/**
* For a hit on the surface of an METABALL, return the (u, v)
* coordinates of the hit point, 0 <= u, v <= 1.
*
* u = azimuth
* v = elevation
*/
void
rt_metaball_uv(struct application *ap, struct soltab *stp, struct hit *hitp, struct uvcoord *uvp)
{
struct rt_metaball_internal *metaball = (struct rt_metaball_internal *)stp->st_specific;
vect_t work, pprime;
fastf_t r;
if (ap) RT_CK_APPLICATION(ap);
if (stp) RT_CK_SOLTAB(stp);
if (hitp) RT_CK_HIT(hitp);
if (!uvp) return;
if (!metaball) return;
/* stuff stolen from sph */
VSUB2(work, hitp->hit_point, stp->st_center);
VSCALE(pprime, work, 1.0/MAGNITUDE(work));
/* Assert that pprime has unit length */
/* U is azimuth, atan() range: -pi to +pi */
uvp->uv_u = bn_atan2(pprime[Y], pprime[X]) * M_1_2PI;
if (uvp->uv_u < 0)
uvp->uv_u += 1.0;
/*
* V is elevation, atan() range: -pi/2 to +pi/2, because sqrt()
* ensures that X parameter is always >0
*/
uvp->uv_v = bn_atan2(pprime[Z],
sqrt(pprime[X] * pprime[X] + pprime[Y] * pprime[Y])) * M_1_2PI;
/* approximation: r / (circumference, 2 * pi * aradius) */
r = ap->a_rbeam + ap->a_diverge * hitp->hit_dist;
uvp->uv_du = uvp->uv_dv =
M_1_2PI * r / stp->st_aradius;
return;
}
void
bn_ae_vec(fastf_t *azp, fastf_t *elp, const vect_t v)
{
register fastf_t az;
if ((az = bn_atan2(v[Y], v[X]) * RAD2DEG) < 0) {
*azp = 360 + az;
} else if (az >= 360) {
*azp = az - 360;
} else {
*azp = az;
}
*elp = bn_atan2(v[Z], hypot(v[X], v[Y])) * RAD2DEG;
}
void
bn_aet_vec(
fastf_t *az,
fastf_t *el,
fastf_t *twist,
fastf_t *vec_ae,
fastf_t *vec_twist,
fastf_t accuracy)
{
vect_t zero_twist, ninety_twist;
vect_t z_dir;
/* Get az and el as usual */
bn_ae_vec(az, el, vec_ae);
/* stabilize fluctuation between 0 and 360
* change azimuth near 360 to 0 */
if (NEAR_EQUAL(*az, 360.0, accuracy)) {
*az = 0.0;
}
/* if elevation is +/-90 set twist to zero and calculate azimuth */
if (NEAR_EQUAL(*el, 90.0, accuracy) || NEAR_ZERO(*el + 90.0, accuracy)) {
*twist = 0.0;
*az = bn_atan2(-vec_twist[X], vec_twist[Y]) * RAD2DEG;
} else {
/* Calculate twist from vec_twist */
VSET(z_dir, 0, 0, 1);
VCROSS(zero_twist, z_dir, vec_ae);
VUNITIZE(zero_twist);
VCROSS(ninety_twist, vec_ae, zero_twist);
VUNITIZE(ninety_twist);
*twist = bn_atan2(VDOT(vec_twist, ninety_twist), VDOT(vec_twist, zero_twist)) * RAD2DEG;
/* stabilize flutter between +/- 180 */
if (NEAR_EQUAL(*twist, -180.0, accuracy)) {
*twist = 180.0;
}
}
}
static int
test_bn_atan2(int argc, char *argv[])
{
double x, y, expected, actual;
if (argc != 5) {
bu_exit(1, "<args> format: X Y <expected_result> [%s]\n", argv[0]);
}
sscanf(argv[2], "%lg", &y);
sscanf(argv[3], "%lg", &x);
sscanf(argv[4], "%lg", &expected);
actual = bn_atan2(y, x);
return !NEAR_EQUAL(expected, actual, 0.00001);
}
