static DerivedMesh * applyModifier(ModifierData *md, Object *ob,
						DerivedMesh *derivedData,
						int UNUSED(useRenderParams),
						int UNUSED(isFinalCalc))
{
	DerivedMesh *dm = derivedData, *result;
	ParticleInstanceModifierData *pimd= (ParticleInstanceModifierData*) md;
	ParticleSimulationData sim;
	ParticleSystem *psys= NULL;
	ParticleData *pa= NULL, *pars= NULL;
	MFace *mface, *orig_mface;
	MVert *mvert, *orig_mvert;
	int i,totvert, totpart=0, totface, maxvert, maxface, first_particle=0;
	short track=ob->trackflag%3, trackneg, axis = pimd->axis;
	float max_co=0.0, min_co=0.0, temp_co[3], cross[3];
	float *size=NULL;

	trackneg=((ob->trackflag>2)?1:0);

	if(pimd->ob==ob){
		pimd->ob= NULL;
		return derivedData;
	}

	if(pimd->ob){
		psys = BLI_findlink(&pimd->ob->particlesystem,pimd->psys-1);
		if(psys==NULL || psys->totpart==0)
			return derivedData;
	}
	else return derivedData;

	if(pimd->flag & eParticleInstanceFlag_Parents)
		totpart+=psys->totpart;
	if(pimd->flag & eParticleInstanceFlag_Children){
		if(totpart==0)
			first_particle=psys->totpart;
		totpart+=psys->totchild;
	}

	if(totpart==0)
		return derivedData;

	sim.scene = md->scene;
	sim.ob = pimd->ob;
	sim.psys = psys;
	sim.psmd = psys_get_modifier(pimd->ob, psys);

	if(pimd->flag & eParticleInstanceFlag_UseSize) {
		int p;
		float *si;
		si = size = MEM_callocN(totpart * sizeof(float), "particle size array");

		if(pimd->flag & eParticleInstanceFlag_Parents) {
			for(p=0, pa= psys->particles; p<psys->totpart; p++, pa++, si++)
				*si = pa->size;
		}

		if(pimd->flag & eParticleInstanceFlag_Children) {
			ChildParticle *cpa = psys->child;

			for(p=0; p<psys->totchild; p++, cpa++, si++) {
				*si = psys_get_child_size(psys, cpa, 0.0f, NULL);
			}
		}
	}

	pars=psys->particles;

	totvert=dm->getNumVerts(dm);
	totface=dm->getNumFaces(dm);

	maxvert=totvert*totpart;
	maxface=totface*totpart;

	psys->lattice=psys_get_lattice(&sim);

	if(psys->flag & (PSYS_HAIR_DONE|PSYS_KEYED) || psys->pointcache->flag & PTCACHE_BAKED){

		float min_r[3], max_r[3];
		INIT_MINMAX(min_r, max_r);
		dm->getMinMax(dm, min_r, max_r);
		min_co=min_r[track];
		max_co=max_r[track];
	}

	result = CDDM_from_template(dm, maxvert,dm->getNumEdges(dm)*totpart,maxface);

	mvert=result->getVertArray(result);
	orig_mvert=dm->getVertArray(dm);

	for(i=0; i<maxvert; i++){
		MVert *inMV;
		MVert *mv = mvert + i;
		ParticleKey state;

		inMV = orig_mvert + i%totvert;
		DM_copy_vert_data(dm, result, i%totvert, i, 1);
		*mv = *inMV;

