BLI_INLINE void cloth_calc_spring_force(ClothModifierData *clmd, ClothSpring *s, float time)
{
Cloth *cloth = clmd->clothObject;
ClothSimSettings *parms = clmd->sim_parms;
Implicit_Data *data = cloth->implicit;
ClothVertex *verts = cloth->verts;
bool no_compress = parms->flags & CLOTH_SIMSETTINGS_FLAG_NO_SPRING_COMPRESS;
zero_v3(s->f);
zero_m3(s->dfdx);
zero_m3(s->dfdv);
s->flags &= ~CLOTH_SPRING_FLAG_NEEDED;
// calculate force of structural + shear springs
if ((s->type & CLOTH_SPRING_TYPE_STRUCTURAL) || (s->type & CLOTH_SPRING_TYPE_SHEAR) || (s->type & CLOTH_SPRING_TYPE_SEWING) ) {
#ifdef CLOTH_FORCE_SPRING_STRUCTURAL
float k, scaling;
s->flags |= CLOTH_SPRING_FLAG_NEEDED;
scaling = parms->structural + s->stiffness * fabsf(parms->max_struct - parms->structural);
k = scaling / (parms->avg_spring_len + FLT_EPSILON);
if (s->type & CLOTH_SPRING_TYPE_SEWING) {
// TODO: verify, half verified (couldn't see error)
// sewing springs usually have a large distance at first so clamp the force so we don't get tunnelling through colission objects
BPH_mass_spring_force_spring_linear(data, s->ij, s->kl, s->restlen, k, parms->Cdis, no_compress, parms->max_sewing, s->f, s->dfdx, s->dfdv);
}
else {
BPH_mass_spring_force_spring_linear(data, s->ij, s->kl, s->restlen, k, parms->Cdis, no_compress, 0.0f, s->f, s->dfdx, s->dfdv);
}
#endif
}
else if (s->type & CLOTH_SPRING_TYPE_GOAL) {
#ifdef CLOTH_FORCE_SPRING_GOAL
float goal_x[3], goal_v[3];
float k, scaling;
s->flags |= CLOTH_SPRING_FLAG_NEEDED;
// current_position = xold + t * (newposition - xold)
/* divide by time_scale to prevent goal vertices' delta locations from being multiplied */
interp_v3_v3v3(goal_x, verts[s->ij].xold, verts[s->ij].xconst, time / parms->time_scale);
sub_v3_v3v3(goal_v, verts[s->ij].xconst, verts[s->ij].xold); // distance covered over dt==1
scaling = parms->goalspring + s->stiffness * fabsf(parms->max_struct - parms->goalspring);
k = verts[s->ij].goal * scaling / (parms->avg_spring_len + FLT_EPSILON);
BPH_mass_spring_force_spring_goal(data, s->ij, goal_x, goal_v, k, parms->goalfrict * 0.01f, s->f, s->dfdx, s->dfdv);
#endif
}
else if (s->type & CLOTH_SPRING_TYPE_BENDING) { /* calculate force of bending springs */
#ifdef CLOTH_FORCE_SPRING_BEND
float kb, cb, scaling;
s->flags |= CLOTH_SPRING_FLAG_NEEDED;
scaling = parms->bending + s->stiffness * fabsf(parms->max_bend - parms->bending);
kb = scaling / (20.0f * (parms->avg_spring_len + FLT_EPSILON));
// Fix for [#45084] for cloth stiffness must have cb proportional to kb
cb = kb * parms->bending_damping;
BPH_mass_spring_force_spring_bending(data, s->ij, s->kl, s->restlen, kb, cb, s->f, s->dfdx, s->dfdv);
#endif
}
else if (s->type & CLOTH_SPRING_TYPE_BENDING_ANG) {
#ifdef CLOTH_FORCE_SPRING_BEND
float kb, cb, scaling;
s->flags |= CLOTH_SPRING_FLAG_NEEDED;
/* XXX WARNING: angular bending springs for hair apply stiffness factor as an overall factor, unlike cloth springs!
* this is crap, but needed due to cloth/hair mixing ...
* max_bend factor is not even used for hair, so ...
