fix [#35406] Hair puff brush bug

- puff was interpolating hair that made longer strands cirl up.
- also fixed problem with puff-volume option, it was over-accumulating so unselected parts of the hair would have too much offset applied.

1 files changed, 42 insertions, 18 deletions

diff --git a/source/blender/editors/physics/particle_edit.c b/source/blender/editors/physics/particle_edit.c
index f84521fabbf..179195eb344 100644
--- a/source/blender/editors/physics/particle_edit.c
+++ b/source/blender/editors/physics/particle_edit.c
@@ -2963,14 +2963,20 @@ static void brush_puff(PEData *data, int point_index)
 	KEY_K;
 	float mat[4][4], imat[4][4];
 
-	float lastco[3], rootco[3] = {0.0f, 0.0f, 0.0f}, co[3], nor[3], kco[3], dco[3], ofs[3] = {0.0f, 0.0f, 0.0f}, fac=0.0f, length=0.0f;
-	int puff_volume = 0;
-	int change= 0;
+	float onor_prev[3];  /* previous normal (particle-space) */
+	float ofs_prev[3];  /* accumulate offset for puff_volume (particle-space) */
+	float co_root[3], no_root[3];  /* root location and normal (global-space) */
+	float co_prev[3], co[3];  /* track key coords as we loop (global-space) */
+	float fac = 0.0f, length_accum = 0.0f;
+	bool puff_volume = false;
+	bool change = false;
+
+	zero_v3(ofs_prev);
 
 	{
 		ParticleEditSettings *pset= PE_settings(data->scene);
 		ParticleBrushData *brush= &pset->brush[pset->brushtype];
-		puff_volume = brush->flag & PE_BRUSH_DATA_PUFF_VOLUME;
+		puff_volume = (brush->flag & PE_BRUSH_DATA_PUFF_VOLUME) != 0;
 	}
 
 	if (psys && !(psys->flag & PSYS_GLOBAL_HAIR)) {
@@ -2983,6 +2989,8 @@ static void brush_puff(PEData *data, int point_index)
 	}
 
 	LOOP_KEYS {
+		float kco[3];
+
 		if (k==0) {
 			/* find root coordinate and normal on emitter */
 			copy_v3_v3(co, key->co);
@@ -2992,12 +3000,16 @@ static void brush_puff(PEData *data, int point_index)
 			point_index= BLI_kdtree_find_nearest(edit->emitter_field, kco, NULL, NULL);
 			if (point_index == -1) return;
 
-			copy_v3_v3(rootco, co);
-			copy_v3_v3(nor, &edit->emitter_cosnos[point_index*6+3]);
-			mul_mat3_m4_v3(data->ob->obmat, nor); /* normal into worldspace */
+			copy_v3_v3(co_root, co);
+			copy_v3_v3(no_root, &edit->emitter_cosnos[point_index * 6 + 3]);
+			mul_mat3_m4_v3(data->ob->obmat, no_root);  /* normal into global-space */
+			normalize_v3(no_root);
 
-			normalize_v3(nor);
-			length= 0.0f;
+			if (puff_volume) {
+				copy_v3_v3(onor_prev, no_root);
+				mul_mat3_m4_v3(imat, onor_prev); /* global-space into particle space */
+				normalize_v3(onor_prev);
+			}
 
 			fac= (float)pow((double)(1.0f - data->dist / data->rad), (double)data->pufffac);
 			fac *= 0.025f;
@@ -3007,16 +3019,23 @@ static void brush_puff(PEData *data, int point_index)
 		else {
 			/* compute position as if hair was standing up straight.
 			 * */
-			copy_v3_v3(lastco, co);
+			float length;
+			copy_v3_v3(co_prev, co);
 			copy_v3_v3(co, key->co);
 			mul_m4_v3(mat, co);
-			length += len_v3v3(lastco, co);
+			length = len_v3v3(co_prev, co);
+			length_accum += length;
+
 			if ((data->select==0 || (key->flag & PEK_SELECT)) && !(key->flag & PEK_HIDE)) {
-				madd_v3_v3v3fl(kco, rootco, nor, length);
+				float dco[3];  /* delta temp var */
+
+				madd_v3_v3v3fl(kco, co_root, no_root, length_accum);
 
 				/* blend between the current and straight position */
 				sub_v3_v3v3(dco, kco, co);
 				madd_v3_v3fl(co, dco, fac);
+				/* keep the same distance from the root or we get glitches [#35406] */
+				dist_ensure_v3_v3fl(co, co_root, length_accum);
 
 				/* re-use dco to compare before and after translation and add to the offset  */
 				copy_v3_v3(dco, key->co);
@@ -3026,11 +3045,9 @@ static void brush_puff(PEData *data, int point_index)
 				if (puff_volume) {
 					/* accumulate the total distance moved to apply to unselected
 					 * keys that come after */
-					ofs[0] += key->co[0] - dco[0];
-					ofs[1] += key->co[1] - dco[1];
-					ofs[2] += key->co[2] - dco[2];
+					sub_v3_v3v3(ofs_prev, key->co, dco);
 				}
-				change = 1;
+				change = true;
 			}
 			else {
 
@@ -3040,7 +3057,7 @@ static void brush_puff(PEData *data, int point_index)
 					add_v3_v3(key->co, ofs);
 #else
 					/* translate (not rotate) the rest of the hair if its not selected  */
-					if (ofs[0] || ofs[1] || ofs[2]) {
+					{
 #if 0					/* kindof works but looks worse then whats below */
 
 						/* Move the unselected point on a vector based on the
@@ -3070,11 +3087,18 @@ static void brush_puff(PEData *data, int point_index)
 							mul_mat3_m4_v3(data->ob->obmat, onor); /* normal into worldspace */
 							mul_mat3_m4_v3(imat, onor); /* worldspace into particle space */
 							normalize_v3(onor);
+						}
+						else {
+							copy_v3_v3(onor, onor_prev);
+						}
 
+						if (!is_zero_v3(ofs_prev)) {
+							mul_v3_fl(onor, len_v3(ofs_prev));
 
-							mul_v3_fl(onor, len_v3(ofs));
 							add_v3_v3(key->co, onor);
 						}
+
+						copy_v3_v3(onor_prev, onor);
 #endif
 					}
 #endif