BMesh: support face-normal calculation in normal & looptri functions

Support calculating face normals when tessellating. When this is done
before updating vertex normals it gives ~20% performance improvement.

Now vertex normal calculation only needs to perform a single pass on the
mesh vertices when called after tessellation.

Extended versions of normal & looptri update functions have been added:

- BM_mesh_calc_tessellation_ex
- BM_mesh_normals_update_ex

Most callers don't need to be aware of this detail by using:

- BKE_editmesh_looptri_and_normals_calc
- BKE_editmesh_looptri_and_normals_calc_with_partial

- EDBM_update also takes advantage of this,
  where calling EDBM_update with calc_looptri & calc_normals
  enabled uses the faster normal updating logic.

1 files changed, 12 insertions, 0 deletions

diff --git a/source/blender/bmesh/intern/bmesh_mesh_normals.h b/source/blender/bmesh/intern/bmesh_mesh_normals.h
index 41191340e9e..ecd627d4bfe 100644
--- a/source/blender/bmesh/intern/bmesh_mesh_normals.h
+++ b/source/blender/bmesh/intern/bmesh_mesh_normals.h
@@ -22,7 +22,19 @@
 
 #include "bmesh_class.h"
 
+struct BMeshNormalsUpdate_Params {
+  /**
+   * When calculating tessellation as well as normals, tessellate & calculate face normals
+   * for improved performance. See #BMeshCalcTessellation_Params
+   */
+  bool face_normals;
+};
+
+void BM_mesh_normals_update_ex(BMesh *bm, const struct BMeshNormalsUpdate_Params *param);
 void BM_mesh_normals_update(BMesh *bm);
+void BM_mesh_normals_update_with_partial_ex(BMesh *bm,
+                                            const struct BMPartialUpdate *bmpinfo,
+                                            const struct BMeshNormalsUpdate_Params *param);
 void BM_mesh_normals_update_with_partial(BMesh *bm, const struct BMPartialUpdate *bmpinfo);
 
 void BM_verts_calc_normal_vcos(BMesh *bm,