*/
scaling = s->stiffness * parms->bending;
kb = scaling / (20.0f * (parms->avg_spring_len + FLT_EPSILON));
// Fix for [#45084] for cloth stiffness must have cb proportional to kb
cb = kb * parms->bending_damping;
/* XXX assuming same restlen for ij and jk segments here, this can be done correctly for hair later */
BPH_mass_spring_force_spring_bending_angular(data, s->ij, s->kl, s->mn, s->target, kb, cb);
#if 0
{
float x_kl[3], x_mn[3], v[3], d[3];
BPH_mass_spring_get_motion_state(data, s->kl, x_kl, v);
BPH_mass_spring_get_motion_state(data, s->mn, x_mn, v);
BKE_sim_debug_data_add_dot(clmd->debug_data, x_kl, 0.9, 0.9, 0.9, "target", 7980, s->kl);
BKE_sim_debug_data_add_line(clmd->debug_data, x_kl, x_mn, 0.8, 0.8, 0.8, "target", 7981, s->kl);
copy_v3_v3(d, s->target);
BKE_sim_debug_data_add_vector(clmd->debug_data, x_kl, d, 0.8, 0.8, 0.2, "target", 7982, s->kl);
// copy_v3_v3(d, s->target_ij);
// BKE_sim_debug_data_add_vector(clmd->debug_data, x, d, 1, 0.4, 0.4, "target", 7983, s->kl);
}
#endif
#endif
}
}
static void cloth_continuum_step(ClothModifierData *clmd, float dt)
{
ClothSimSettings *parms = clmd->sim_parms;
Cloth *cloth = clmd->clothObject;
Implicit_Data *data = cloth->implicit;
int mvert_num = cloth->mvert_num;
ClothVertex *vert;
const float fluid_factor = 0.95f; /* blend between PIC and FLIP methods */
float smoothfac = parms->velocity_smooth;
/* XXX FIXME arbitrary factor!!! this should be based on some intuitive value instead,
* like number of hairs per cell and time decay instead of "strength"
*/
float density_target = parms->density_target;
float density_strength = parms->density_strength;
float gmin[3], gmax[3];
int i;
/* clear grid info */
zero_v3_int(clmd->hair_grid_res);
zero_v3(clmd->hair_grid_min);
zero_v3(clmd->hair_grid_max);
clmd->hair_grid_cellsize = 0.0f;
hair_get_boundbox(clmd, gmin, gmax);
/* gather velocities & density */
if (smoothfac > 0.0f || density_strength > 0.0f) {
HairGrid *grid = BPH_hair_volume_create_vertex_grid(clmd->sim_parms->voxel_cell_size, gmin, gmax);
cloth_continuum_fill_grid(grid, cloth);
/* main hair continuum solver */
BPH_hair_volume_solve_divergence(grid, dt, density_target, density_strength);
for (i = 0, vert = cloth->verts; i < mvert_num; i++, vert++) {
float x[3], v[3], nv[3];
/* calculate volumetric velocity influence */
BPH_mass_spring_get_position(data, i, x);
BPH_mass_spring_get_new_velocity(data, i, v);
BPH_hair_volume_grid_velocity(grid, x, v, fluid_factor, nv);
interp_v3_v3v3(nv, v, nv, smoothfac);
/* apply on hair data */
BPH_mass_spring_set_new_velocity(data, i, nv);
}
/* store basic grid info in the modifier data */
BPH_hair_volume_grid_geometry(grid, &clmd->hair_grid_cellsize, clmd->hair_grid_res, clmd->hair_grid_min, clmd->hair_grid_max);
#if 0 /* DEBUG hair velocity vector field */
{
const int size = 64;
int i, j;
float offset[3], a[3], b[3];
const int axis = 0;
const float shift = 0.0f;
copy_v3_v3(offset, clmd->hair_grid_min);
zero_v3(a);
zero_v3(b);
offset[axis] = shift * clmd->hair_grid_cellsize;
a[(axis+1) % 3] = clmd->hair_grid_max[(axis+1) % 3] - clmd->hair_grid_min[(axis+1) % 3];
b[(axis+2) % 3] = clmd->hair_grid_max[(axis+2) % 3] - clmd->hair_grid_min[(axis+2) % 3];
BKE_sim_debug_data_clear_category(clmd->debug_data, "grid velocity");
for (j = 0; j < size; ++j) {
for (i = 0; i < size; ++i) {
float x[3], v[3], gvel[3], gvel_smooth[3], gdensity;
madd_v3_v3v3fl(x, offset, a, (float)i / (float)(size-1));
madd_v3_v3fl(x, b, (float)j / (float)(size-1));
zero_v3(v);
BPH_hair_volume_grid_interpolate(grid, x, &gdensity, gvel, gvel_smooth, NULL, NULL);