		/*change orientation based on object trackflag*/
		copy_v3_v3(temp_co, mv->co);
		mv->co[axis]=temp_co[track];
		mv->co[(axis+1)%3]=temp_co[(track+1)%3];
		mv->co[(axis+2)%3]=temp_co[(track+2)%3];

		if((psys->flag & (PSYS_HAIR_DONE|PSYS_KEYED) || psys->pointcache->flag & PTCACHE_BAKED) && pimd->flag & eParticleInstanceFlag_Path){
			float ran = 0.0f;
			if(pimd->random_position != 0.0f) {
				BLI_srandom(psys->seed + (i/totvert)%totpart);
				ran = pimd->random_position * BLI_frand();
			}

			if(pimd->flag & eParticleInstanceFlag_KeepShape) {
				state.time = pimd->position * (1.0f - ran);
			}
			else {
				state.time=(mv->co[axis]-min_co)/(max_co-min_co) * pimd->position * (1.0f - ran);

				if(trackneg)
					state.time=1.0f-state.time;

				mv->co[axis] = 0.0;
			}

			psys_get_particle_on_path(&sim, first_particle + i/totvert, &state,1);

			normalize_v3(state.vel);

			/* TODO: incremental rotations somehow */
			if(state.vel[axis] < -0.9999f || state.vel[axis] > 0.9999f) {
				state.rot[0] = 1;
				state.rot[1] = state.rot[2] = state.rot[3] = 0.0f;
			}
			else {
				float temp[3] = {0.0f,0.0f,0.0f};
				temp[axis] = 1.0f;

				cross_v3_v3v3(cross, temp, state.vel);

				/* state.vel[axis] is the only component surviving from a dot product with the axis */
				axis_angle_to_quat(state.rot,cross,saacos(state.vel[axis]));
			}

		}
		else{
			state.time=-1.0;
			psys_get_particle_state(&sim, first_particle + i/totvert, &state,1);
		}

		mul_qt_v3(state.rot,mv->co);
		if(pimd->flag & eParticleInstanceFlag_UseSize)
			mul_v3_fl(mv->co, size[i/totvert]);
		VECADD(mv->co,mv->co,state.co);
	}

	mface=result->getFaceArray(result);
	orig_mface=dm->getFaceArray(dm);

	for(i=0; i<maxface; i++){
		MFace *inMF;
		MFace *mf = mface + i;

		if(pimd->flag & eParticleInstanceFlag_Parents){
			if(i/totface>=psys->totpart){
				if(psys->part->childtype==PART_CHILD_PARTICLES)
					pa=psys->particles+(psys->child+i/totface-psys->totpart)->parent;
				else
					pa= NULL;
			}
			else
				pa=pars+i/totface;
		}
		else{
			if(psys->part->childtype==PART_CHILD_PARTICLES)
				pa=psys->particles+(psys->child+i/totface)->parent;
			else
				pa= NULL;
		}

		if(pa){
			if(pa->alive==PARS_UNBORN && (pimd->flag&eParticleInstanceFlag_Unborn)==0) continue;
			if(pa->alive==PARS_ALIVE && (pimd->flag&eParticleInstanceFlag_Alive)==0) continue;
			if(pa->alive==PARS_DEAD && (pimd->flag&eParticleInstanceFlag_Dead)==0) continue;
		}

		inMF = orig_mface + i%totface;
		DM_copy_face_data(dm, result, i%totface, i, 1);
		*mf = *inMF;

		mf->v1+=(i/totface)*totvert;
		mf->v2+=(i/totface)*totvert;
		mf->v3+=(i/totface)*totvert;
		if(mf->v4)
			mf->v4+=(i/totface)*totvert;
	}

	CDDM_calc_edges(result);
	CDDM_calc_normals(result);

	if(psys->lattice){
		end_latt_deform(psys->lattice);
		psys->lattice= NULL;
	}

	if(size)
		MEM_freeN(size);

	return result;
}
static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
                                  DerivedMesh *derivedData,
                                  ModifierApplyFlag UNUSED(flag))
{
	DerivedMesh *dm = derivedData, *result;
	ParticleInstanceModifierData *pimd = (ParticleInstanceModifierData *) md;
	ParticleSimulationData sim;
	ParticleSystem *psys = NULL;
	ParticleData *pa = NULL;
	MPoly *mpoly, *orig_mpoly;
	MLoop *mloop, *orig_mloop;
	MVert *mvert, *orig_mvert;
	int totvert, totpoly, totloop /* , totedge */;
	int maxvert, maxpoly, maxloop, totpart = 0, first_particle = 0;
	int k, p, p_skip;
	short track = ob->trackflag % 3, trackneg, axis = pimd->axis;
	float max_co = 0.0, min_co = 0.0, temp_co[3];
	float *size = NULL;

