/**
* prep and build bounding volumes... unfortunately, generating the
* bounding sphere is too 'loose' (I think) and O(n^2).
*/
int
rt_metaball_prep(struct soltab *stp, struct rt_db_internal *ip, struct rt_i *rtip)
{
struct rt_metaball_internal *mb, *nmb;
struct wdb_metaballpt *mbpt, *nmbpt;
fastf_t minfstr = +INFINITY;
if (rtip) RT_CK_RTI(rtip);
mb = (struct rt_metaball_internal *)ip->idb_ptr;
RT_METABALL_CK_MAGIC(mb);
/* generate a copy of the metaball */
BU_ALLOC(nmb, struct rt_metaball_internal);
nmb->magic = RT_METABALL_INTERNAL_MAGIC;
BU_LIST_INIT(&nmb->metaball_ctrl_head);
nmb->threshold = mb->threshold;
nmb->method = mb->method;
/* and copy the list of control points */
for (BU_LIST_FOR(mbpt, wdb_metaballpt, &mb->metaball_ctrl_head)) {
BU_ALLOC(nmbpt, struct wdb_metaballpt);
nmbpt->fldstr = mbpt->fldstr;
if (mbpt->fldstr < minfstr)
minfstr = mbpt->fldstr;
nmbpt->sweat = mbpt->sweat;
VMOVE(nmbpt->coord, mbpt->coord);
BU_LIST_INSERT(&nmb->metaball_ctrl_head, &nmbpt->l);
}
/* find the bounding sphere */
stp->st_aradius = rt_metaball_get_bounding_sphere(&stp->st_center, mb->threshold, mb);
stp->st_bradius = stp->st_aradius * 1.01;
/* XXX magic numbers, increase if scalloping is observed. :(*/
nmb->initstep = minfstr / 2.0;
if (nmb->initstep < (stp->st_aradius / 200.0))
nmb->initstep = (stp->st_aradius / 200.0);
else if (nmb->initstep > (stp->st_aradius / 10.0))
nmb->initstep = (stp->st_aradius / 10.0);
nmb->finalstep = /*stp->st_aradius * */minfstr / 1e5;
/* generate a bounding box around the sphere...
* XXX this can be optimized greatly to reduce the BSP presence... */
if (rt_metaball_bbox(ip, &(stp->st_min), &(stp->st_max), &rtip->rti_tol)) return 1;
stp->st_specific = (void *)nmb;
return 0;
}
/**
* R T _ M E T A B A L L _ T E S S
*
* Tessellate a metaball.
*/
int
rt_metaball_tess(struct nmgregion **r, struct model *m, struct rt_db_internal *ip, const struct rt_tess_tol *ttol, const struct bn_tol *tol)
{
struct rt_metaball_internal *mb;
fastf_t mtol, radius;
point_t center, min, max;
fastf_t i, j, k, finalstep = +INFINITY;
struct bu_vls times = BU_VLS_INIT_ZERO;
struct wdb_metaballpt *mbpt;
struct shell *s;
int numtri = 0;
if (r == NULL || m == NULL)
return -1;
*r = NULL;
NMG_CK_MODEL(m);
RT_CK_DB_INTERNAL(ip);
mb = (struct rt_metaball_internal *)ip->idb_ptr;
RT_METABALL_CK_MAGIC(mb);
rt_prep_timer();
/* since this geometry isn't necessarily prepped, we have to figure out the
* finalstep and bounding box manually. */
for (BU_LIST_FOR(mbpt, wdb_metaballpt, &mb->metaball_ctrl_head))
V_MIN(finalstep, mbpt->fldstr);
finalstep /= (fastf_t)1e5;
radius = rt_metaball_get_bounding_sphere(¢er, mb->threshold, mb);
if(radius < 0) { /* no control points */
bu_log("Attempting to tesselate metaball with no control points");
return -1;
}
rt_metaball_bbox(ip, &min, &max, tol);
/* TODO: get better sampling tolerance, unless this is "good enough" */
mtol = ttol->abs;
V_MAX(mtol, ttol->rel * radius * 10);
V_MAX(mtol, tol->dist);
*r = nmg_mrsv(m); /* new empty nmg */
s = BU_LIST_FIRST(shell, &(*r)->s_hd);
/* the incredibly naïve approach. Time could be cut in half by simply
* caching 4 point values, more by actually marching or doing active
* refinement. This is the simplest pattern for now.
*/
for (i = min[X]; i < max[X]; i += mtol)
for (j = min[Y]; j < max[Y]; j += mtol)
for (k = min[Z]; k < max[Z]; k += mtol) {
point_t p[8];
int pv = 0;
/* generate the vertex values */
#define MEH(c,di,dj,dk) VSET(p[c], i+di, j+dj, k+dk); pv |= rt_metaball_point_inside((const point_t *)&p[c], mb) << c;
MEH(0, 0, 0, mtol);
MEH(1, mtol, 0, mtol);
MEH(2, mtol, 0, 0);
MEH(3, 0, 0, 0);
MEH(4, 0, mtol, mtol);
MEH(5, mtol, mtol, mtol);
MEH(6, mtol, mtol, 0);
MEH(7, 0, mtol, 0);
#undef MEH
if ( pv != 0 && pv != 255 ) { /* entire cube is either inside or outside */
point_t edges[12];
int rval;
/* compute the edge values (if needed) */
#define MEH(a,b,c) if(!(pv&(1<<b)&&pv&(1<<c))) { \
rt_metaball_find_intersection(edges+a, mb, (const point_t *)(p+b), (const point_t *)(p+c), mtol, finalstep); \
}
/* magic numbers! an edge, then the two attached vertices.
* For edge/vertex mapping, refer to the awesome ascii art
* at the beginning of this file. */
MEH(0 ,0,1);
MEH(1 ,1,2);
MEH(2 ,2,3);
MEH(3 ,0,3);
MEH(4 ,4,5);
MEH(5 ,5,6);
MEH(6 ,6,7);
MEH(7 ,4,7);
MEH(8 ,0,4);
MEH(9 ,1,5);
MEH(10,2,6);
MEH(11,3,7);
#undef MEH
rval = nmg_mc_realize_cube(s, pv, (point_t *)edges, tol);
numtri += rval;
if(rval < 0) {
bu_log("Error attempting to realize a cube O.o\n");
return rval;
}
}
}
nmg_mark_edges_real(&s->l.magic);
nmg_region_a(*r, tol);
nmg_model_fuse(m, tol);
rt_get_timer(×, NULL);
bu_log("metaball tesselate (%d triangles): %s\n", numtri, bu_vls_addr(×));
return 0;
}
