boids.c

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/* boids.c
 *
 *
 * $Id: boids.c 38285 2011-07-10 17:04:56Z jhk $
 *
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2009 by Janne Karhu.
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): none yet.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include <string.h>
#include <math.h>

#include "MEM_guardedalloc.h"

#include "DNA_object_force.h"
#include "DNA_scene_types.h"

#include "BLI_rand.h"
#include "BLI_math.h"
#include "BLI_blenlib.h"
#include "BLI_kdtree.h"
#include "BLI_utildefines.h"

#include "BKE_collision.h"
#include "BKE_effect.h"
#include "BKE_boids.h"
#include "BKE_particle.h"

#include "BKE_modifier.h"

#include "RNA_enum_types.h"

typedef struct BoidValues {
        float max_speed, max_acc;
        float max_ave, min_speed;
        float personal_space, jump_speed;
} BoidValues;

static int apply_boid_rule(BoidBrainData *bbd, BoidRule *rule, BoidValues *val, ParticleData *pa, float fuzziness);

static int rule_none(BoidRule *UNUSED(rule), BoidBrainData *UNUSED(data), BoidValues *UNUSED(val), ParticleData *UNUSED(pa))
{
        return 0;
}

static int rule_goal_avoid(BoidRule *rule, BoidBrainData *bbd, BoidValues *val, ParticleData *pa)
{
        BoidRuleGoalAvoid *gabr = (BoidRuleGoalAvoid*) rule;
        BoidSettings *boids = bbd->part->boids;
        BoidParticle *bpa = pa->boid;
        EffectedPoint epoint;
        ListBase *effectors = bbd->sim->psys->effectors;
        EffectorCache *cur, *eff = NULL;
        EffectorCache temp_eff;
        EffectorData efd, cur_efd;
        float mul = (rule->type == eBoidRuleType_Avoid ? 1.0 : -1.0);
        float priority = 0.0f, len = 0.0f;
        int ret = 0;

        pd_point_from_particle(bbd->sim, pa, &pa->state, &epoint);

        /* first find out goal/predator with highest priority */
        if(effectors) for(cur = effectors->first; cur; cur=cur->next) {
                Object *eob = cur->ob;
                PartDeflect *pd = cur->pd;

                if(gabr->ob && (rule->type != eBoidRuleType_Goal || gabr->ob != bpa->ground)) {
                        if(gabr->ob == eob) {
                                /* TODO: effectors with multiple points */
                                if(get_effector_data(cur, &efd, &epoint, 0)) {
                                        if(cur->pd && cur->pd->forcefield == PFIELD_BOID)
                                                priority = mul * pd->f_strength * effector_falloff(cur, &efd, &epoint, bbd->part->effector_weights);
                                        else
                                                priority = 1.0;

                                        eff = cur;
                                }
                                break;
                        }
                }
                else if(rule->type == eBoidRuleType_Goal && eob == bpa->ground)
                        ; /* skip current object */
                else if(pd->forcefield == PFIELD_BOID && mul * pd->f_strength > 0.0f && get_effector_data(cur, &cur_efd, &epoint, 0)) {
                        float temp = mul * pd->f_strength * effector_falloff(cur, &cur_efd, &epoint, bbd->part->effector_weights);

                        if(temp == 0.0f)
                                ; /* do nothing */
                        else if(temp > priority) {
                                priority = temp;
                                eff = cur;
                                efd = cur_efd;
                                len = efd.distance;
                        }
                        /* choose closest object with same priority */
                        else if(temp == priority && efd.distance < len) {
                                eff = cur;
                                efd = cur_efd;
                                len = efd.distance;
                        }
                }
        }

        /* if the object doesn't have effector data we have to fake it */
        if(eff == NULL && gabr->ob) {
                memset(&temp_eff, 0, sizeof(EffectorCache));
                temp_eff.ob = gabr->ob;
                temp_eff.scene = bbd->sim->scene;
                eff = &temp_eff;
                get_effector_data(eff, &efd, &epoint, 0);
                priority = 1.0f;
        }

        /* then use that effector */
        if(priority > (rule->type==eBoidRuleType_Avoid ? gabr->fear_factor : 0.0f)) { /* with avoid, factor is "fear factor" */
                Object *eob = eff->ob;
                PartDeflect *pd = eff->pd;
                float surface = (pd && pd->shape == PFIELD_SHAPE_SURFACE) ? 1.0f : 0.0f;

                if(gabr->options & BRULE_GOAL_AVOID_PREDICT) {
                        /* estimate future location of target */
                        get_effector_data(eff, &efd, &epoint, 1);

                        mul_v3_fl(efd.vel, efd.distance / (val->max_speed * bbd->timestep));
                        add_v3_v3(efd.loc, efd.vel);
                        sub_v3_v3v3(efd.vec_to_point, pa->prev_state.co, efd.loc);
                        efd.distance = len_v3(efd.vec_to_point);
                }

                if(rule->type == eBoidRuleType_Goal && boids->options & BOID_ALLOW_CLIMB && surface!=0.0f) {
                        if(!bbd->goal_ob || bbd->goal_priority < priority) {
                                bbd->goal_ob = eob;
                                VECCOPY(bbd->goal_co, efd.loc);
                                VECCOPY(bbd->goal_nor, efd.nor);
                        }
                }
                else if(rule->type == eBoidRuleType_Avoid && bpa->data.mode == eBoidMode_Climbing &&
                        priority > 2.0f * gabr->fear_factor) {
                        /* detach from surface and try to fly away from danger */
                        negate_v3_v3(efd.vec_to_point, bpa->gravity);
                }

                VECCOPY(bbd->wanted_co, efd.vec_to_point);
                mul_v3_fl(bbd->wanted_co, mul);

                bbd->wanted_speed = val->max_speed * priority;

                /* with goals factor is approach velocity factor */
                if(rule->type == eBoidRuleType_Goal && boids->landing_smoothness > 0.0f) {
                        float len2 = 2.0f*len_v3(pa->prev_state.vel);

                        surface *= pa->size * boids->height;

                        if(len2 > 0.0f && efd.distance - surface < len2) {
                                len2 = (efd.distance - surface)/len2;
                                bbd->wanted_speed *= pow(len2, boids->landing_smoothness);
                        }
                }

                ret = 1;
        }

        return ret;
}

static int rule_avoid_collision(BoidRule *rule, BoidBrainData *bbd, BoidValues *val, ParticleData *pa)
{
        BoidRuleAvoidCollision *acbr = (BoidRuleAvoidCollision*) rule;
        KDTreeNearest *ptn = NULL;
        ParticleTarget *pt;
        BoidParticle *bpa = pa->boid;
        ColliderCache *coll;
        float vec[3] = {0.0f, 0.0f, 0.0f}, loc[3] = {0.0f, 0.0f, 0.0f};
        float co1[3], vel1[3], co2[3], vel2[3];
        float  len, t, inp, t_min = 2.0f;
        int n, neighbors = 0, nearest = 0;
        int ret = 0;

        //check deflector objects first
        if(acbr->options & BRULE_ACOLL_WITH_DEFLECTORS && bbd->sim->colliders) {
                ParticleCollision col;
                BVHTreeRayHit hit;
                float radius = val->personal_space * pa->size, ray_dir[3];

                VECCOPY(col.co1, pa->prev_state.co);
                add_v3_v3v3(col.co2, pa->prev_state.co, pa->prev_state.vel);
                sub_v3_v3v3(ray_dir, col.co2, col.co1);
                mul_v3_fl(ray_dir, acbr->look_ahead);
                col.f = 0.0f;
                hit.index = -1;
                hit.dist = col.original_ray_length = len_v3(ray_dir);

                /* find out closest deflector object */
                for(coll = bbd->sim->colliders->first; coll; coll=coll->next) {
                        /* don't check with current ground object */
                        if(coll->ob == bpa->ground)
                                continue;