	trackneg = ((ob->trackflag > 2) ? 1 : 0);

	if (pimd->ob == ob) {
		pimd->ob = NULL;
		return derivedData;
	}

	if (pimd->ob) {
		psys = BLI_findlink(&pimd->ob->particlesystem, pimd->psys - 1);
		if (psys == NULL || psys->totpart == 0)
			return derivedData;
	}
	else {
		return derivedData;
	}

	if (pimd->flag & eParticleInstanceFlag_Parents)
		totpart += psys->totpart;
	if (pimd->flag & eParticleInstanceFlag_Children) {
		if (totpart == 0)
			first_particle = psys->totpart;
		totpart += psys->totchild;
	}

	if (totpart == 0)
		return derivedData;

	sim.scene = md->scene;
	sim.ob = pimd->ob;
	sim.psys = psys;
	sim.psmd = psys_get_modifier(pimd->ob, psys);

	if (pimd->flag & eParticleInstanceFlag_UseSize) {
		float *si;
		si = size = MEM_callocN(totpart * sizeof(float), "particle size array");

		if (pimd->flag & eParticleInstanceFlag_Parents) {
			for (p = 0, pa = psys->particles; p < psys->totpart; p++, pa++, si++)
				*si = pa->size;
		}

		if (pimd->flag & eParticleInstanceFlag_Children) {
			ChildParticle *cpa = psys->child;

			for (p = 0; p < psys->totchild; p++, cpa++, si++) {
				*si = psys_get_child_size(psys, cpa, 0.0f, NULL);
			}
		}
	}

	totvert = dm->getNumVerts(dm);
	totpoly = dm->getNumPolys(dm);
	totloop = dm->getNumLoops(dm);
	/* totedge = dm->getNumEdges(dm); */ /* UNUSED */

	/* count particles */
	maxvert = 0;
	maxpoly = 0;
	maxloop = 0;

	for (p = 0; p < totpart; p++) {
		if (particle_skip(pimd, psys, p))
			continue;

		maxvert += totvert;
		maxpoly += totpoly;
		maxloop += totloop;
	}

	psys->lattice_deform_data = psys_create_lattice_deform_data(&sim);

	if (psys->flag & (PSYS_HAIR_DONE | PSYS_KEYED) || psys->pointcache->flag & PTCACHE_BAKED) {
		float min[3], max[3];
		INIT_MINMAX(min, max);
		dm->getMinMax(dm, min, max);
		min_co = min[track];
		max_co = max[track];
	}

	result = CDDM_from_template(dm, maxvert, 0, 0, maxloop, maxpoly);

	mvert = result->getVertArray(result);
	orig_mvert = dm->getVertArray(dm);

	mpoly = result->getPolyArray(result);
	orig_mpoly = dm->getPolyArray(dm);
	mloop = result->getLoopArray(result);
	orig_mloop = dm->getLoopArray(dm);

	for (p = 0, p_skip = 0; p < totpart; p++) {
		float prev_dir[3];
		float frame[4]; /* frame orientation quaternion */
		
		/* skip particle? */
		if (particle_skip(pimd, psys, p))
			continue;

		/* set vertices coordinates */
		for (k = 0; k < totvert; k++) {
			ParticleKey state;
			MVert *inMV;
			MVert *mv = mvert + p_skip * totvert + k;

			inMV = orig_mvert + k;
			DM_copy_vert_data(dm, result, k, p_skip * totvert + k, 1);
			*mv = *inMV;

			/*change orientation based on object trackflag*/
			copy_v3_v3(temp_co, mv->co);
			mv->co[axis] = temp_co[track];
			mv->co[(axis + 1) % 3] = temp_co[(track + 1) % 3];
			mv->co[(axis + 2) % 3] = temp_co[(track + 2) % 3];

