Mesh: replace 'BKE_mesh_merge_verts' algorithm #105136

Merged
Germano Cavalcante merged 1 commits from mano-wii/blender:deduplicate_merge into main 2023-02-23 19:10:13 +01:00

Blender currently has 2 algorithms for merging vertices:

  • BKE_mesh_merge_verts;
  • blender::geometry::create_merged_mesh

BKE_mesh_merge_verts has a simplified algorithm to work with Array,
Mirror and Screw modifiers. It doesn't support merge results that would
create new faces. However it has shortcuts to be more efficient in
these modifiers.

blender::geometry::create_merged_mesh tries to predict all possible
outcomes. So it's a more complex. But it loses in performance to
BKE_mesh_merge_verts in some cases.

The performance comparison between these two depends on many factors.
blender::geometry::create_merged_mesh works with a context that has
only the affected geometry. Thus a smaller region of the mesh is read
for duplicate checking. Therefore, the smaller the affected geometry,
the more efficient the operation.

By my tests blender::geometry::create_merged_mesh beats
BKE_mesh_merge_verts when less than 20% of the geometry is affected
in worst case MESH_MERGE_VERTS_DUMP_IF_EQUAL or 17% in case of
MESH_MERGE_VERTS_DUMP_IF_MAPPED .

For cases where the entire geometry is affected, a 30% loss was noticed,
largely due to the creation of a context that represents the entire mesh.

Blender currently has 2 algorithms for merging vertices: - `BKE_mesh_merge_verts`; - `blender::geometry::create_merged_mesh` `BKE_mesh_merge_verts` has a simplified algorithm to work with Array, Mirror and Screw modifiers. It doesn't support merge results that would create new faces. However it has shortcuts to be more efficient in these modifiers. `blender::geometry::create_merged_mesh` tries to predict all possible outcomes. So it's a more complex. But it loses in performance to `BKE_mesh_merge_verts` in some cases. The performance comparison between these two depends on many factors. `blender::geometry::create_merged_mesh` works with a context that has only the affected geometry. Thus a smaller region of the mesh is read for duplicate checking. Therefore, the smaller the affected geometry, the more efficient the operation. By my tests `blender::geometry::create_merged_mesh` beats `BKE_mesh_merge_verts` when less than 20% of the geometry is affected in worst case `MESH_MERGE_VERTS_DUMP_IF_EQUAL` or 17% in case of `MESH_MERGE_VERTS_DUMP_IF_MAPPED` . For cases where the entire geometry is affected, a 30% loss was noticed, largely due to the creation of a context that represents the entire mesh.
Germano Cavalcante requested review from Hans Goudey 2023-02-23 16:35:05 +01:00
Hans Goudey approved these changes 2023-02-23 17:05:45 +01:00
Hans Goudey left a comment
Member

Thanks for working on this! My only constructive thought is that long term, it's a bit confusing to have vert_dest_map be passed as a mutable span rather than const (algorithms changing their inputs is often confusing). But that's not really changing here, so fine the way it is.

Thanks for working on this! My only constructive thought is that long term, it's a bit confusing to have `vert_dest_map` be passed as a mutable span rather than const (algorithms changing their inputs is often confusing). But that's not really changing here, so fine the way it is.
Member
/home/hans/blender-git/blender/source/blender/modifiers/intern/MOD_mirror.cc:71:45: warning: unused parameter ‘axis’ [-Wunused-parameter]
   71 |                                   const int axis,
      |                                   ~~~~~~~~~~^~~~
``` /home/hans/blender-git/blender/source/blender/modifiers/intern/MOD_mirror.cc:71:45: warning: unused parameter ‘axis’ [-Wunused-parameter] 71 | const int axis, | ~~~~~~~~~~^~~~
Germano Cavalcante force-pushed deduplicate_merge from 9b09023277 to a2f29efe9f 2023-02-23 19:08:18 +01:00 Compare
Germano Cavalcante merged commit 4369627e71 into main 2023-02-23 19:10:13 +01:00
Germano Cavalcante deleted branch deduplicate_merge 2023-02-23 19:10:14 +01:00
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Reference: blender/blender#105136
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