New things for particle effectors:

- For newtonian particles a "self effect" button in particle extras makes the particles be effected by themselves if a particle effector is defined for this system, currently this is a brute force method so things start getting slow with more than ~100 particles, but this will hopefully change in the future.
- Two new effector types: charge and a Lennard-Jones potential based force (inter-molecular forces for example).
   -Charge is similar to spherical field except it changes behavior (attract/repulse) based on the effected particles charge field (negative/positive) like real particles with a charge.
   -The Lennard-Jones field is a very short range force with a behavior determined by the sizes of the effector and effected particle. At a distance smaller than the combined sizes the field is very repulsive and after that distance it's attractive. It tries to keep the particles at an equilibrium distance from each other. Particles need to be at a close proximity to each other to be effected by this field at all.
- Particle systems can now have two effector fields (two slots in the fields panel). This allows to create particles which for example have both a charge and a Lennard-Jones potential.

1 files changed, 43 insertions, 10 deletions

diff --git a/source/blender/blenkernel/intern/effect.c b/source/blender/blenkernel/intern/effect.c
index accc16ea940..0842e55a0ea 100644
--- a/source/blender/blenkernel/intern/effect.c
+++ b/source/blender/blenkernel/intern/effect.c
@@ -332,7 +332,10 @@ float effector_falloff(PartDeflect *pd, float *eff_velocity, float *vec_to_part)
 {
 	float eff_dir[3], temp[3];
 	float falloff=1.0, fac, r_fac;
-	
+
+	if(pd->forcefield==PFIELD_LENNARDJ)
+		return falloff; /* Lennard-Jones field has it's own falloff built in */
+
 	VecCopyf(eff_dir,eff_velocity);
 	Normalize(eff_dir);
 
@@ -369,7 +372,7 @@ float effector_falloff(PartDeflect *pd, float *eff_velocity, float *vec_to_part)
 	return falloff;
 }
 
-void do_physical_effector(Object *ob, float *opco, short type, float force_val, float distance, float falloff, float size, float damp, float *eff_velocity, float *vec_to_part, float *velocity, float *field, int planar, struct RNG *rng, float noise_factor)
+void do_physical_effector(Object *ob, float *opco, short type, float force_val, float distance, float falloff, float size, float damp, float *eff_velocity, float *vec_to_part, float *velocity, float *field, int planar, struct RNG *rng, float noise_factor, float charge, float pa_size)
 {
 	float mag_vec[3]={0,0,0};
 	float temp[3], temp2[3];
@@ -442,14 +445,44 @@ void do_physical_effector(Object *ob, float *opco, short type, float force_val,
 			VecMulf(mag_vec,damp*1.9f*(float)sqrt(force_val));
 			VecSubf(field,field,mag_vec);
 			break;
-		case PFIELD_NUCLEAR:
-			/*pow here is root of cosine expression below*/
-			//rad=(float)pow(2.0,-1.0/power)*distance/size;
-			//VECCOPY(mag_vec,vec_to_part);
-			//Normalize(mag_vec);
-			//VecMulf(mag_vec,(float)cos(3.0*M_PI/2.0*(1.0-1.0/(pow(rad,power)+1.0)))/(rad+0.2f));
-			//VECADDFAC(field,field,mag_vec,force_val);
+		case PFIELD_CHARGE:
+			if(planar)
+				Projf(mag_vec,vec_to_part,eff_vel);
+			else
+				VecCopyf(mag_vec,vec_to_part);
+
+			VecMulf(mag_vec,charge*force_val*falloff);
+			VecAddf(field,field,mag_vec);
+			break;
+		case PFIELD_LENNARDJ:
+		{
+			float fac;
+
+			if(planar) {
+				Projf(mag_vec,vec_to_part,eff_vel);
+				distance = VecLength(mag_vec);
+			}
+			else
+				VecCopyf(mag_vec,vec_to_part);
+
+			/* at this distance the field is 60 times weaker than maximum */
+			if(distance > 2.22 * (size+pa_size))
+				break;
+
+			fac = pow((size+pa_size)/distance,6.0);
+			
+			fac = - fac * (1.0 - fac) / distance;
+
+			/* limit the repulsive term drastically to avoid huge forces */
+			fac = ((fac>2.0) ? 2.0 : fac);
+
+			/* 0.003715 is the fac value at 2.22 times (size+pa_size),
+			   substracted to avoid discontinuity at the border
+			*/
+			VecMulf(mag_vec, force_val * (fac-0.0037315));
+			VecAddf(field,field,mag_vec);
 			break;
+		}
 	}
 }
 
@@ -518,7 +551,7 @@ void pdDoEffectors(ListBase *lb, float *opco, float *force, float *speed, float
 			VECCOPY(field, force);
 			do_physical_effector(ob, opco, pd->forcefield,pd->f_strength,distance,
 								falloff,pd->f_dist,pd->f_damp,ob->obmat[2],vec_to_part,
-								speed,force,pd->flag&PFIELD_PLANAR, pd->rng, pd->f_noise);
+								speed,force,pd->flag&PFIELD_PLANAR, pd->rng, pd->f_noise, 0.0f, 0.0f);
 			
 			// for softbody backward compatibility
 			if(flags & PE_WIND_AS_SPEED){