OBJ: New C++ based wavefront OBJ importer

This takes state of soc-2020-io-performance branch as it was at
e9bbfd0c8c7 (2021 Oct 31), merges latest master (2022 Apr 4),
adds a bunch of tests, and fixes a bunch of stuff found by said
tests. The fixes are detailed in the differential.

Timings on my machine (Windows, VS2022 release build, AMD Ryzen
5950X 32 threads):

- Rungholt minecraft level (269MB file, 1 mesh): 54.2s -> 14.2s
  (memory usage: 7.0GB -> 1.9GB).
- Blender 3.0 splash scene: "I waited for 90 minutes and gave up"
  -> 109s. Now, this time is not great, but at least 20% of the
  time is spent assigning unique names for the imported objects
  (the scene has 24 thousand objects). This is not specific to obj
  importer, but rather a general issue across blender overall.

Test suite file updates done in Subversion tests repository.

Reviewed By: @howardt, @sybren
Differential Revision: https://developer.blender.org/D13958

1 files changed, 111 insertions, 0 deletions

diff --git a/source/blender/io/wavefront_obj/importer/obj_import_objects.hh b/source/blender/io/wavefront_obj/importer/obj_import_objects.hh
new file mode 100644
index 00000000000..c6ce7d3c434
--- /dev/null
+++ b/source/blender/io/wavefront_obj/importer/obj_import_objects.hh
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup obj
+ */
+
+#pragma once
+
+#include "BKE_lib_id.h"
+
+#include "BLI_math_vec_types.hh"
+#include "BLI_vector.hh"
+#include "BLI_vector_set.hh"
+
+#include "DNA_meshdata_types.h"
+#include "DNA_object_types.h"
+
+namespace blender::io::obj {
+
+/**
+ * List of all vertex and UV vertex coordinates in an OBJ file accessible to any
+ * Geometry instance at any time.
+ */
+struct GlobalVertices {
+  Vector<float3> vertices;
+  Vector<float2> uv_vertices;
+  Vector<float3> vertex_normals;
+};
+
+/**
+ * Keeps track of the vertices that belong to other Geometries.
+ * Needed only for MLoop.v and MEdge.v1 which needs vertex indices ranging from (0 to total
+ * vertices in the mesh) as opposed to the other OBJ indices ranging from (0 to total vertices
+ * in the global list).
+ */
+struct VertexIndexOffset {
+ private:
+  int offset_ = 0;
+
+ public:
+  void set_index_offset(const int64_t total_vertices)
+  {
+    offset_ = total_vertices;
+  }
+  int64_t get_index_offset() const
+  {
+    return offset_;
+  }
+};
+
+/**
+ * A face's corner in an OBJ file. In Blender, it translates to a mloop vertex.
+ */
+struct PolyCorner {
+  /* These indices range from zero to total vertices in the OBJ file. */
+  int vert_index;
+  /* -1 is to indicate absence of UV vertices. Only < 0 condition should be checked since
+   * it can be less than -1 too. */
+  int uv_vert_index = -1;
+  int vertex_normal_index = -1;
+};
+
+struct PolyElem {
+  std::string vertex_group;
+  std::string material_name;
+  bool shaded_smooth = false;
+  Vector<PolyCorner> face_corners;
+};
+
+/**
+ * Contains data for one single NURBS curve in the OBJ file.
+ */
+struct NurbsElement {
+  /**
+   * For curves, groups may be used to specify multiple splines in the same curve object.
+   * It may also serve as the name of the curve if not specified explicitly.
+   */
+  std::string group_;
+  int degree = 0;
+  /**
+   * Indices into the global list of vertex coordinates. Must be non-negative.
+   */
+  Vector<int> curv_indices;
+  /* Values in the parm u/v line in a curve definition. */
+  Vector<float> parm;
+};
+
+enum eGeometryType {
+  GEOM_MESH = OB_MESH,
+  GEOM_CURVE = OB_CURVES_LEGACY,
+};
+
+struct Geometry {
+  eGeometryType geom_type_ = GEOM_MESH;
+  std::string geometry_name_;
+  VectorSet<std::string> material_names_;
+  /**
+   * Indices in the vector range from zero to total vertices in a geometry.
+   * Values range from zero to total coordinates in the global list.
+   */
+  Vector<int> vertex_indices_;
+  /** Edges written in the file in addition to (or even without polygon) elements. */
+  Vector<MEdge> edges_;
+  Vector<PolyElem> face_elements_;
+  bool has_vertex_normals_ = false;
+  bool use_vertex_groups_ = false;
+  NurbsElement nurbs_element_;
+  int total_loops_ = 0;
+};
+
+}  // namespace blender::io::obj