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Calculate bending targets based on the direction of previous segments. 

This makes the bending a truely local effect. Eventually target
directions should be based in a local coordinate frame that gets
parallel transported along the curve. This will allow non-straight
rest shapes for hairs as well as supporting twist forces. However,
calculating locally transformed spring forces is more complicated.
This commit is contained in:
Lukas Tönne 2014-09-19 16:53:35 +02:00
parent e5ae13b809
commit 00bb836e17
4 changed files with 20 additions and 22 deletions
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4
source/blender/blenkernel/intern/cloth.c
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@ -1302,9 +1302,9 @@ static int cloth_build_springs ( ClothModifierData *clmd, DerivedMesh *dm )
return 0;
}
spring->ij = tspring->kl;
spring->ij = tspring2->ij;
spring->kl = tspring->ij;
spring->mn = tspring2->ij;
spring->mn = tspring->kl;
spring->restlen = len_v3v3(cloth->verts[spring->kl].xrest, cloth->verts[spring->ij].xrest);
spring->type = CLOTH_SPRING_TYPE_BENDING_ANG;
spring->stiffness = (cloth->verts[spring->kl].bend_stiff + cloth->verts[spring->ij].bend_stiff) / 2.0f;

2
source/blender/physics/intern/BPH_mass_spring.cpp
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@ -394,7 +394,7 @@ BLI_INLINE void cloth_calc_spring_force(ClothModifierData *clmd, ClothSpring *s,
scaling = parms->bending + s->stiffness * fabsf(parms->max_bend - parms->bending);
cb = kb = scaling / (20.0f * (parms->avg_spring_len + FLT_EPSILON));
BPH_mass_spring_force_spring_bending_angular(data, s->ij, s->kl, s->matrix_index, s->restlen, kb, cb, s->f, s->dfdx, s->dfdv);
BPH_mass_spring_force_spring_bending_angular(data, s->ij, s->kl, s->mn, s->matrix_index, s->restlen, kb, cb, s->f, s->dfdx, s->dfdv);
#endif
}
}

2
source/blender/physics/intern/implicit.h
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@ -144,7 +144,7 @@ bool BPH_mass_spring_force_spring_bending(struct Implicit_Data *data, int i, int
float kb, float cb,
float r_f[3], float r_dfdx[3][3], float r_dfdv[3][3]);
/* Angular bending force based on local target vectors */
bool BPH_mass_spring_force_spring_bending_angular(struct Implicit_Data *data, int i, int j, int spring_index, float restlen,
bool BPH_mass_spring_force_spring_bending_angular(struct Implicit_Data *data, int i, int j, int k, int spring_index, float restlen,
float stiffness, float damping,
float r_f[3], float r_dfdx[3][3], float r_dfdv[3][3]);
/* Global goal spring */

34
source/blender/physics/intern/implicit_blender.c
View File

@ -1619,28 +1619,32 @@ bool BPH_mass_spring_force_spring_bending(Implicit_Data *data, int i, int j, int
/* Angular spring that pulls the vertex toward the local target
* See "Artistic Simulation of Curly Hair" (Pixar technical memo #12-03a)
*/
bool BPH_mass_spring_force_spring_bending_angular(Implicit_Data *data, int i, int j, int spring_index, float restlen,
bool BPH_mass_spring_force_spring_bending_angular(Implicit_Data *data, int i, int j, int k, int spring_index, float restlen,
float stiffness, float damping,
float r_f[3], float r_dfdx[3][3], float r_dfdv[3][3])
{
float target[3], targetdir[3];
float extent[3], dir[3], length;
float extent[3], dir[3];
float dist[3], vel[3];
float f[3], dfdx[3][3], dfdv[3][3];
target[0] = 0.0f;
target[1] = 0.0f;
target[2] = restlen;
sub_v3_v3v3(targetdir, data->X[j], data->X[i]);
normalize_v3(targetdir);
mul_v3_v3fl(target, targetdir, restlen);
{
float x[3], d[3];
root_to_world_v3(data, j, x, data->X[j]);
root_to_world_v3(data, j, d, target);
BKE_sim_debug_data_add_vector(data->debug_data, x, d, 1, 0, 0, "spoint", hash_vertex(935, j));
}
// calculate elonglation
// spring_length(data, i, j, extent, dir, &length, vel);
sub_v3_v3v3(extent, data->X[j], data->X[i]);
sub_v3_v3v3(vel, data->V[j], data->V[i]);
length = normalize_v3_v3(dir, extent);
normalize_v3_v3(targetdir, target);
sub_v3_v3v3(extent, data->X[k], data->X[j]);
sub_v3_v3v3(vel, data->V[k], data->V[j]);
normalize_v3_v3(dir, extent);
sub_v3_v3v3(dist, target, extent);
mul_v3_v3fl(f, dist, stiffness);
mul_v3_v3fl(f, dist, -stiffness);
madd_v3_v3fl(vel, dir, -dot_v3v3(vel, dir));
madd_v3_v3fl(f, vel, damping);
@ -1648,13 +1652,7 @@ bool BPH_mass_spring_force_spring_bending_angular(Implicit_Data *data, int i, in
zero_m3(dfdx);
zero_m3(dfdv);
// outerproduct(dfdx, dir, dir);
// mul_m3_fl(dfdx, fbstar_jacobi(length, restlen, kb, cb));
/* XXX damping not supported */
// zero_m3(dfdv);
apply_spring(data, i, j, spring_index, f, dfdx, dfdv);
apply_spring(data, j, k, spring_index, f, dfdx, dfdv);
if (r_f) copy_v3_v3(r_f, f);
if (r_dfdx) copy_m3_m3(r_dfdx, dfdx);