			/* get particle state */
			if ((psys->flag & (PSYS_HAIR_DONE | PSYS_KEYED) || psys->pointcache->flag & PTCACHE_BAKED) &&
			    (pimd->flag & eParticleInstanceFlag_Path))
			{
				float ran = 0.0f;
				if (pimd->random_position != 0.0f) {
					ran = pimd->random_position * BLI_hash_frand(psys->seed + p);
				}

				if (pimd->flag & eParticleInstanceFlag_KeepShape) {
					state.time = pimd->position * (1.0f - ran);
				}
				else {
					state.time = (mv->co[axis] - min_co) / (max_co - min_co) * pimd->position * (1.0f - ran);

					if (trackneg)
						state.time = 1.0f - state.time;

					mv->co[axis] = 0.0;
				}

				psys_get_particle_on_path(&sim, first_particle + p, &state, 1);

				normalize_v3(state.vel);

				/* Incrementally Rotating Frame (Bishop Frame) */
				if (k == 0) {
					float hairmat[4][4];
					float mat[3][3];
					
					if (first_particle + p < psys->totpart)
						pa = psys->particles + first_particle + p;
					else {
						ChildParticle *cpa = psys->child + (p - psys->totpart);
						pa = psys->particles + cpa->parent;
					}
					psys_mat_hair_to_global(sim.ob, sim.psmd->dm, sim.psys->part->from, pa, hairmat);
					copy_m3_m4(mat, hairmat);
					/* to quaternion */
					mat3_to_quat(frame, mat);
					
					/* note: direction is same as normal vector currently,
					 * but best to keep this separate so the frame can be
					 * rotated later if necessary
					 */
					copy_v3_v3(prev_dir, state.vel);
				}
				else {
					float rot[4];
					
					/* incrementally rotate along bend direction */
					rotation_between_vecs_to_quat(rot, prev_dir, state.vel);
					mul_qt_qtqt(frame, rot, frame);
					
					copy_v3_v3(prev_dir, state.vel);
				}
				
				copy_qt_qt(state.rot, frame);
#if 0
				/* Absolute Frame (Frenet Frame) */
				if (state.vel[axis] < -0.9999f || state.vel[axis] > 0.9999f) {
					unit_qt(state.rot);
				}
				else {
					float cross[3];
					float temp[3] = {0.0f, 0.0f, 0.0f};
					temp[axis] = 1.0f;
					
					cross_v3_v3v3(cross, temp, state.vel);
					
					/* state.vel[axis] is the only component surviving from a dot product with the axis */
					axis_angle_to_quat(state.rot, cross, saacos(state.vel[axis]));
				}
#endif
			}
			else {
				state.time = -1.0;
				psys_get_particle_state(&sim, first_particle + p, &state, 1);
			}

			mul_qt_v3(state.rot, mv->co);
			if (pimd->flag & eParticleInstanceFlag_UseSize)
				mul_v3_fl(mv->co, size[p]);
			add_v3_v3(mv->co, state.co);
		}

		/* create polys and loops */
		for (k = 0; k < totpoly; k++) {
			MPoly *inMP = orig_mpoly + k;
			MPoly *mp = mpoly + p_skip * totpoly + k;

			DM_copy_poly_data(dm, result, k, p_skip * totpoly + k, 1);
			*mp = *inMP;
			mp->loopstart += p_skip * totloop;

			{
				MLoop *inML = orig_mloop + inMP->loopstart;
				MLoop *ml = mloop + mp->loopstart;
				int j = mp->totloop;

				DM_copy_loop_data(dm, result, inMP->loopstart, mp->loopstart, j);
				for (; j; j--, ml++, inML++) {
					ml->v = inML->v + (p_skip * totvert);
				}
			}
		}

		p_skip++;
	}

	CDDM_calc_edges(result);

	if (psys->lattice_deform_data) {
		end_latt_deform(psys->lattice_deform_data);
		psys->lattice_deform_data = NULL;
	}

	if (size)
		MEM_freeN(size);

	result->dirty |= DM_DIRTY_NORMALS;

	return result;
}