Fix T55403: Alembic: export of animated child hairs

The parent hairs were written to Alembic even when the 'Parent Particles'
checkbox (`use_parent_particles`) was disabled. In this case the parent
hairs were not correct in Blender's memory, and thus also not correct in
the exported Alembic file. The Alembic exporter now respects this setting
and doesn't write the parent hairs when 'Parent Particles' is off.

1 files changed, 6 insertions, 2 deletions

diff --git a/source/blender/alembic/intern/abc_hair.cc b/source/blender/alembic/intern/abc_hair.cc
index 38042bc7286..98387be2e61 100644
--- a/source/blender/alembic/intern/abc_hair.cc
+++ b/source/blender/alembic/intern/abc_hair.cc
@@ -79,10 +79,14 @@ void AbcHairWriter::do_write()
 
   if (m_psys->pathcache) {
     ParticleSettings *part = m_psys->part;
+    bool export_children = m_settings.export_child_hairs && m_psys->childcache &&
+                           part->childtype != 0;
 
-    write_hair_sample(mesh, part, verts, norm_values, uv_values, hvertices);
+    if (!export_children || part->draw & PART_DRAW_PARENT) {
+      write_hair_sample(mesh, part, verts, norm_values, uv_values, hvertices);
+    }
 
-    if (m_settings.export_child_hairs && m_psys->childcache) {
+    if (export_children) {
       write_hair_child_sample(mesh, part, verts, norm_values, uv_values, hvertices);
     }
   }