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Mesh: Merge by Distance: Remove unnecessary array

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The `groups_map` array (which indicates the group an element belongs
to) is only intended to reduce loops when creating groups, speeding up
that part of the code.

But on the downside, it requires more memory usage, and adds one more
step to access groups (`groups_offs[groups_map[i]]` instead of just
`groups_offs[i]`).

So removing that array decreases memory usage and speeds up access in
another part of the code.

The profile showed a +6% advantage when the Weld modifier affects large
portions of the mesh.

But it also showed a loss of around -0.6% in performance for cases
where the Weld modifier affects small parts of the mesh.

The biggest benefit is to save memory and speed up some cases.
This commit is contained in:
Germano Cavalcante
2023-07-10 23:21:52 -03:00
parent bef652c432
commit 7aa31c884d
1 changed files with 15 additions and 40 deletions
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55
source/blender/geometry/intern/mesh_merge_by_distance.cc
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@@ -1283,48 +1283,26 @@ static void weld_mesh_context_create(const Mesh &mesh,
*/
static void merge_groups_create(Span<int> dest_map,
Span<int> double_elems,
Array<int> &r_groups_map,
Array<int> &r_groups_buffer,
Array<int> &r_groups_offsets)
MutableSpan<int> r_groups_offsets,
Array<int> &r_groups_buffer)
{
r_groups_map.reinitialize(dest_map.size());
r_groups_map.fill(OUT_OF_CONTEXT);
int wgroups_len = 0;
for (const int elem_orig : double_elems) {
const int elem_dest = dest_map[elem_orig];
if (elem_dest == elem_orig) {
r_groups_map[elem_orig] = wgroups_len;
wgroups_len++;
}
else {
r_groups_map[elem_orig] = ELEM_MERGED;
}
}
if (wgroups_len == 0) {
/* All elems in the context are collapsed or do not form groups. */
return;
}
/* Add +1 to allow calculation of the length of the last group. */
r_groups_offsets = Array<int>(wgroups_len + 1, 0);
BLI_assert(r_groups_offsets.size() == dest_map.size() + 1);
r_groups_offsets.fill(0);
/* TODO: Check using #array_utils::count_indices instead. At the moment it cannot be used
* because `dest_map` has negative values and `double_elems` (which indicates only the indexes to
* be read) is not used. */
for (const int elem_orig : double_elems) {
const int elem_dest = dest_map[elem_orig];
const int group_index = r_groups_map[elem_dest];
r_groups_offsets[group_index]++;
r_groups_offsets[elem_dest]++;
}
int offs = 0;
for (const int i : IndexRange(wgroups_len)) {
for (const int i : dest_map.index_range()) {
offs += r_groups_offsets[i];
r_groups_offsets[i] = offs;
}
r_groups_offsets[wgroups_len] = offs;
r_groups_offsets.last() = offs;
r_groups_buffer.reinitialize(offs);
BLI_assert(r_groups_buffer.size() == double_elems.size());
@@ -1333,8 +1311,7 @@ static void merge_groups_create(Span<int> dest_map,
for (int i = double_elems.size(); i--;) {
const int elem_orig = double_elems[i];
const int elem_dest = dest_map[elem_orig];
const int group_index = r_groups_map[elem_dest];
r_groups_buffer[--r_groups_offsets[group_index]] = elem_orig;
r_groups_buffer[--r_groups_offsets[elem_dest]] = elem_orig;
}
}
@@ -1460,16 +1437,14 @@ static void merge_customdata_all(const CustomData *source,
const int source_size = dest_map.size();
MutableSpan<int> groups_map;
Array<int> groups_buffer, groups_offs_;
MutableSpan<int> groups_offs_;
Array<int> groups_buffer;
if (do_mix_data) {
merge_groups_create(dest_map, double_elems, r_final_map, groups_buffer, groups_offs_);
r_final_map.reinitialize(source_size + 1);
/**
* Be careful when setting values to this array as it uses the same buffer as #r_final_map.
* This map will be used to adjust the index of vertices and edges in the new edges and loops.
*/
groups_map = r_final_map;
/* Be careful when setting values to this array as it uses the same buffer as `r_final_map`. */
groups_offs_ = r_final_map;
merge_groups_create(dest_map, double_elems, groups_offs_, groups_buffer);
}
else {
r_final_map.reinitialize(source_size);
@@ -1495,7 +1470,7 @@ static void merge_customdata_all(const CustomData *source,
}
if (dest_map[i] == i) {
if (do_mix_data) {
const IndexRange grp_buffer_range = groups_offs[groups_map[i]];
const IndexRange grp_buffer_range = groups_offs[i];
customdata_weld(source,
dest,
&groups_buffer[grp_buffer_range.start()],