                        col.current = coll->ob;
                        col.md = coll->collmd;

                        if(col.md && col.md->bvhtree)
                                BLI_bvhtree_ray_cast(col.md->bvhtree, col.co1, ray_dir, radius, &hit, BKE_psys_collision_neartest_cb, &col);
                }
                /* then avoid that object */
                if(hit.index>=0) {
                        t = hit.dist/col.original_ray_length;

                        /* avoid head-on collision */
                        if(dot_v3v3(col.pce.nor, pa->prev_state.ave) < -0.99f) {
                                /* don't know why, but uneven range [0.0,1.0] */
                                /* works much better than even [-1.0,1.0] */
                                bbd->wanted_co[0] = BLI_frand();
                                bbd->wanted_co[1] = BLI_frand();
                                bbd->wanted_co[2] = BLI_frand();
                        }
                        else {
                                copy_v3_v3(bbd->wanted_co, col.pce.nor);
                        }

                        mul_v3_fl(bbd->wanted_co, (1.0f - t) * val->personal_space * pa->size);

                        bbd->wanted_speed = sqrt(t) * len_v3(pa->prev_state.vel);
                        bbd->wanted_speed = MAX2(bbd->wanted_speed, val->min_speed);

                        return 1;
                }
        }

        //check boids in own system
        if(acbr->options & BRULE_ACOLL_WITH_BOIDS)
        {
                neighbors = BLI_kdtree_range_search(bbd->sim->psys->tree, acbr->look_ahead * len_v3(pa->prev_state.vel), pa->prev_state.co, pa->prev_state.ave, &ptn);
                if(neighbors > 1) for(n=1; n<neighbors; n++) {
                        VECCOPY(co1, pa->prev_state.co);
                        VECCOPY(vel1, pa->prev_state.vel);
                        VECCOPY(co2, (bbd->sim->psys->particles + ptn[n].index)->prev_state.co);
                        VECCOPY(vel2, (bbd->sim->psys->particles + ptn[n].index)->prev_state.vel);

                        sub_v3_v3v3(loc, co1, co2);

                        sub_v3_v3v3(vec, vel1, vel2);
                        
                        inp = dot_v3v3(vec,vec);

                        /* velocities not parallel */
                        if(inp != 0.0f) {
                                t = -dot_v3v3(loc, vec)/inp;
                                /* cpa is not too far in the future so investigate further */
                                if(t > 0.0f && t < t_min) {
                                        VECADDFAC(co1, co1, vel1, t);
                                        VECADDFAC(co2, co2, vel2, t);
                                        
                                        sub_v3_v3v3(vec, co2, co1);

                                        len = normalize_v3(vec);

                                        /* distance of cpa is close enough */
                                        if(len < 2.0f * val->personal_space * pa->size) {
                                                t_min = t;

                                                mul_v3_fl(vec, len_v3(vel1));
                                                mul_v3_fl(vec, (2.0f - t)/2.0f);
                                                sub_v3_v3v3(bbd->wanted_co, vel1, vec);
                                                bbd->wanted_speed = len_v3(bbd->wanted_co);
                                                ret = 1;
                                        }
                                }
                        }
                }
        }
        if(ptn){ MEM_freeN(ptn); ptn=NULL; }

        /* check boids in other systems */
        for(pt=bbd->sim->psys->targets.first; pt; pt=pt->next) {
                ParticleSystem *epsys = psys_get_target_system(bbd->sim->ob, pt);

                if(epsys) {
                        neighbors = BLI_kdtree_range_search(epsys->tree, acbr->look_ahead * len_v3(pa->prev_state.vel), pa->prev_state.co, pa->prev_state.ave, &ptn);
                        if(neighbors > 0) for(n=0; n<neighbors; n++) {
                                VECCOPY(co1, pa->prev_state.co);
                                VECCOPY(vel1, pa->prev_state.vel);
                                VECCOPY(co2, (epsys->particles + ptn[n].index)->prev_state.co);
                                VECCOPY(vel2, (epsys->particles + ptn[n].index)->prev_state.vel);

                                sub_v3_v3v3(loc, co1, co2);

                                sub_v3_v3v3(vec, vel1, vel2);
                                
                                inp = dot_v3v3(vec,vec);

                                /* velocities not parallel */
                                if(inp != 0.0f) {
                                        t = -dot_v3v3(loc, vec)/inp;
                                        /* cpa is not too far in the future so investigate further */
                                        if(t > 0.0f && t < t_min) {
                                                VECADDFAC(co1, co1, vel1, t);
                                                VECADDFAC(co2, co2, vel2, t);
                                                
                                                sub_v3_v3v3(vec, co2, co1);

                                                len = normalize_v3(vec);

                                                /* distance of cpa is close enough */
                                                if(len < 2.0f * val->personal_space * pa->size) {
                                                        t_min = t;

                                                        mul_v3_fl(vec, len_v3(vel1));
                                                        mul_v3_fl(vec, (2.0f - t)/2.0f);
                                                        sub_v3_v3v3(bbd->wanted_co, vel1, vec);
                                                        bbd->wanted_speed = len_v3(bbd->wanted_co);
                                                        ret = 1;
                                                }
                                        }
                                }
                        }

                        if(ptn){ MEM_freeN(ptn); ptn=NULL; }
                }
        }


        if(ptn && nearest==0)
                MEM_freeN(ptn);

        return ret;
}
static int rule_separate(BoidRule *UNUSED(rule), BoidBrainData *bbd, BoidValues *val, ParticleData *pa)
{
        KDTreeNearest *ptn = NULL;
        ParticleTarget *pt;
        float len = 2.0f * val->personal_space * pa->size + 1.0f;
        float vec[3] = {0.0f, 0.0f, 0.0f};
        int neighbors = BLI_kdtree_range_search(bbd->sim->psys->tree, 2.0f * val->personal_space * pa->size, pa->prev_state.co, NULL, &ptn);
        int ret = 0;

        if(neighbors > 1 && ptn[1].dist!=0.0f) {
                sub_v3_v3v3(vec, pa->prev_state.co, bbd->sim->psys->particles[ptn[1].index].state.co);
                mul_v3_fl(vec, (2.0f * val->personal_space * pa->size - ptn[1].dist) / ptn[1].dist);
                add_v3_v3(bbd->wanted_co, vec);
                bbd->wanted_speed = val->max_speed;
                len = ptn[1].dist;
                ret = 1;
        }
        if(ptn){ MEM_freeN(ptn); ptn=NULL; }

        /* check other boid systems */
        for(pt=bbd->sim->psys->targets.first; pt; pt=pt->next) {
                ParticleSystem *epsys = psys_get_target_system(bbd->sim->ob, pt);

                if(epsys) {
                        neighbors = BLI_kdtree_range_search(epsys->tree, 2.0f * val->personal_space * pa->size, pa->prev_state.co, NULL, &ptn);
                        
                        if(neighbors > 0 && ptn[0].dist < len) {
                                sub_v3_v3v3(vec, pa->prev_state.co, ptn[0].co);
                                mul_v3_fl(vec, (2.0f * val->personal_space * pa->size - ptn[0].dist) / ptn[1].dist);
                                add_v3_v3(bbd->wanted_co, vec);
                                bbd->wanted_speed = val->max_speed;
                                len = ptn[0].dist;
                                ret = 1;
                        }

