OBJ: further optimize, cleanup and harden the new C++ importer

Continued improvements to the new C++ based OBJ importer.

Performance: about 2x faster.
- Rungholt.obj (several meshes, 263MB file): Windows 12.7s -> 5.9s, Mac 7.7s -> 3.1s.
- Blender 3.0 splash (24k meshes, 2.4GB file): Windows 97.3s -> 53.6s, Mac 137.3s -> 80.0s.
- "Windows" is VS2022, AMD Ryzen 5950X (32 threads), "Mac" is Xcode/clang 13, M1Max (10 threads).
- Slightly reduced memory usage during import as well.

The performance gains are a combination of several things:
- Replacing `std::stof` / `std::stoi` with C++17 `from_chars`.
- Stop reading input file char-by-char using `std::getline`, and instead read in 64kb chunks, and parse from there (taking care of possibly handling lines split mid-way due to chunk boundaries).
- Removing abstractions for splitting a line by some char,
- Avoid tiny memory allocations: instead of storing a vector of polygon corners in each face, store all the corners in one big array, and per-face only store indices "where do corners start, and how many". Likewise, don't store full string names of material/group names for each face; only store indices into overall material/group names arrays.
- Stop always doing mesh validation, which is slow. Do it just like the Alembic importer does: only do validation if found some invalid faces during import, or if requested by the user via an import setting checkbox (which defaults to off).
- Stop doing "collection sync" for each object being added; instead do the collection sync right after creating all the objects.

Cleanup / Robustness:

This reworking of parser (see "removing abstractions" point above) means that all the functions that were in `parser_string_utils` file are gone, and replaced with different set of functions. However they are not OBJ specific, so as pointed out during review of the previous differential, they are now in `source/blender/io/common` library.

Added gtest coverage for said functions as well; something that was only indirectly covered by obj tests previously.

Rework of some bits of parsing made the parser actually better able to deal with invalid syntax. E.g. previously, if a face corner were a `/123` string, it would have incorrectly treated that as a vertex index (since it would get "hey that's one number" after splitting a string by a slash), instead of properly marking it as invalid syntax.

Added gtest coverage for .mtl parsing; something that was not covered by any tests at all previously.

Reviewed By: Howard Trickey
Differential Revision: https://developer.blender.org/D14586

1 files changed, 0 insertions, 54 deletions

diff --git a/source/blender/io/wavefront_obj/importer/parser_string_utils.hh b/source/blender/io/wavefront_obj/importer/parser_string_utils.hh
deleted file mode 100644
index 62cfbebccf3..00000000000
--- a/source/blender/io/wavefront_obj/importer/parser_string_utils.hh
+++ /dev/null
@@ -1,54 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-
-namespace blender::io::obj {
-
-/* Note: these OBJ parser helper functions are planned to get fairly large
- * changes "soon", so don't read too much into current implementation... */
-
-/**
- * Store multiple lines separated by an escaped newline character: `\\n`.
- * Use this before doing any parse operations on the read string.
- */
-void read_next_line(std::fstream &file, std::string &r_line);
-/**
- * Split a line string into the first word (key) and the rest of the line.
- * Also remove leading & trailing spaces as well as `\r` carriage return
- * character if present.
- */
-void split_line_key_rest(StringRef line, StringRef &r_line_key, StringRef &r_rest_line);
-/**
- * Split the given string by the delimiter and fill the given vector.
- * If an intermediate string is empty, or space or null character, it is not appended to the
- * vector.
- */
-void split_by_char(StringRef in_string, const char delimiter, Vector<StringRef> &r_out_list);
-/**
- * Convert the given string to float and assign it to the destination value.
- *
- * If the string cannot be converted to a float, the fallback value is used.
- */
-void copy_string_to_float(StringRef src, const float fallback_value, float &r_dst);
-/**
- * Convert all members of the Span of strings to floats and assign them to the float
- * array members. Usually used for values like coordinates.
- *
- * If a string cannot be converted to a float, the fallback value is used.
- */
-void copy_string_to_float(Span<StringRef> src,
-                          const float fallback_value,
-                          MutableSpan<float> r_dst);
-/**
- * Convert the given string to int and assign it to the destination value.
- *
- * If the string cannot be converted to an integer, the fallback value is used.
- */
-void copy_string_to_int(StringRef src, const int fallback_value, int &r_dst);
-/**
- * Convert the given strings to ints and fill the destination int buffer.
- *
- * If a string cannot be converted to an integer, the fallback value is used.
- */
-void copy_string_to_int(Span<StringRef> src, const int fallback_value, MutableSpan<int> r_dst);
-std::string replace_all_occurences(StringRef original, StringRef to_remove, StringRef to_add);
-
-}  // namespace blender::io::obj