Fix T52156: Hair dynamics broken with density texture

Even strands that were excluded by the density texture were being added
to the DM passed to cloth, but these ended up having some invalid data,
because they were not fully constructed.

This simply excludes `UNEXISTED` particles from the DM generation, as
would be expected.

1 files changed, 75 insertions, 69 deletions

diff --git a/source/blender/blenkernel/intern/particle_system.c b/source/blender/blenkernel/intern/particle_system.c
index b61f6792c89..9ee456227e2 100644
--- a/source/blender/blenkernel/intern/particle_system.c
+++ b/source/blender/blenkernel/intern/particle_system.c
@@ -3042,10 +3042,12 @@ static void hair_create_input_dm(ParticleSimulationData *sim, int totpoint, int
 	/* calculate maximum segment length */
 	max_length = 0.0f;
 	LOOP_PARTICLES {
-		for (k=1, key=pa->hair+1; k<pa->totkey; k++,key++) {
-			float length = len_v3v3(key->co, (key-1)->co);
-			if (max_length < length)
-				max_length = length;
+		if (!(pa->flag & PARS_UNEXIST)) {
+			for (k=1, key=pa->hair+1; k<pa->totkey; k++,key++) {
+				float length = len_v3v3(key->co, (key-1)->co);
+				if (max_length < length)
+					max_length = length;
+			}
 		}
 	}
 	
@@ -3057,76 +3059,78 @@ static void hair_create_input_dm(ParticleSimulationData *sim, int totpoint, int
 	/* make vgroup for pin roots etc.. */
 	hair_index = 1;
 	LOOP_PARTICLES {
-		float root_mat[4][4];
-		float bending_stiffness;
-		bool use_hair;
-		
-		pa->hair_index = hair_index;
-		use_hair = psys_hair_use_simulation(pa, max_length);
-		
-		psys_mat_hair_to_object(sim->ob, sim->psmd->dm_final, psys->part->from, pa, hairmat);
-		mul_m4_m4m4(root_mat, sim->ob->obmat, hairmat);
-		normalize_m4(root_mat);
-		
-		bending_stiffness = CLAMPIS(1.0f - part->bending_random * psys_frand(psys, p + 666), 0.0f, 1.0f);
-		
-		for (k=0, key=pa->hair; k<pa->totkey; k++,key++) {
-			ClothHairData *hair;
-			float *co, *co_next;
-			
-			co = key->co;
-			co_next = (key+1)->co;
-			
-			/* create fake root before actual root to resist bending */
-			if (k==0) {
-				hair = &psys->clmd->hairdata[pa->hair_index - 1];
+		if (!(pa->flag & PARS_UNEXIST)) {
+			float root_mat[4][4];
+			float bending_stiffness;
+			bool use_hair;
+
+			pa->hair_index = hair_index;
+			use_hair = psys_hair_use_simulation(pa, max_length);
+
+			psys_mat_hair_to_object(sim->ob, sim->psmd->dm_final, psys->part->from, pa, hairmat);
+			mul_m4_m4m4(root_mat, sim->ob->obmat, hairmat);
+			normalize_m4(root_mat);
+
+			bending_stiffness = CLAMPIS(1.0f - part->bending_random * psys_frand(psys, p + 666), 0.0f, 1.0f);
+
+			for (k=0, key=pa->hair; k<pa->totkey; k++,key++) {
+				ClothHairData *hair;
+				float *co, *co_next;
+
+				co = key->co;
+				co_next = (key+1)->co;
+
+				/* create fake root before actual root to resist bending */
+				if (k==0) {
+					hair = &psys->clmd->hairdata[pa->hair_index - 1];
+					copy_v3_v3(hair->loc, root_mat[3]);
+					copy_m3_m4(hair->rot, root_mat);
+
+					hair->radius = hair_radius;
+					hair->bending_stiffness = bending_stiffness;
+
+					add_v3_v3v3(mvert->co, co, co);
+					sub_v3_v3(mvert->co, co_next);
+					mul_m4_v3(hairmat, mvert->co);
+
+					medge->v1 = pa->hair_index - 1;
+					medge->v2 = pa->hair_index;
+
+					dvert = hair_set_pinning(dvert, 1.0f);
+
+					mvert++;
+					medge++;
+				}
+
+				/* store root transform in cloth data */
+				hair = &psys->clmd->hairdata[pa->hair_index + k];
 				copy_v3_v3(hair->loc, root_mat[3]);
 				copy_m3_m4(hair->rot, root_mat);
-				
+
 				hair->radius = hair_radius;
 				hair->bending_stiffness = bending_stiffness;
-				
-				add_v3_v3v3(mvert->co, co, co);
-				sub_v3_v3(mvert->co, co_next);
+
+				copy_v3_v3(mvert->co, co);
 				mul_m4_v3(hairmat, mvert->co);
-				
-				medge->v1 = pa->hair_index - 1;
-				medge->v2 = pa->hair_index;
-				
-				dvert = hair_set_pinning(dvert, 1.0f);
-				
+
+				if (k) {
+					medge->v1 = pa->hair_index + k - 1;
+					medge->v2 = pa->hair_index + k;
+				}
+
+				/* roots and disabled hairs should be 1.0, the rest can be anything from 0.0 to 1.0 */
+				if (use_hair)
+					dvert = hair_set_pinning(dvert, key->weight);
+				else
+					dvert = hair_set_pinning(dvert, 1.0f);
+
 				mvert++;
-				medge++;
+				if (k)
+					medge++;
 			}
-			
-			/* store root transform in cloth data */
-			hair = &psys->clmd->hairdata[pa->hair_index + k];
-			copy_v3_v3(hair->loc, root_mat[3]);
-			copy_m3_m4(hair->rot, root_mat);
-			
-			hair->radius = hair_radius;
-			hair->bending_stiffness = bending_stiffness;
-			
-			copy_v3_v3(mvert->co, co);
-			mul_m4_v3(hairmat, mvert->co);
-			
-			if (k) {
-				medge->v1 = pa->hair_index + k - 1;
-				medge->v2 = pa->hair_index + k;
-			}
-			
-			/* roots and disabled hairs should be 1.0, the rest can be anything from 0.0 to 1.0 */
-			if (use_hair)
-				dvert = hair_set_pinning(dvert, key->weight);
-			else
-				dvert = hair_set_pinning(dvert, 1.0f);
-			
-			mvert++;
-			if (k)
-				medge++;
+
+			hair_index += pa->totkey + 1;
 		}
-		
-		hair_index += pa->totkey + 1;
 	}
 }
 
@@ -3152,9 +3156,11 @@ static void do_hair_dynamics(ParticleSimulationData *sim)
 	totpoint = 0;
 	totedge = 0;
 	LOOP_PARTICLES {
-		/* "out" dm contains all hairs */
-		totedge += pa->totkey;
-		totpoint += pa->totkey + 1; /* +1 for virtual root point */
+		if (!(pa->flag & PARS_UNEXIST)) {
+			/* "out" dm contains all hairs */
+			totedge += pa->totkey;
+			totpoint += pa->totkey + 1; /* +1 for virtual root point */
+		}
 	}
 	
 	realloc_roots = false; /* whether hair root info array has to be reallocated */