                        if(ptn){ MEM_freeN(ptn); ptn=NULL; }
                }
        }
        return ret;
}
static int rule_flock(BoidRule *UNUSED(rule), BoidBrainData *bbd, BoidValues *UNUSED(val), ParticleData *pa)
{
        KDTreeNearest ptn[11];
        float vec[3] = {0.0f, 0.0f, 0.0f}, loc[3] = {0.0f, 0.0f, 0.0f};
        int neighbors = BLI_kdtree_find_n_nearest(bbd->sim->psys->tree, 11, pa->state.co, pa->prev_state.ave, ptn);
        int n;
        int ret = 0;

        if(neighbors > 1) {
                for(n=1; n<neighbors; n++) {
                        add_v3_v3(loc, bbd->sim->psys->particles[ptn[n].index].prev_state.co);
                        add_v3_v3(vec, bbd->sim->psys->particles[ptn[n].index].prev_state.vel);
                }

                mul_v3_fl(loc, 1.0f/((float)neighbors - 1.0f));
                mul_v3_fl(vec, 1.0f/((float)neighbors - 1.0f));

                sub_v3_v3(loc, pa->prev_state.co);
                sub_v3_v3(vec, pa->prev_state.vel);

                add_v3_v3(bbd->wanted_co, vec);
                add_v3_v3(bbd->wanted_co, loc);
                bbd->wanted_speed = len_v3(bbd->wanted_co);

                ret = 1;
        }
        return ret;
}
static int rule_follow_leader(BoidRule *rule, BoidBrainData *bbd, BoidValues *val, ParticleData *pa)
{
        BoidRuleFollowLeader *flbr = (BoidRuleFollowLeader*) rule;
        float vec[3] = {0.0f, 0.0f, 0.0f}, loc[3] = {0.0f, 0.0f, 0.0f};
        float mul, len;
        int n = (flbr->queue_size <= 1) ? bbd->sim->psys->totpart : flbr->queue_size;
        int i, ret = 0, p = pa - bbd->sim->psys->particles;

        if(flbr->ob) {
                float vec2[3], t;

                /* first check we're not blocking the leader*/
                sub_v3_v3v3(vec, flbr->loc, flbr->oloc);
                mul_v3_fl(vec, 1.0f/bbd->timestep);

                sub_v3_v3v3(loc, pa->prev_state.co, flbr->oloc);

                mul = dot_v3v3(vec, vec);

                /* leader is not moving */
                if(mul < 0.01f) {
                        len = len_v3(loc);
                        /* too close to leader */
                        if(len < 2.0f * val->personal_space * pa->size) {
                                VECCOPY(bbd->wanted_co, loc);
                                bbd->wanted_speed = val->max_speed;
                                return 1;
                        }
                }
                else {
                        t = dot_v3v3(loc, vec)/mul;

                        /* possible blocking of leader in near future */
                        if(t > 0.0f && t < 3.0f) {
                                VECCOPY(vec2, vec);
                                mul_v3_fl(vec2, t);

                                sub_v3_v3v3(vec2, loc, vec2);

                                len = len_v3(vec2);

                                if(len < 2.0f * val->personal_space * pa->size) {
                                        VECCOPY(bbd->wanted_co, vec2);
                                        bbd->wanted_speed = val->max_speed * (3.0f - t)/3.0f;
                                        return 1;
                                }
                        }
                }

                /* not blocking so try to follow leader */
                if(p && flbr->options & BRULE_LEADER_IN_LINE) {
                        VECCOPY(vec, bbd->sim->psys->particles[p-1].prev_state.vel);
                        VECCOPY(loc, bbd->sim->psys->particles[p-1].prev_state.co);
                }
                else {
                        VECCOPY(loc, flbr->oloc);
                        sub_v3_v3v3(vec, flbr->loc, flbr->oloc);
                        mul_v3_fl(vec, 1.0f/bbd->timestep);
                }
                
                /* fac is seconds behind leader */
                VECADDFAC(loc, loc, vec, -flbr->distance);

                sub_v3_v3v3(bbd->wanted_co, loc, pa->prev_state.co);
                bbd->wanted_speed = len_v3(bbd->wanted_co);
                        
                ret = 1;
        }
        else if(p % n) {
                float vec2[3], t, t_min = 3.0f;

                /* first check we're not blocking any leaders */
                for(i = 0; i< bbd->sim->psys->totpart; i+=n){
                        VECCOPY(vec, bbd->sim->psys->particles[i].prev_state.vel);

                        sub_v3_v3v3(loc, pa->prev_state.co, bbd->sim->psys->particles[i].prev_state.co);

                        mul = dot_v3v3(vec, vec);

                        /* leader is not moving */
                        if(mul < 0.01f) {
                                len = len_v3(loc);
                                /* too close to leader */
                                if(len < 2.0f * val->personal_space * pa->size) {
                                        VECCOPY(bbd->wanted_co, loc);
                                        bbd->wanted_speed = val->max_speed;
                                        return 1;
                                }
                        }
                        else {
                                t = dot_v3v3(loc, vec)/mul;

                                /* possible blocking of leader in near future */
                                if(t > 0.0f && t < t_min) {
                                        VECCOPY(vec2, vec);
                                        mul_v3_fl(vec2, t);

                                        sub_v3_v3v3(vec2, loc, vec2);

                                        len = len_v3(vec2);

                                        if(len < 2.0f * val->personal_space * pa->size) {
                                                t_min = t;
                                                VECCOPY(bbd->wanted_co, loc);
                                                bbd->wanted_speed = val->max_speed * (3.0f - t)/3.0f;
                                                ret = 1;
                                        }
                                }
                        }
                }

                if(ret) return 1;

                /* not blocking so try to follow leader */
                if(flbr->options & BRULE_LEADER_IN_LINE) {
                        VECCOPY(vec, bbd->sim->psys->particles[p-1].prev_state.vel);
                        VECCOPY(loc, bbd->sim->psys->particles[p-1].prev_state.co);
                }
                else {
                        VECCOPY(vec, bbd->sim->psys->particles[p - p%n].prev_state.vel);
                        VECCOPY(loc, bbd->sim->psys->particles[p - p%n].prev_state.co);
                }
                
                /* fac is seconds behind leader */
                VECADDFAC(loc, loc, vec, -flbr->distance);

                sub_v3_v3v3(bbd->wanted_co, loc, pa->prev_state.co);
                bbd->wanted_speed = len_v3(bbd->wanted_co);
                
                ret = 1;
        }

        return ret;
}
static int rule_average_speed(BoidRule *rule, BoidBrainData *bbd, BoidValues *val, ParticleData *pa)
{
        BoidParticle *bpa = pa->boid;
        BoidRuleAverageSpeed *asbr = (BoidRuleAverageSpeed*)rule;
        float vec[3] = {0.0f, 0.0f, 0.0f};

        if(asbr->wander > 0.0f) {
                /* abuse pa->r_ave for wandering */
                bpa->wander[0] += asbr->wander * (-1.0f + 2.0f * BLI_frand());
                bpa->wander[1] += asbr->wander * (-1.0f + 2.0f * BLI_frand());
                bpa->wander[2] += asbr->wander * (-1.0f + 2.0f * BLI_frand());

                normalize_v3(bpa->wander);

                VECCOPY(vec, bpa->wander);

                mul_qt_v3(pa->prev_state.rot, vec);

                VECCOPY(bbd->wanted_co, pa->prev_state.ave);

                mul_v3_fl(bbd->wanted_co, 1.1f);

                add_v3_v3(bbd->wanted_co, vec);

                /* leveling */
                if(asbr->level > 0.0f && psys_uses_gravity(bbd->sim)) {
                        project_v3_v3v3(vec, bbd->wanted_co, bbd->sim->scene->physics_settings.gravity);
                        mul_v3_fl(vec, asbr->level);
                        sub_v3_v3(bbd->wanted_co, vec);
                }
        }
        else {
                VECCOPY(bbd->wanted_co, pa->prev_state.ave);

