100 lines
2 KiB
C++
100 lines
2 KiB
C++
#include <psemek/gfx/obj_parser.hpp>
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#include <psemek/util/to_string.hpp>
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#include <psemek/util/exception.hpp>
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#include <string>
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#include <sstream>
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#include <stdexcept>
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namespace psemek::gfx
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{
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obj_data parse_obj(std::istream & is)
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{
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std::vector<math::point<float, 3>> positions;
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std::vector<math::vector<float, 2>> texcoords;
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std::vector<math::vector<float, 3>> normals;
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obj_data result;
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std::string line;
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std::size_t line_count = 0;
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auto fail = [&](auto const & ... args){
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throw util::exception(util::to_string("Error parsing OBJ data, line ", line_count, ": ", args...));
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};
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while (std::getline(is >> std::ws, line))
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{
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++line_count;
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if (line.empty()) continue;
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if (line[0] == '#') continue;
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std::istringstream ls(std::move(line));
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std::string tag;
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ls >> tag;
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if (tag == "v")
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{
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auto & p = positions.emplace_back();
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ls >> p[0] >> p[1] >> p[2];
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}
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else if (tag == "vt")
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{
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auto & t = texcoords.emplace_back();
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ls >> t[0] >> t[1];
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}
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else if (tag == "vn")
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{
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auto & n = normals.emplace_back();
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ls >> n[0] >> n[1] >> n[2];
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}
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else if (tag == "f")
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{
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std::vector<obj_data::vertex> vertices;
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while (ls)
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{
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std::size_t ip, it, in;
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ls >> ip;
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if (ls.eof()) break;
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if (!ls || ls.get() != '/')
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fail("expected '/'");
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ls >> it;
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if (!ls || ls.get() != '/')
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fail("expected '/'");
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ls >> in;
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--ip;
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--it;
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--in;
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if (ip >= positions.size())
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fail("bad position index (", ip, ")");
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if (it >= texcoords.size())
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fail("bad texcoord index (", ip, ")");
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if (in >= normals.size())
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fail("bad normal index (", ip, ")");
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auto & v = vertices.emplace_back();
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v.position = positions[ip];
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v.texcoord = texcoords[it];
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v.normal = normals[in];
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}
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for (std::size_t i = 1; i + 1 < vertices.size(); ++i)
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{
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result.triangles.push_back({{vertices[0], vertices[i], vertices[i + 1]}});
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}
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}
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}
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return result;
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}
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}
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