Mesh: replace saacos with acosf for normal calculation

The clamped version of acos isn't needed as degenerate (nan) coordinates
result in zeroed vectors which don't need clamping.

1 files changed, 9 insertions, 5 deletions

diff --git a/source/blender/blenkernel/intern/mesh_normals.cc b/source/blender/blenkernel/intern/mesh_normals.cc
index 9a761c6fa11..aae50fa165e 100644
--- a/source/blender/blenkernel/intern/mesh_normals.cc
+++ b/source/blender/blenkernel/intern/mesh_normals.cc
@@ -230,8 +230,10 @@ static void mesh_calc_normals_poly_and_vertex_accum_fn(
         copy_v3_v3(edvec_next, edvec_end);
       }
 
-      /* Calculate angle between the two poly edges incident on this vertex. */
-      const float fac = saacos(-dot_v3v3(edvec_prev, edvec_next));
+      /* Calculate angle between the two poly edges incident on this vertex.
+       * NOTE: no need for #saacos here as the input has been sanitized,
+       * `nan` values in coordinates normalize to zero which works for `acosf`. */
+      const float fac = acosf(-dot_v3v3(edvec_prev, edvec_next));
       const float vnor_add[3] = {pnor[0] * fac, pnor[1] * fac, pnor[2] * fac};
 
       add_v3_v3_atomic(vnors[ml[i_curr].v], vnor_add);
@@ -1156,9 +1158,11 @@ static void split_loop_nor_fan_do(LoopSplitTaskDataCommon *common_data, LoopSpli
     // printf("\thandling edge %d / loop %d\n", mlfan_curr->e, mlfan_curr_index);
 
     {
-      /* Code similar to accumulate_vertex_normals_poly_v3. */
-      /* Calculate angle between the two poly edges incident on this vertex. */
-      const float fac = saacos(dot_v3v3(vec_curr, vec_prev));
+      /* Code similar to #accumulate_vertex_normals_poly_v3. */
+      /* Calculate angle between the two poly edges incident on this vertex.
+       * NOTE: no need for #saacos here as the input has been sanitized,
+       * `nan` values in coordinates normalize to zero which works for `acosf`. */
+      const float fac = acosf(dot_v3v3(vec_curr, vec_prev));
       /* Accumulate */
       madd_v3_v3fl(lnor, polynors[mpfan_curr_index], fac);