                /* may happen at birth */
                if(dot_v2v2(bbd->wanted_co,bbd->wanted_co)==0.0f) {
                        bbd->wanted_co[0] = 2.0f*(0.5f - BLI_frand());
                        bbd->wanted_co[1] = 2.0f*(0.5f - BLI_frand());
                        bbd->wanted_co[2] = 2.0f*(0.5f - BLI_frand());
                }
                
                /* leveling */
                if(asbr->level > 0.0f && psys_uses_gravity(bbd->sim)) {
                        project_v3_v3v3(vec, bbd->wanted_co, bbd->sim->scene->physics_settings.gravity);
                        mul_v3_fl(vec, asbr->level);
                        sub_v3_v3(bbd->wanted_co, vec);
                }

        }
        bbd->wanted_speed = asbr->speed * val->max_speed;
        
        return 1;
}
static int rule_fight(BoidRule *rule, BoidBrainData *bbd, BoidValues *val, ParticleData *pa)
{
        BoidRuleFight *fbr = (BoidRuleFight*)rule;
        KDTreeNearest *ptn = NULL;
        ParticleTarget *pt;
        ParticleData *epars;
        ParticleData *enemy_pa = NULL;
        BoidParticle *bpa;
        /* friends & enemies */
        float closest_enemy[3] = {0.0f,0.0f,0.0f};
        float closest_dist = fbr->distance + 1.0f;
        float f_strength = 0.0f, e_strength = 0.0f;
        float health = 0.0f;
        int n, ret = 0;

        /* calculate own group strength */
        int neighbors = BLI_kdtree_range_search(bbd->sim->psys->tree, fbr->distance, pa->prev_state.co, NULL, &ptn);
        for(n=0; n<neighbors; n++) {
                bpa = bbd->sim->psys->particles[ptn[n].index].boid;
                health += bpa->data.health;
        }

        f_strength += bbd->part->boids->strength * health;

        if(ptn){ MEM_freeN(ptn); ptn=NULL; }

        /* add other friendlies and calculate enemy strength and find closest enemy */
        for(pt=bbd->sim->psys->targets.first; pt; pt=pt->next) {
                ParticleSystem *epsys = psys_get_target_system(bbd->sim->ob, pt);
                if(epsys) {
                        epars = epsys->particles;

                        neighbors = BLI_kdtree_range_search(epsys->tree, fbr->distance, pa->prev_state.co, NULL, &ptn);
                        
                        health = 0.0f;

                        for(n=0; n<neighbors; n++) {
                                bpa = epars[ptn[n].index].boid;
                                health += bpa->data.health;

                                if(n==0 && pt->mode==PTARGET_MODE_ENEMY && ptn[n].dist < closest_dist) {
                                        VECCOPY(closest_enemy, ptn[n].co);
                                        closest_dist = ptn[n].dist;
                                        enemy_pa = epars + ptn[n].index;
                                }
                        }
                        if(pt->mode==PTARGET_MODE_ENEMY)
                                e_strength += epsys->part->boids->strength * health;
                        else if(pt->mode==PTARGET_MODE_FRIEND)
                                f_strength += epsys->part->boids->strength * health;

                        if(ptn){ MEM_freeN(ptn); ptn=NULL; }
                }
        }
        /* decide action if enemy presence found */
        if(e_strength > 0.0f) {
                sub_v3_v3v3(bbd->wanted_co, closest_enemy, pa->prev_state.co);

                /* attack if in range */
                if(closest_dist <= bbd->part->boids->range + pa->size + enemy_pa->size) {
                        float damage = BLI_frand();
                        float enemy_dir[3];

                        normalize_v3_v3(enemy_dir, bbd->wanted_co);

                        /* fight mode */
                        bbd->wanted_speed = 0.0f;

                        /* must face enemy to fight */
                        if(dot_v3v3(pa->prev_state.ave, enemy_dir)>0.5f) {
                                bpa = enemy_pa->boid;
                                bpa->data.health -= bbd->part->boids->strength * bbd->timestep * ((1.0f-bbd->part->boids->accuracy)*damage + bbd->part->boids->accuracy);
                        }
                }
                else {
                        /* approach mode */
                        bbd->wanted_speed = val->max_speed;
                }

                /* check if boid doesn't want to fight */
                bpa = pa->boid;
                if(bpa->data.health/bbd->part->boids->health * bbd->part->boids->aggression < e_strength / f_strength) {
                        /* decide to flee */
                        if(closest_dist < fbr->flee_distance * fbr->distance) {
                                negate_v3(bbd->wanted_co);
                                bbd->wanted_speed = val->max_speed;
                        }
                        else { /* wait for better odds */
                                bbd->wanted_speed = 0.0f;
                        }
                }

                ret = 1;
        }

        return ret;
}

typedef int (*boid_rule_cb)(BoidRule *rule, BoidBrainData *data, BoidValues *val, ParticleData *pa);

static boid_rule_cb boid_rules[] = {
        rule_none,
        rule_goal_avoid,
        rule_goal_avoid,
        rule_avoid_collision,
        rule_separate,
        rule_flock,
        rule_follow_leader,
        rule_average_speed,
        rule_fight,
        //rule_help,
        //rule_protect,
        //rule_hide,
        //rule_follow_path,
        //rule_follow_wall
};

static void set_boid_values(BoidValues *val, BoidSettings *boids, ParticleData *pa)
{
        BoidParticle *bpa = pa->boid;

        if(ELEM(bpa->data.mode, eBoidMode_OnLand, eBoidMode_Climbing)) {
                val->max_speed = boids->land_max_speed * bpa->data.health/boids->health;
                val->max_acc = boids->land_max_acc * val->max_speed;
                val->max_ave = boids->land_max_ave * (float)M_PI * bpa->data.health/boids->health;
                val->min_speed = 0.0f; /* no minimum speed on land */
                val->personal_space = boids->land_personal_space;
                val->jump_speed = boids->land_jump_speed * bpa->data.health/boids->health;
        }
        else {
                val->max_speed = boids->air_max_speed * bpa->data.health/boids->health;
                val->max_acc = boids->air_max_acc * val->max_speed;
                val->max_ave = boids->air_max_ave * (float)M_PI * bpa->data.health/boids->health;
                val->min_speed = boids->air_min_speed * boids->air_max_speed;
                val->personal_space = boids->air_personal_space;
                val->jump_speed = 0.0f; /* no jumping in air */
        }
}

static Object *boid_find_ground(BoidBrainData *bbd, ParticleData *pa, float *ground_co, float *ground_nor)
{
        BoidParticle *bpa = pa->boid;

        if(bpa->data.mode == eBoidMode_Climbing) {
                SurfaceModifierData *surmd = NULL;
                float x[3], v[3];
                
                surmd = (SurfaceModifierData *)modifiers_findByType ( bpa->ground, eModifierType_Surface );

                /* take surface velocity into account */
                closest_point_on_surface(surmd, pa->state.co, x, NULL, v);
                add_v3_v3(x, v);

                /* get actual position on surface */
                closest_point_on_surface(surmd, x, ground_co, ground_nor, NULL);

                return bpa->ground;
        }
        else {
                float zvec[3] = {0.0f, 0.0f, 2000.0f};
                ParticleCollision col;
                ColliderCache *coll;
                BVHTreeRayHit hit;
                float radius = 0.0f, t, ray_dir[3];

                if(!bbd->sim->colliders)
                        return NULL;

                /* first try to find below boid */
                copy_v3_v3(col.co1, pa->state.co);
                sub_v3_v3v3(col.co2, pa->state.co, zvec);
                sub_v3_v3v3(ray_dir, col.co2, col.co1);
                col.f = 0.0f;
                hit.index = -1;
                hit.dist = col.original_ray_length = len_v3(ray_dir);
                col.pce.inside = 0;

                for(coll = bbd->sim->colliders->first; coll; coll = coll->next){
                        col.current = coll->ob;
                        col.md = coll->collmd;
                        col.fac1 = col.fac2 = 0.f;