// BKE_sim_debug_data_add_circle(clmd->debug_data, x, gdensity, 0.7, 0.3, 1, "grid density", i, j, 3111);
if (!is_zero_v3(gvel) || !is_zero_v3(gvel_smooth)) {
float dvel[3];
sub_v3_v3v3(dvel, gvel_smooth, gvel);
// BKE_sim_debug_data_add_vector(clmd->debug_data, x, gvel, 0.4, 0, 1, "grid velocity", i, j, 3112);
// BKE_sim_debug_data_add_vector(clmd->debug_data, x, gvel_smooth, 0.6, 1, 1, "grid velocity", i, j, 3113);
BKE_sim_debug_data_add_vector(clmd->debug_data, x, dvel, 0.4, 1, 0.7, "grid velocity", i, j, 3114);
#if 0
if (gdensity > 0.0f) {
float col0[3] = {0.0, 0.0, 0.0};
float col1[3] = {0.0, 1.0, 0.0};
float col[3];
interp_v3_v3v3(col, col0, col1, CLAMPIS(gdensity * clmd->sim_parms->density_strength, 0.0, 1.0));
// BKE_sim_debug_data_add_circle(clmd->debug_data, x, gdensity * clmd->sim_parms->density_strength, 0, 1, 0.4, "grid velocity", i, j, 3115);
// BKE_sim_debug_data_add_dot(clmd->debug_data, x, col[0], col[1], col[2], "grid velocity", i, j, 3115);
BKE_sim_debug_data_add_circle(clmd->debug_data, x, 0.01f, col[0], col[1], col[2], "grid velocity", i, j, 3115);
}
#endif
}
}
}
}
#endif
BPH_hair_volume_free_vertex_grid(grid);
}
}
static void cloth_hair_update_bending_targets(ClothModifierData *clmd)
{
Cloth *cloth = clmd->clothObject;
LinkNode *search = NULL;
float hair_frame[3][3], dir_old[3], dir_new[3];
int prev_mn; /* to find hair chains */
if (!clmd->hairdata)
return;
/* XXX Note: we need to propagate frames from the root up,
* but structural hair springs are stored in reverse order.
* The bending springs however are then inserted in the same
* order as vertices again ...
* This messy situation can be resolved when solver data is
* generated directly from a dedicated hair system.
*/
prev_mn = -1;
for (search = cloth->springs; search; search = search->next) {
ClothSpring *spring = search->link;
ClothHairData *hair_ij, *hair_kl;
bool is_root = spring->kl != prev_mn;
if (spring->type != CLOTH_SPRING_TYPE_BENDING_ANG) {
continue;
}
hair_ij = &clmd->hairdata[spring->ij];
hair_kl = &clmd->hairdata[spring->kl];
if (is_root) {
/* initial hair frame from root orientation */
copy_m3_m3(hair_frame, hair_ij->rot);
/* surface normal is the initial direction,
* parallel transport then keeps it aligned to the hair direction
*/
copy_v3_v3(dir_new, hair_frame[2]);
}
copy_v3_v3(dir_old, dir_new);
sub_v3_v3v3(dir_new, cloth->verts[spring->mn].x, cloth->verts[spring->kl].x);
normalize_v3(dir_new);
#if 0
if (clmd->debug_data && (spring->ij == 0 || spring->ij == 1)) {
float a[3], b[3];
copy_v3_v3(a, cloth->verts[spring->kl].x);
// BKE_sim_debug_data_add_dot(clmd->debug_data, cloth_vert ? cloth_vert->x : key->co, 1, 1, 0, "frames", 8246, p, k);
mul_v3_v3fl(b, hair_frame[0], clmd->sim_parms->avg_spring_len);
BKE_sim_debug_data_add_vector(clmd->debug_data, a, b, 1, 0, 0, "frames", 8247, spring->kl, spring->mn);
mul_v3_v3fl(b, hair_frame[1], clmd->sim_parms->avg_spring_len);
BKE_sim_debug_data_add_vector(clmd->debug_data, a, b, 0, 1, 0, "frames", 8248, spring->kl, spring->mn);
mul_v3_v3fl(b, hair_frame[2], clmd->sim_parms->avg_spring_len);
BKE_sim_debug_data_add_vector(clmd->debug_data, a, b, 0, 0, 1, "frames", 8249, spring->kl, spring->mn);
}
#endif
/* get local targets for kl/mn vertices by putting rest targets into the current frame,
* then multiply with the rest length to get the actual goals
*/
mul_v3_m3v3(spring->target, hair_frame, hair_kl->rest_target);
mul_v3_fl(spring->target, spring->restlen);
/* move frame to next hair segment */
cloth_parallel_transport_hair_frame(hair_frame, dir_old, dir_new);
prev_mn = spring->mn;
}
}
