Fix for [#24237] Hair dynamics with zero particles generates a segmentation fault

3 files changed, 16 insertions, 6 deletions

diff --git a/source/blender/blenkernel/intern/particle.c b/source/blender/blenkernel/intern/particle.c
index 723ff7faed3..ebbb3ea1020 100644
--- a/source/blender/blenkernel/intern/particle.c
+++ b/source/blender/blenkernel/intern/particle.c
@@ -402,6 +402,7 @@ void free_hair(Object *ob, ParticleSystem *psys, int dynamics)
 			modifier_free((ModifierData*)psys->clmd);
 			
 			psys->clmd = NULL;
+			psys->pointcache = BKE_ptcache_add(&psys->ptcaches);
 		}
 		else {
 			cloth_free_modifier(ob, psys->clmd);
diff --git a/source/blender/blenkernel/intern/particle_system.c b/source/blender/blenkernel/intern/particle_system.c
index 47a220dcefb..fa82d2c5359 100644
--- a/source/blender/blenkernel/intern/particle_system.c
+++ b/source/blender/blenkernel/intern/particle_system.c
@@ -4016,8 +4016,13 @@ void particle_system_update(Scene *scene, Object *ob, ParticleSystem *psys)
 	switch(part->type) {
 		case PART_HAIR:
 		{
+			/* nothing to do so bail out early */
+			if(psys->totpart == 0 && part->totpart == 0) {
+				psys_free_path_cache(psys, NULL);
+				free_hair(ob, psys, 0);
+			}
 			/* (re-)create hair */
-			if(hair_needs_recalc(psys)) {
+			else if(hair_needs_recalc(psys)) {
 				float hcfra=0.0f;
 				int i, recalc = psys->recalc;
 
diff --git a/source/blender/blenkernel/intern/pointcache.c b/source/blender/blenkernel/intern/pointcache.c
index a15e66ed843..f9d2c1c3fec 100644
--- a/source/blender/blenkernel/intern/pointcache.c
+++ b/source/blender/blenkernel/intern/pointcache.c
@@ -2993,13 +2993,17 @@ void BKE_ptcache_update_info(PTCacheID *pid)
 
 void BKE_ptcache_validate(PointCache *cache, int framenr)
 {
-	cache->flag |= PTCACHE_SIMULATION_VALID;
-	cache->simframe = framenr;
+	if(cache) {
+		cache->flag |= PTCACHE_SIMULATION_VALID;
+		cache->simframe = framenr;
+	}
 }
 void BKE_ptcache_invalidate(PointCache *cache)
 {
-	cache->flag &= ~PTCACHE_SIMULATION_VALID;
-	cache->simframe = 0;
-	cache->last_exact = MIN2(cache->startframe, 0);
+	if(cache) {
+		cache->flag &= ~PTCACHE_SIMULATION_VALID;
+		cache->simframe = 0;
+		cache->last_exact = MIN2(cache->startframe, 0);
+	}
 }