                        if(col.md && col.md->bvhtree)
                                BLI_bvhtree_ray_cast(col.md->bvhtree, col.co1, ray_dir, radius, &hit, BKE_psys_collision_neartest_cb, &col);
                }
                /* then use that object */
                if(hit.index>=0) {
                        t = hit.dist/col.original_ray_length;
                        interp_v3_v3v3(ground_co, col.co1, col.co2, t);
                        normalize_v3_v3(ground_nor, col.pce.nor);
                        return col.hit;
                }

                /* couldn't find below, so find upmost deflector object */
                add_v3_v3v3(col.co1, pa->state.co, zvec);
                sub_v3_v3v3(col.co2, pa->state.co, zvec);
                sub_v3_v3(col.co2, zvec);
                sub_v3_v3v3(ray_dir, col.co2, col.co1);
                col.f = 0.0f;
                hit.index = -1;
                hit.dist = col.original_ray_length = len_v3(ray_dir);

                for(coll = bbd->sim->colliders->first; coll; coll = coll->next){
                        col.current = coll->ob;
                        col.md = coll->collmd;

                        if(col.md && col.md->bvhtree)
                                BLI_bvhtree_ray_cast(col.md->bvhtree, col.co1, ray_dir, radius, &hit, BKE_psys_collision_neartest_cb, &col);
                }
                /* then use that object */
                if(hit.index>=0) {
                        t = hit.dist/col.original_ray_length;
                        interp_v3_v3v3(ground_co, col.co1, col.co2, t);
                        normalize_v3_v3(ground_nor, col.pce.nor);
                        return col.hit;
                }

                /* default to z=0 */
                VECCOPY(ground_co, pa->state.co);
                ground_co[2] = 0;
                ground_nor[0] = ground_nor[1] = 0.0f;
                ground_nor[2] = 1.0f;
                return NULL;
        }
}
static int boid_rule_applies(ParticleData *pa, BoidSettings *UNUSED(boids), BoidRule *rule)
{
        BoidParticle *bpa = pa->boid;

        if(rule==NULL)
                return 0;
        
        if(ELEM(bpa->data.mode, eBoidMode_OnLand, eBoidMode_Climbing) && rule->flag & BOIDRULE_ON_LAND)
                return 1;
        
        if(bpa->data.mode==eBoidMode_InAir && rule->flag & BOIDRULE_IN_AIR)
                return 1;

        return 0;
}
void boids_precalc_rules(ParticleSettings *part, float cfra)
{
        BoidState *state = part->boids->states.first;
        BoidRule *rule;
        for(; state; state=state->next) {
                for(rule = state->rules.first; rule; rule=rule->next) {
                        if(rule->type==eBoidRuleType_FollowLeader) {
                                BoidRuleFollowLeader *flbr = (BoidRuleFollowLeader*) rule;

                                if(flbr->ob && flbr->cfra != cfra) {
                                        /* save object locations for velocity calculations */
                                        VECCOPY(flbr->oloc, flbr->loc);
                                        VECCOPY(flbr->loc, flbr->ob->obmat[3]);
                                        flbr->cfra = cfra;
                                }
                        }
                }
        }
}
static void boid_climb(BoidSettings *boids, ParticleData *pa, float *surface_co, float *surface_nor)
{
        BoidParticle *bpa = pa->boid;
        float nor[3], vel[3];
        VECCOPY(nor, surface_nor);

        /* gather apparent gravity */
        VECADDFAC(bpa->gravity, bpa->gravity, surface_nor, -1.0f);
        normalize_v3(bpa->gravity);

        /* raise boid it's size from surface */
        mul_v3_fl(nor, pa->size * boids->height);
        add_v3_v3v3(pa->state.co, surface_co, nor);

        /* remove normal component from velocity */
        project_v3_v3v3(vel, pa->state.vel, surface_nor);
        sub_v3_v3v3(pa->state.vel, pa->state.vel, vel);
}
static float boid_goal_signed_dist(float *boid_co, float *goal_co, float *goal_nor)
{
        float vec[3];

        sub_v3_v3v3(vec, boid_co, goal_co);

        return dot_v3v3(vec, goal_nor);
}
/* wanted_co is relative to boid location */
static int apply_boid_rule(BoidBrainData *bbd, BoidRule *rule, BoidValues *val, ParticleData *pa, float fuzziness)
{
        if(rule==NULL)
                return 0;

        if(boid_rule_applies(pa, bbd->part->boids, rule)==0)
                return 0;

        if(boid_rules[rule->type](rule, bbd, val, pa)==0)
                return 0;

        if(fuzziness < 0.0f || compare_len_v3v3(bbd->wanted_co, pa->prev_state.vel, fuzziness * len_v3(pa->prev_state.vel))==0)
                return 1;
        else
                return 0;
}
static BoidState *get_boid_state(BoidSettings *boids, ParticleData *pa) {
        BoidState *state = boids->states.first;
        BoidParticle *bpa = pa->boid;

        for(; state; state=state->next) {
                if(state->id==bpa->data.state_id)
                        return state;
        }

        /* for some reason particle isn't at a valid state */
        state = boids->states.first;
        if(state)
                bpa->data.state_id = state->id;

        return state;
}
//static int boid_condition_is_true(BoidCondition *cond) {
//      /* TODO */
//      return 0;
//}

/* determines the velocity the boid wants to have */
void boid_brain(BoidBrainData *bbd, int p, ParticleData *pa)
{
        BoidRule *rule;
        BoidSettings *boids = bbd->part->boids;
        BoidValues val;
        BoidState *state = get_boid_state(boids, pa);
        BoidParticle *bpa = pa->boid;
        ParticleSystem *psys = bbd->sim->psys;
        int rand;
        //BoidCondition *cond;

        if(bpa->data.health <= 0.0f) {
                pa->alive = PARS_DYING;
                pa->dietime = bbd->cfra;
                return;
        }

        //planned for near future
        //cond = state->conditions.first;
        //for(; cond; cond=cond->next) {
        //      if(boid_condition_is_true(cond)) {
        //              pa->boid->state_id = cond->state_id;
        //              state = get_boid_state(boids, pa);
        //              break; /* only first true condition is used */
        //      }
        //}

        bbd->wanted_co[0]=bbd->wanted_co[1]=bbd->wanted_co[2]=bbd->wanted_speed=0.0f;

        /* create random seed for every particle & frame */
        rand = (int)(PSYS_FRAND(psys->seed + p) * 1000);
        rand = (int)(PSYS_FRAND((int)bbd->cfra + rand) * 1000);

        set_boid_values(&val, bbd->part->boids, pa);

        /* go through rules */
        switch(state->ruleset_type) {
                case eBoidRulesetType_Fuzzy:
                {
                        for(rule = state->rules.first; rule; rule = rule->next) {
                                if(apply_boid_rule(bbd, rule, &val, pa, state->rule_fuzziness))
                                        break; /* only first nonzero rule that comes through fuzzy rule is applied */
                        }
                        break;
                }
                case eBoidRulesetType_Random:
                {
                        /* use random rule for each particle (allways same for same particle though) */
                        rule = BLI_findlink(&state->rules, rand % BLI_countlist(&state->rules));

                        apply_boid_rule(bbd, rule, &val, pa, -1.0);
                }
                case eBoidRulesetType_Average:
                {
                        float wanted_co[3] = {0.0f, 0.0f, 0.0f}, wanted_speed = 0.0f;
                        int n = 0;
                        for(rule = state->rules.first; rule; rule=rule->next) {
                                if(apply_boid_rule(bbd, rule, &val, pa, -1.0f)) {
                                        add_v3_v3(wanted_co, bbd->wanted_co);
                                        wanted_speed += bbd->wanted_speed;
                                        n++;
                                        bbd->wanted_co[0]=bbd->wanted_co[1]=bbd->wanted_co[2]=bbd->wanted_speed=0.0f;
                                }
                        }

