Add a new C++ version of an exporter for the Wavefront .obj format.

This was originally written by Ankit Meel as a GSoC 2020 project.
Howard Trickey added some tests and made some corrections/modifications.
See D13046 for more details.

This commit inserts a new menu item into the export menu called
"Wavefront OBJ (.obj) - New".
For now the old Python exporter remains in the menu, along with
the Python importer, but we plan to remove it soon (leaving the
old addon bundled with Blender but not enabled by default).

1 files changed, 132 insertions, 0 deletions

diff --git a/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.hh b/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.hh
new file mode 100644
index 00000000000..36d35ae370b
--- /dev/null
+++ b/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.hh
@@ -0,0 +1,132 @@
+/*
+ * This program 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 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup obj
+ */
+
+#pragma once
+
+#include "DNA_meshdata_types.h"
+
+#include "BLI_map.hh"
+#include "BLI_vector.hh"
+
+#include "IO_wavefront_obj.h"
+#include "obj_export_io.hh"
+#include "obj_export_mtl.hh"
+
+namespace blender::io::obj {
+
+class OBJCurve;
+class OBJMesh;
+/**
+ * Total vertices/ UV vertices/ normals of previous Objects
+ * should be added to the current Object's indices.
+ */
+struct IndexOffsets {
+  int vertex_offset;
+  int uv_vertex_offset;
+  int normal_offset;
+};
+
+/**
+ * Responsible for writing a .OBJ file.
+ */
+class OBJWriter : NonMovable, NonCopyable {
+ private:
+  const OBJExportParams &export_params_;
+  std::unique_ptr<FileHandler<eFileType::OBJ>> file_handler_ = nullptr;
+  IndexOffsets index_offsets_{0, 0, 0};
+
+ public:
+  OBJWriter(const char *filepath, const OBJExportParams &export_params) noexcept(false)
+      : export_params_(export_params)
+  {
+    file_handler_ = std::make_unique<FileHandler<eFileType::OBJ>>(filepath);
+  }
+
+  void write_header() const;
+
+  void write_object_name(const OBJMesh &obj_mesh_data) const;
+  void write_object_group(const OBJMesh &obj_mesh_data) const;
+  void write_mtllib_name(const StringRefNull mtl_filepath) const;
+  void write_vertex_coords(const OBJMesh &obj_mesh_data) const;
+  void write_uv_coords(OBJMesh &obj_mesh_data) const;
+  void write_poly_normals(const OBJMesh &obj_mesh_data) const;
+  int write_smooth_group(const OBJMesh &obj_mesh_data,
+                         int poly_index,
+                         const int last_poly_smooth_group) const;
+  int16_t write_poly_material(const OBJMesh &obj_mesh_data,
+                              const int poly_index,
+                              const int16_t last_poly_mat_nr,
+                              std::function<const char *(int)> matname_fn) const;
+  int16_t write_vertex_group(const OBJMesh &obj_mesh_data,
+                             const int poly_index,
+                             const int16_t last_poly_vertex_group) const;
+  void write_poly_elements(const OBJMesh &obj_mesh_data,
+                           std::function<const char *(int)> matname_fn);
+  void write_edges_indices(const OBJMesh &obj_mesh_data) const;
+  void write_nurbs_curve(const OBJCurve &obj_nurbs_data) const;
+
+  void update_index_offsets(const OBJMesh &obj_mesh_data);
+
+ private:
+  using func_vert_uv_normal_indices = void (OBJWriter::*)(Span<int> vert_indices,
+                                                          Span<int> uv_indices,
+                                                          Span<int> normal_indices) const;
+  func_vert_uv_normal_indices get_poly_element_writer(const int total_uv_vertices) const;
+
+  void write_vert_uv_normal_indices(Span<int> vert_indices,
+                                    Span<int> uv_indices,
+                                    Span<int> normal_indices) const;
+  void write_vert_normal_indices(Span<int> vert_indices,
+                                 Span<int> /*uv_indices*/,
+                                 Span<int> normal_indices) const;
+  void write_vert_uv_indices(Span<int> vert_indices,
+                             Span<int> uv_indices,
+                             Span<int> /*normal_indices*/) const;
+  void write_vert_indices(Span<int> vert_indices,
+                          Span<int> /*uv_indices*/,
+                          Span<int> /*normal_indices*/) const;
+};
+
+/**
+ * Responsible for writing a .MTL file.
+ */
+class MTLWriter : NonMovable, NonCopyable {
+ private:
+  std::unique_ptr<FileHandler<eFileType::MTL>> file_handler_ = nullptr;
+  std::string mtl_filepath_;
+  Vector<MTLMaterial> mtlmaterials_;
+  /* Map from a Material* to an index into mtlmaterials_. */
+  Map<const Material *, int> material_map_;
+
+ public:
+  MTLWriter(const char *obj_filepath) noexcept(false);
+
+  void write_header(const char *blen_filepath) const;
+  void write_materials();
+  StringRefNull mtl_file_path() const;
+  Vector<int> add_materials(const OBJMesh &mesh_to_export);
+  const char *mtlmaterial_name(int index);
+
+ private:
+  void write_bsdf_properties(const MTLMaterial &mtl_material);
+  void write_texture_map(const MTLMaterial &mtl_material,
+                         const Map<const eMTLSyntaxElement, tex_map_XX>::Item &texture_map);
+};
+}  // namespace blender::io::obj