * edge_angle;
            }
        }
        
        // Normalize vertex normal
        const auto sqr_length = math::sqr_length(vertex_normal);
        if (sqr_length)
        {
            vertex_normal /= std::sqrt(sqr_length);
        }
    }
}
 
void generate_loop_barycentric(brep_mesh& mesh)
{
    const auto& vertex_positions = mesh.vertices().attributes().at<math::fvec3>("position");
    auto& loop_barycentric =  static_cast<brep_attribute<math::fvec3>&>(*mesh.loops().attributes().try_emplace<math::fvec3>("barycentric").first);
    
    for (brep_face* face: mesh.faces())
    {
        auto loop = face->loops().begin();
        loop_barycentric[loop->index()] = {1.0f, 0.0f, 0.0f};
        loop_barycentric[(++loop)->index()] = {0.0f, 1.0f, 0.0f};
        loop_barycentric[(++loop)->index()] = {0.0f, 0.0f, 1.0f};
    }
}
 
std::unique_ptr<render::model> generate_model(const brep_mesh& mesh, std::shared_ptr<render::material> material)
{
    // Get vertex positions
    const geom::brep_attribute<math::fvec3>* vertex_positions = nullptr;
    if (auto attribute_it = mesh.vertices().attributes().find("position"); attribute_it != mesh.vertices().attributes().end())
    {
        vertex_positions = &static_cast<const geom::brep_attribute<math::fvec3>&>(*attribute_it);
    }
    
    // Get vertex normals
    const geom::brep_attribute<math::fvec3>* vertex_normals = nullptr;
    if (auto attribute_it = mesh.vertices().attributes().find("normal"); attribute_it != mesh.vertices().attributes().end())
    {
        vertex_normals = &static_cast<const geom::brep_attribute<math::fvec3>&>(*attribute_it);
    }
    
    // Allocate model
    auto model = std::make_unique<render::model>();
    
    // Init model bounds
    auto& bounds = model->get_bounds();
    bounds = {math::fvec3::infinity(), -math::fvec3::infinity()};
    
    // Construct model VAO
    std::size_t vertex_stride = 0;
    std::vector<gl::vertex_input_attribute> vertex_attributes;
    gl::vertex_input_attribute position_attribute{};
    if (vertex_positions)
    {
        position_attribute.location = render::vertex_attribute_location::position;
        position_attribute.binding = 0;
        position_attribute.format = gl::format::r32g32b32_sfloat;
        position_attribute.offset = 0;
        vertex_attributes.emplace_back(position_attribute);
        
        vertex_stride += 3 * sizeof(float);
    }
    gl::vertex_input_attribute normal_attribute{};
    if (vertex_normals)
    {
        normal_attribute.location = render::vertex_attribute_location::normal;
        normal_attribute.binding = 0;
        normal_attribute.format = gl::format::r32g32b32_sfloat;
        normal_attribute.offset = static_cast<std::uint32_t>(vertex_stride);
        vertex_attributes.emplace_back(normal_attribute);
        
        vertex_stride += 3 * sizeof(float);
    }
    auto& vao = model->get_vertex_array();
    vao = std::make_unique<gl::vertex_array>(vertex_attributes);
    
    // Interleave vertex data
    std::vector<std::byte> vertex_data(mesh.faces().size() * 3 * vertex_stride);
    if (vertex_positions)
    {
        std::byte* v = vertex_data.data() + position_attribute.offset;
        for (auto face: mesh.faces())
        {
            for (auto loop: face->loops())
            {
                const auto& position = (*vertex_positions)[loop->vertex()->index()];
                std::memcpy(v, position.data(), sizeof(float) * 3);
                v += vertex_stride;
                
                // Extend model bounds
                bounds.extend(position);
            }
        }
    }
    if (vertex_normals)
    {
        std::byte* v = vertex_data.data() + normal_attribute.offset;
        for (auto face: mesh.faces())
        {
            for (auto loop: face->loops())
            {
                const auto& normal = (*vertex_normals)[loop->vertex()->index()];
                std::memcpy(v, normal.data(), sizeof(float) * 3);
                v += vertex_stride;
            }
        }
    }
    
    // Construct model VBO
    auto& vbo = model->get_vertex_buffer();
    vbo = std::make_unique<gl::vertex_buffer>(gl::buffer_usage::static_draw, vertex_data);
    model->set_vertex_offset(0);
    model->set_vertex_stride(vertex_stride);
    
    // Create material group
    model->get_groups().resize(1);
    render::model_group& model_group = model->get_groups().front();
    
    model_group.id = {};
    model_group.material = material;
    model_group.primitive_topology = gl::primitive_topology::triangle_list;
    model_group.first_vertex = 0;
    model_group.vertex_count = static_cast<std::uint32_t>(mesh.faces().size() * 3);
    
    return model;
}
 
} // namespace geom