                        if(n > 1) {
                                mul_v3_fl(wanted_co, 1.0f/(float)n);
                                wanted_speed /= (float)n;
                        }

                        VECCOPY(bbd->wanted_co, wanted_co);
                        bbd->wanted_speed = wanted_speed;
                        break;
                }

        }

        /* decide on jumping & liftoff */
        if(bpa->data.mode == eBoidMode_OnLand) {
                /* fuzziness makes boids capable of misjudgement */
                float mul = 1.0f + state->rule_fuzziness;
                
                if(boids->options & BOID_ALLOW_FLIGHT && bbd->wanted_co[2] > 0.0f) {
                        float cvel[3], dir[3];

                        VECCOPY(dir, pa->prev_state.ave);
                        normalize_v2(dir);

                        VECCOPY(cvel, bbd->wanted_co);
                        normalize_v2(cvel);

                        if(dot_v2v2(cvel, dir) > 0.95f / mul)
                                bpa->data.mode = eBoidMode_Liftoff;
                }
                else if(val.jump_speed > 0.0f) {
                        float jump_v[3];
                        int jump = 0;

                        /* jump to get to a location */
                        if(bbd->wanted_co[2] > 0.0f) {
                                float cvel[3], dir[3];
                                float z_v, ground_v, cur_v;
                                float len;

                                VECCOPY(dir, pa->prev_state.ave);
                                normalize_v2(dir);

                                VECCOPY(cvel, bbd->wanted_co);
                                normalize_v2(cvel);

                                len = len_v2(pa->prev_state.vel);

                                /* first of all, are we going in a suitable direction? */
                                /* or at a suitably slow speed */
                                if(dot_v2v2(cvel, dir) > 0.95f / mul || len <= state->rule_fuzziness) {
                                        /* try to reach goal at highest point of the parabolic path */
                                        cur_v = len_v2(pa->prev_state.vel);
                                        z_v = sasqrt(-2.0f * bbd->sim->scene->physics_settings.gravity[2] * bbd->wanted_co[2]);
                                        ground_v = len_v2(bbd->wanted_co)*sasqrt(-0.5f * bbd->sim->scene->physics_settings.gravity[2] / bbd->wanted_co[2]);

                                        len = sasqrt((ground_v-cur_v)*(ground_v-cur_v) + z_v*z_v);

                                        if(len < val.jump_speed * mul || bbd->part->boids->options & BOID_ALLOW_FLIGHT) {
                                                jump = 1;

                                                len = MIN2(len, val.jump_speed);

                                                VECCOPY(jump_v, dir);
                                                jump_v[2] = z_v;
                                                mul_v3_fl(jump_v, ground_v);

                                                normalize_v3(jump_v);
                                                mul_v3_fl(jump_v, len);
                                                add_v2_v2v2(jump_v, jump_v, pa->prev_state.vel);
                                        }
                                }
                        }

                        /* jump to go faster */
                        if(jump == 0 && val.jump_speed > val.max_speed && bbd->wanted_speed > val.max_speed) {
                                
                        }

                        if(jump) {
                                VECCOPY(pa->prev_state.vel, jump_v);
                                bpa->data.mode = eBoidMode_Falling;
                        }
                }
        }
}
/* tries to realize the wanted velocity taking all constraints into account */
void boid_body(BoidBrainData *bbd, ParticleData *pa)
{
        BoidSettings *boids = bbd->part->boids;
        BoidParticle *bpa = pa->boid;
        BoidValues val;
        EffectedPoint epoint;
        float acc[3] = {0.0f, 0.0f, 0.0f}, tan_acc[3], nor_acc[3];
        float dvec[3], bvec[3];
        float new_dir[3], new_speed;
        float old_dir[3], old_speed;
        float wanted_dir[3];
        float q[4], mat[3][3]; /* rotation */
        float ground_co[3] = {0.0f, 0.0f, 0.0f}, ground_nor[3] = {0.0f, 0.0f, 1.0f};
        float force[3] = {0.0f, 0.0f, 0.0f};
        float pa_mass=bbd->part->mass, dtime=bbd->dfra*bbd->timestep;

        set_boid_values(&val, boids, pa);

        /* make sure there's something in new velocity, location & rotation */
        copy_particle_key(&pa->state,&pa->prev_state,0);

        if(bbd->part->flag & PART_SIZEMASS)
                pa_mass*=pa->size;

        /* if boids can't fly they fall to the ground */
        if((boids->options & BOID_ALLOW_FLIGHT)==0 && ELEM(bpa->data.mode, eBoidMode_OnLand, eBoidMode_Climbing)==0 && psys_uses_gravity(bbd->sim))
                bpa->data.mode = eBoidMode_Falling;

        if(bpa->data.mode == eBoidMode_Falling) {
                /* Falling boids are only effected by gravity. */
                acc[2] = bbd->sim->scene->physics_settings.gravity[2];
        }
        else {
                /* figure out acceleration */
                float landing_level = 2.0f;
                float level = landing_level + 1.0f;
                float new_vel[3];

                if(bpa->data.mode == eBoidMode_Liftoff) {
                        bpa->data.mode = eBoidMode_InAir;
                        bpa->ground = boid_find_ground(bbd, pa, ground_co, ground_nor);
                }
                else if(bpa->data.mode == eBoidMode_InAir && boids->options & BOID_ALLOW_LAND) {
                        /* auto-leveling & landing if close to ground */

                        bpa->ground = boid_find_ground(bbd, pa, ground_co, ground_nor);
                        
                        /* level = how many particle sizes above ground */
                        level = (pa->prev_state.co[2] - ground_co[2])/(2.0f * pa->size) - 0.5f;

                        landing_level = - boids->landing_smoothness * pa->prev_state.vel[2] * pa_mass;

                        if(pa->prev_state.vel[2] < 0.0f) {
                                if(level < 1.0f) {
                                        bbd->wanted_co[0] = bbd->wanted_co[1] = bbd->wanted_co[2] = 0.0f;
                                        bbd->wanted_speed = 0.0f;
                                        bpa->data.mode = eBoidMode_Falling;
                                }
                                else if(level < landing_level) {
                                        bbd->wanted_speed *= (level - 1.0f)/landing_level;
                                        bbd->wanted_co[2] *= (level - 1.0f)/landing_level;
                                }
                        }
                }

                VECCOPY(old_dir, pa->prev_state.ave);
                new_speed = normalize_v3_v3(wanted_dir, bbd->wanted_co);

                /* first check if we have valid direction we want to go towards */
                if(new_speed == 0.0f) {
                        VECCOPY(new_dir, old_dir);
                }
                else {
                        float old_dir2[2], wanted_dir2[2], nor[3], angle;
                        copy_v2_v2(old_dir2, old_dir);
                        normalize_v2(old_dir2);
                        copy_v2_v2(wanted_dir2, wanted_dir);
                        normalize_v2(wanted_dir2);

                        /* choose random direction to turn if wanted velocity */
                        /* is directly behind regardless of z-coordinate */
                        if(dot_v2v2(old_dir2, wanted_dir2) < -0.99f) {
                                wanted_dir[0] = 2.0f*(0.5f - BLI_frand());
                                wanted_dir[1] = 2.0f*(0.5f - BLI_frand());
                                wanted_dir[2] = 2.0f*(0.5f - BLI_frand());
                                normalize_v3(wanted_dir);
                        }

                        /* constrain direction with maximum angular velocity */
                        angle = saacos(dot_v3v3(old_dir, wanted_dir));
                        angle = MIN2(angle, val.max_ave);

                        cross_v3_v3v3(nor, old_dir, wanted_dir);
                        axis_angle_to_quat( q,nor, angle);
                        VECCOPY(new_dir, old_dir);
                        mul_qt_v3(q, new_dir);
                        normalize_v3(new_dir);

