Fix T59339: Particle render without baking issues

The issue was caused by dependency graph resetting particles
when evaluating copy-on-write version of object. Solved by
only doing reset from dependency graph on user edits.

Other issue was caused by modifier itself trying to compare
topology and reset particles when number of vertices or faces
changed. This isn't reliable, since topology might change even
with same number of elements. But also, since copy-on-written
object initially always have those fields zero-ed the reset
was happening on every F12.

The latter issue is solved by moving reset from modifier stack
to places where we exit edit/paint modes which might be changing
topology.

There is still weird issue of particles generated at some
weird location after tapping tab twice, but this is not a new
issue in 2.8 branch and is to be looked separately.

6 files changed, 26 insertions, 13 deletions

diff --git a/source/blender/blenkernel/BKE_particle.h b/source/blender/blenkernel/BKE_particle.h
index c23aa2f709c..72170da4ea2 100644
--- a/source/blender/blenkernel/BKE_particle.h
+++ b/source/blender/blenkernel/BKE_particle.h
@@ -418,6 +418,9 @@ typedef void (*ParticleSystemIDFunc)(struct ParticleSystem *psys, struct ID **id
 
 void BKE_particlesystem_id_loop(struct ParticleSystem *psys, ParticleSystemIDFunc func, void *userdata);
 
+/* Reset all particle systems in the given object. */
+void BKE_particlesystem_reset_all(struct Object *object);
+
 /* ----------- functions needed only inside particlesystem ------------ */
 /* particle.c */
 void psys_disable_all(struct Object *ob);
diff --git a/source/blender/blenkernel/intern/particle_system.c b/source/blender/blenkernel/intern/particle_system.c
index 458aec77379..f61786903f8 100644
--- a/source/blender/blenkernel/intern/particle_system.c
+++ b/source/blender/blenkernel/intern/particle_system.c
@@ -4414,6 +4414,18 @@ void BKE_particlesystem_id_loop(ParticleSystem *psys, ParticleSystemIDFunc func,
 	}
 }
 
+void BKE_particlesystem_reset_all(struct Object *object)
+{
+	for (ModifierData *md = object->modifiers.first; md != NULL; md = md->next) {
+		if (md->type != eModifierType_ParticleSystem) {
+			continue;
+		}
+		ParticleSystemModifierData *psmd = (ParticleSystemModifierData *)md;
+		ParticleSystem *psys = psmd->psys;
+		psys->recalc |= ID_RECALC_PSYS_RESET;
+	}
+}
+
 /* **** Depsgraph evaluation **** */
 
 void BKE_particle_settings_eval_reset(
diff --git a/source/blender/depsgraph/intern/builder/deg_builder_relations.cc b/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
index 0ca1222f5ba..a27507954fb 100644
--- a/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
+++ b/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
@@ -1705,7 +1705,10 @@ void DepsgraphRelationBuilder::build_particle_systems(Object *object)
 	ComponentKey eval_key(&object->id, NodeType::PARTICLE_SYSTEM);
 	if (BKE_ptcache_object_has(scene_, object, 0)) {
 		ComponentKey point_cache_key(&object->id, NodeType::POINT_CACHE);
-		add_relation(eval_key, point_cache_key, "Particle Point Cache");
+		add_relation(eval_key,
+		             point_cache_key,
+		             "Particle Point Cache",
+		             RELATION_FLAG_FLUSH_USER_EDIT_ONLY);
 	}
 	/* Particle systems. */
 	LISTBASE_FOREACH (ParticleSystem *, psys, &object->particlesystem) {
diff --git a/source/blender/editors/object/object_edit.c b/source/blender/editors/object/object_edit.c
index dff78d15692..958d9c08814 100644
--- a/source/blender/editors/object/object_edit.c
+++ b/source/blender/editors/object/object_edit.c
@@ -78,6 +78,7 @@
 #include "BKE_modifier.h"
 #include "BKE_object.h"
 #include "BKE_paint.h"
+#include "BKE_particle.h"
 #include "BKE_pointcache.h"
 #include "BKE_softbody.h"
 #include "BKE_editmesh.h"
@@ -537,6 +538,7 @@ bool ED_object_editmode_exit_ex(Main *bmain, Scene *scene, Object *obedit, int f
 		}
 		BLI_freelistN(&pidlist);
 
+		BKE_particlesystem_reset_all(obedit);
 		BKE_ptcache_object_reset(scene, obedit, PTCACHE_RESET_OUTDATED);
 
 		/* also flush ob recalc, doesn't take much overhead, but used for particles */
diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index d7ecfadcfc5..f3a06988f1b 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -67,7 +67,9 @@
 #include "BKE_node.h"
 #include "BKE_object.h"
 #include "BKE_paint.h"
+#include "BKE_particle.h"
 #include "BKE_pbvh.h"
+#include "BKE_pointcache.h"
 #include "BKE_report.h"
 #include "BKE_screen.h"
 #include "BKE_subsurf.h"
@@ -5569,6 +5571,9 @@ void sculpt_dynamic_topology_disable_ex(
 		ss->bm_log = NULL;
 	}
 
+	BKE_particlesystem_reset_all(ob);
+	BKE_ptcache_object_reset(scene, ob, PTCACHE_RESET_OUTDATED);
+
 	/* Refresh */
 	sculpt_update_after_dynamic_topology_toggle(depsgraph, scene, ob);
 }
diff --git a/source/blender/modifiers/intern/MOD_particlesystem.c b/source/blender/modifiers/intern/MOD_particlesystem.c
index bc1fb300cac..2c541c52919 100644
--- a/source/blender/modifiers/intern/MOD_particlesystem.c
+++ b/source/blender/modifiers/intern/MOD_particlesystem.c
@@ -187,18 +187,6 @@ static void deformVerts(
 		BKE_id_free(NULL, mesh_src);
 	}
 
-	/* report change in mesh structure */
-	if (psmd->mesh_final->totvert != psmd->totdmvert ||
-	    psmd->mesh_final->totedge != psmd->totdmedge ||
-	    psmd->mesh_final->totface != psmd->totdmface)
-	{
-		psys->recalc |= ID_RECALC_PSYS_RESET;
-
-		psmd->totdmvert = psmd->mesh_final->totvert;
-		psmd->totdmedge = psmd->mesh_final->totedge;
-		psmd->totdmface = psmd->mesh_final->totface;
-	}
-
 	if (!(ctx->object->transflag & OB_NO_PSYS_UPDATE)) {
 		struct Scene *scene = DEG_get_evaluated_scene(ctx->depsgraph);
 		psmd->flag &= ~eParticleSystemFlag_psys_updated;