Small particle effectors update:

* Greetings from farsthary: particle rotation is now taken into account for particle effector direction.
** This gives all kinds of new possibilities as he shows in his blog http://farsthary.wordpress.com/2011/02/08/vortex-particle-simple-tut/.
**The only modification I made to his patch was to use the actual rotated particle direction as the effector direction as this defaults to the particle velocity vector, so no actual new options are needed.
* I also added an "effector amount" setting for particle effectors so that only a part of the particles can be considered as effectors. This makes it possible to create simple "farsthary vortexes" with only one particle system.
* Also some tiny reorganization of the falloff min/max values for a nicer ui.

1 files changed, 20 insertions, 9 deletions

diff --git a/source/blender/blenkernel/intern/effect.c b/source/blender/blenkernel/intern/effect.c
index a79a5fddf00..43ca7435712 100644
--- a/source/blender/blenkernel/intern/effect.c
+++ b/source/blender/blenkernel/intern/effect.c
@@ -651,11 +651,15 @@ int get_effector_data(EffectorCache *eff, EffectorData *efd, EffectedPoint *poin
 			//		eff->flag |= PE_VELOCITY_TO_IMPULSE;
 			//}
 
-			VECCOPY(efd->loc, state.co);
-			VECCOPY(efd->nor, state.vel);
-			if(real_velocity) {
-				VECCOPY(efd->vel, state.vel);
-			}
+			copy_v3_v3(efd->loc, state.co);
+
+			/* rather than use the velocity use rotated x-axis (defaults to velocity) */
+			efd->nor[0] = 1.f;
+			efd->nor[1] = efd->nor[2] = 0.f;
+			mul_qt_v3(state.rot, efd->nor);
+		
+			if(real_velocity)
+				copy_v3_v3(efd->vel, state.vel);
 
 			efd->size = pa->size;
 		}
@@ -720,7 +724,7 @@ int get_effector_data(EffectorCache *eff, EffectorData *efd, EffectedPoint *poin
 
 	return ret;
 }
-static void get_effector_tot(EffectorCache *eff, EffectorData *efd, EffectedPoint *point, int *tot, int *p)
+static void get_effector_tot(EffectorCache *eff, EffectorData *efd, EffectedPoint *point, int *tot, int *p, int *step)
 {
 	if(eff->pd->shape == PFIELD_SHAPE_POINTS) {
 		efd->index = p;
@@ -753,6 +757,13 @@ static void get_effector_tot(EffectorCache *eff, EffectorData *efd, EffectedPoin
 			*p= point->index % eff->psys->totpart;
 			*tot= *p + 1;
 		}
+
+		if(eff->psys->part->effector_amount) {
+			int totpart = eff->psys->totpart;
+			int amount = eff->psys->part->effector_amount;
+
+			*step = (totpart > amount) ? totpart/amount : 1;
+		}
 	}
 	else {
 		*p = 0;
@@ -990,7 +1001,7 @@ void pdDoEffectors(ListBase *effectors, ListBase *colliders, EffectorWeights *we
 */
 	EffectorCache *eff;
 	EffectorData efd;
-	int p=0, tot = 1;
+	int p=0, tot = 1, step = 1;
 
 	/* Cycle through collected objects, get total of (1/(gravity_strength * dist^gravity_power)) */
 	/* Check for min distance here? (yes would be cool to add that, ton) */
@@ -998,9 +1009,9 @@ void pdDoEffectors(ListBase *effectors, ListBase *colliders, EffectorWeights *we
 	if(effectors) for(eff = effectors->first; eff; eff=eff->next) {
 		/* object effectors were fully checked to be OK to evaluate! */
 
-		get_effector_tot(eff, &efd, point, &tot, &p);
+		get_effector_tot(eff, &efd, point, &tot, &p, &step);
 
-		for(; p<tot; p++) {
+		for(; p<tot; p+=step) {
 			if(get_effector_data(eff, &efd, point, 0)) {
 				efd.falloff= effector_falloff(eff, &efd, point, weights);