                        /* save direction in case resulting velocity too small */
                        axis_angle_to_quat( q,nor, angle*dtime);
                        VECCOPY(pa->state.ave, old_dir);
                        mul_qt_v3(q, pa->state.ave);
                        normalize_v3(pa->state.ave);
                }

                /* constrain speed with maximum acceleration */
                old_speed = len_v3(pa->prev_state.vel);
                
                if(bbd->wanted_speed < old_speed)
                        new_speed = MAX2(bbd->wanted_speed, old_speed - val.max_acc);
                else
                        new_speed = MIN2(bbd->wanted_speed, old_speed + val.max_acc);

                /* combine direction and speed */
                VECCOPY(new_vel, new_dir);
                mul_v3_fl(new_vel, new_speed);

                /* maintain minimum flying velocity if not landing */
                if(level >= landing_level) {
                        float len2 = dot_v2v2(new_vel,new_vel);
                        float root;

                        len2 = MAX2(len2, val.min_speed*val.min_speed);
                        root = sasqrt(new_speed*new_speed - len2);

                        new_vel[2] = new_vel[2] < 0.0f ? -root : root;

                        normalize_v2(new_vel);
                        mul_v2_fl(new_vel, sasqrt(len2));
                }

                /* finally constrain speed to max speed */
                new_speed = normalize_v3(new_vel);
                mul_v3_fl(new_vel, MIN2(new_speed, val.max_speed));

                /* get acceleration from difference of velocities */
                sub_v3_v3v3(acc, new_vel, pa->prev_state.vel);

                /* break acceleration to components */
                project_v3_v3v3(tan_acc, acc, pa->prev_state.ave);
                sub_v3_v3v3(nor_acc, acc, tan_acc);
        }

        /* account for effectors */
        pd_point_from_particle(bbd->sim, pa, &pa->state, &epoint);
        pdDoEffectors(bbd->sim->psys->effectors, bbd->sim->colliders, bbd->part->effector_weights, &epoint, force, NULL);

        if(ELEM(bpa->data.mode, eBoidMode_OnLand, eBoidMode_Climbing)) {
                float length = normalize_v3(force);

                length = MAX2(0.0f, length - boids->land_stick_force);

                mul_v3_fl(force, length);
        }
        
        add_v3_v3(acc, force);

        /* store smoothed acceleration for nice banking etc. */
        VECADDFAC(bpa->data.acc, bpa->data.acc, acc, dtime);
        mul_v3_fl(bpa->data.acc, 1.0f / (1.0f + dtime));

        /* integrate new location & velocity */

        /* by regarding the acceleration as a force at this stage we*/
        /* can get better control allthough it's a bit unphysical       */
        mul_v3_fl(acc, 1.0f/pa_mass);

        VECCOPY(dvec, acc);
        mul_v3_fl(dvec, dtime*dtime*0.5f);
        
        VECCOPY(bvec, pa->prev_state.vel);
        mul_v3_fl(bvec, dtime);
        add_v3_v3(dvec, bvec);
        add_v3_v3(pa->state.co, dvec);

        VECADDFAC(pa->state.vel, pa->state.vel, acc, dtime);

        //if(bpa->data.mode != eBoidMode_InAir)
        bpa->ground = boid_find_ground(bbd, pa, ground_co, ground_nor);

        /* change modes, constrain movement & keep track of down vector */
        switch(bpa->data.mode) {
                case eBoidMode_InAir:
                {
                        float grav[3];

                        grav[0]= 0.0f;
                        grav[1]= 0.0f;
                        grav[2]= bbd->sim->scene->physics_settings.gravity[2] < 0.0f ? -1.0f : 0.0f;

                        /* don't take forward acceleration into account (better banking) */
                        if(dot_v3v3(bpa->data.acc, pa->state.vel) > 0.0f) {
                                project_v3_v3v3(dvec, bpa->data.acc, pa->state.vel);
                                sub_v3_v3v3(dvec, bpa->data.acc, dvec);
                        }
                        else {
                                VECCOPY(dvec, bpa->data.acc);
                        }

                        /* gather apparent gravity */
                        VECADDFAC(bpa->gravity, grav, dvec, -boids->banking);
                        normalize_v3(bpa->gravity);

                        /* stick boid on goal when close enough */
                        if(bbd->goal_ob && boid_goal_signed_dist(pa->state.co, bbd->goal_co, bbd->goal_nor) <= pa->size * boids->height) {
                                bpa->data.mode = eBoidMode_Climbing;
                                bpa->ground = bbd->goal_ob;
                                boid_find_ground(bbd, pa, ground_co, ground_nor);
                                boid_climb(boids, pa, ground_co, ground_nor);
                        }
                        else if(pa->state.co[2] <= ground_co[2] + pa->size * boids->height) {
                                /* land boid when below ground */
                                if(boids->options & BOID_ALLOW_LAND) {
                                        pa->state.co[2] = ground_co[2] + pa->size * boids->height;
                                        pa->state.vel[2] = 0.0f;
                                        bpa->data.mode = eBoidMode_OnLand;
                                }
                                /* fly above ground */
                                else if(bpa->ground) {
                                        pa->state.co[2] = ground_co[2] + pa->size * boids->height;
                                        pa->state.vel[2] = 0.0f;
                                }
                        }
                        break;
                }
                case eBoidMode_Falling:
                {
                        float grav[3];

                        grav[0]= 0.0f;
                        grav[1]= 0.0f;
                        grav[2]= bbd->sim->scene->physics_settings.gravity[2] < 0.0f ? -1.0f : 0.0f;


                        /* gather apparent gravity */
                        VECADDFAC(bpa->gravity, bpa->gravity, grav, dtime);
                        normalize_v3(bpa->gravity);

                        if(boids->options & BOID_ALLOW_LAND) {
                                /* stick boid on goal when close enough */
                                if(bbd->goal_ob && boid_goal_signed_dist(pa->state.co, bbd->goal_co, bbd->goal_nor) <= pa->size * boids->height) {
                                        bpa->data.mode = eBoidMode_Climbing;
                                        bpa->ground = bbd->goal_ob;
                                        boid_find_ground(bbd, pa, ground_co, ground_nor);
                                        boid_climb(boids, pa, ground_co, ground_nor);
                                }
                                /* land boid when really near ground */
                                else if(pa->state.co[2] <= ground_co[2] + 1.01f * pa->size * boids->height){
                                        pa->state.co[2] = ground_co[2] + pa->size * boids->height;
                                        pa->state.vel[2] = 0.0f;
                                        bpa->data.mode = eBoidMode_OnLand;
                                }
                                /* if we're falling, can fly and want to go upwards lets fly */
                                else if(boids->options & BOID_ALLOW_FLIGHT && bbd->wanted_co[2] > 0.0f)
                                        bpa->data.mode = eBoidMode_InAir;
                        }
                        else
                                bpa->data.mode = eBoidMode_InAir;
                        break;
                }
                case eBoidMode_Climbing:
                {
                        boid_climb(boids, pa, ground_co, ground_nor);
                        //float nor[3];
                        //VECCOPY(nor, ground_nor);

                        //VECADDFAC(pa->r_ve, pa->r_ve, ground_nor, -1.0);
                        //normalize_v3(pa->r_ve);

                        //mul_v3_fl(nor, pa->size * boids->height);
                        //add_v3_v3v3(pa->state.co, ground_co, nor);

                        //project_v3_v3v3(v, pa->state.vel, ground_nor);
                        //sub_v3_v3v3(pa->state.vel, pa->state.vel, v);
                        break;
                }
                case eBoidMode_OnLand:
                {
                        /* stick boid on goal when close enough */
                        if(bbd->goal_ob && boid_goal_signed_dist(pa->state.co, bbd->goal_co, bbd->goal_nor) <= pa->size * boids->height) {
                                bpa->data.mode = eBoidMode_Climbing;
                                bpa->ground = bbd->goal_ob;
                                boid_find_ground(bbd, pa, ground_co, ground_nor);
                                boid_climb(boids, pa, ground_co, ground_nor);
                        }
                        /* ground is too far away so boid falls */
                        else if(pa->state.co[2]-ground_co[2] > 1.1f * pa->size * boids->height)
                                bpa->data.mode = eBoidMode_Falling;
                        else {
                                /* constrain to surface */
                                pa->state.co[2] = ground_co[2] + pa->size * boids->height;
                                pa->state.vel[2] = 0.0f;
                        }

                        if(boids->banking > 0.0f) {
                                float grav[3];
                                /* Don't take gravity's strength in to account, */
                                /* otherwise amount of banking is hard to control. */
                                negate_v3_v3(grav, ground_nor);

                                project_v3_v3v3(dvec, bpa->data.acc, pa->state.vel);
                                sub_v3_v3v3(dvec, bpa->data.acc, dvec);

                                /* gather apparent gravity */
                                VECADDFAC(bpa->gravity, grav, dvec, -boids->banking);
                                normalize_v3(bpa->gravity);
                        }
                        else {
                                /* gather negative surface normal */
                                VECADDFAC(bpa->gravity, bpa->gravity, ground_nor, -1.0f);
                                normalize_v3(bpa->gravity);
                        }
                        break;
                }
        }

        /* save direction to state.ave unless the boid is falling */
        /* (boids can't effect their direction when falling) */
        if(bpa->data.mode!=eBoidMode_Falling && len_v3(pa->state.vel) > 0.1f*pa->size) {
                copy_v3_v3(pa->state.ave, pa->state.vel);
                pa->state.ave[2] *= bbd->part->boids->pitch;
                normalize_v3(pa->state.ave);
        }

        /* apply damping */
        if(ELEM(bpa->data.mode, eBoidMode_OnLand, eBoidMode_Climbing))
                mul_v3_fl(pa->state.vel, 1.0f - 0.2f*bbd->part->dampfac);

        /* calculate rotation matrix based on forward & down vectors */
        if(bpa->data.mode == eBoidMode_InAir) {
                VECCOPY(mat[0], pa->state.ave);

                project_v3_v3v3(dvec, bpa->gravity, pa->state.ave);
                sub_v3_v3v3(mat[2], bpa->gravity, dvec);
                normalize_v3(mat[2]);
        }
        else {
                project_v3_v3v3(dvec, pa->state.ave, bpa->gravity);
                sub_v3_v3v3(mat[0], pa->state.ave, dvec);
                normalize_v3(mat[0]);

                VECCOPY(mat[2], bpa->gravity);
        }
        negate_v3(mat[2]);
        cross_v3_v3v3(mat[1], mat[2], mat[0]);
        
        /* apply rotation */
        mat3_to_quat_is_ok( q,mat);
        copy_qt_qt(pa->state.rot, q);
}

BoidRule *boid_new_rule(int type)
{
        BoidRule *rule = NULL;
        if(type <= 0)
                return NULL;

        switch(type) {
                case eBoidRuleType_Goal:
                case eBoidRuleType_Avoid:
                        rule = MEM_callocN(sizeof(BoidRuleGoalAvoid), "BoidRuleGoalAvoid");
                        break;
                case eBoidRuleType_AvoidCollision:
                        rule = MEM_callocN(sizeof(BoidRuleAvoidCollision), "BoidRuleAvoidCollision");
                        ((BoidRuleAvoidCollision*)rule)->look_ahead = 2.0f;
                        break;
                case eBoidRuleType_FollowLeader:
                        rule = MEM_callocN(sizeof(BoidRuleFollowLeader), "BoidRuleFollowLeader");
                        ((BoidRuleFollowLeader*)rule)->distance = 1.0f;
                        break;
                case eBoidRuleType_AverageSpeed:
                        rule = MEM_callocN(sizeof(BoidRuleAverageSpeed), "BoidRuleAverageSpeed");
                        ((BoidRuleAverageSpeed*)rule)->speed = 0.5f;
                        break;
                case eBoidRuleType_Fight:
                        rule = MEM_callocN(sizeof(BoidRuleFight), "BoidRuleFight");
                        ((BoidRuleFight*)rule)->distance = 100.0f;
                        ((BoidRuleFight*)rule)->flee_distance = 100.0f;
                        break;
                default:
                        rule = MEM_callocN(sizeof(BoidRule), "BoidRule");
                        break;
        }

        rule->type = type;
        rule->flag |= BOIDRULE_IN_AIR|BOIDRULE_ON_LAND;
        BLI_strncpy(rule->name, boidrule_type_items[type-1].name, sizeof(rule->name));

        return rule;
}
void boid_default_settings(BoidSettings *boids)
{
        boids->air_max_speed = 10.0f;
        boids->air_max_acc = 0.5f;
        boids->air_max_ave = 0.5f;
        boids->air_personal_space = 1.0f;

        boids->land_max_speed = 5.0f;
        boids->land_max_acc = 0.5f;
        boids->land_max_ave = 0.5f;
        boids->land_personal_space = 1.0f;

        boids->options = BOID_ALLOW_FLIGHT;

        boids->landing_smoothness = 3.0f;
        boids->banking = 1.0f;
        boids->pitch = 1.0f;
        boids->height = 1.0f;

        boids->health = 1.0f;
        boids->accuracy = 1.0f;
        boids->aggression = 2.0f;
        boids->range = 1.0f;
        boids->strength = 0.1f;
}

BoidState *boid_new_state(BoidSettings *boids)
{
        BoidState *state = MEM_callocN(sizeof(BoidState), "BoidState");

        state->id = boids->last_state_id++;
        if(state->id)
                sprintf(state->name, "State %i", state->id);
        else
                strcpy(state->name, "State");

        state->rule_fuzziness = 0.5;
        state->volume = 1.0f;
        state->channels |= ~0;

        return state;
}

BoidState *boid_duplicate_state(BoidSettings *boids, BoidState *state) {
        BoidState *staten = MEM_dupallocN(state);

        BLI_duplicatelist(&staten->rules, &state->rules);
        BLI_duplicatelist(&staten->conditions, &state->conditions);
        BLI_duplicatelist(&staten->actions, &state->actions);

        staten->id = boids->last_state_id++;

        return staten;
}
void boid_free_settings(BoidSettings *boids)
{
        if(boids) {
                BoidState *state = boids->states.first;

                for(; state; state=state->next) {
                        BLI_freelistN(&state->rules);
                        BLI_freelistN(&state->conditions);
                        BLI_freelistN(&state->actions);
                }

                BLI_freelistN(&boids->states);

                MEM_freeN(boids);
        }
}
BoidSettings *boid_copy_settings(BoidSettings *boids)
{
        BoidSettings *nboids = NULL;

        if(boids) {
                BoidState *state;
                BoidState *nstate;

                nboids = MEM_dupallocN(boids);

                BLI_duplicatelist(&nboids->states, &boids->states);

                state = boids->states.first;
                nstate = nboids->states.first;
                for(; state; state=state->next, nstate=nstate->next) {
                        BLI_duplicatelist(&nstate->rules, &state->rules);
                        BLI_duplicatelist(&nstate->conditions, &state->conditions);
                        BLI_duplicatelist(&nstate->actions, &state->actions);
                }
        }

        return nboids;
}
BoidState *boid_get_current_state(BoidSettings *boids)
{
        BoidState *state = boids->states.first;

        for(; state; state=state->next) {
                if(state->flag & BOIDSTATE_CURRENT)
                        break;
        }

        return state;
}