sandey/blender
1
0
Fork 0
forked from bartvdbraak/blender
Code Pull Requests Activity

Use the S matrix of the modifier CG algorithm for implementing collision

Browse Source 
responses.

The S matrix together with the z Vector encodes the degrees of freedom
of a colliding hair point and the target velocity change. In a collision
the hair vertex is restricted in the normal direction (when moving
toward the collider) and the collision dynamics define target velocity.
This commit is contained in:
Lukas Tönne 2014-09-04 14:22:22 +02:00
parent 02ab74eb55
commit 27ecda9995
3 changed files with 126 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
source/blender/blenkernel/BKE_cloth.h
View File

@ -44,6 +44,7 @@ struct ClothModifierData;
struct CollisionModifierData;
struct CollisionTree;
struct VoxelData;
struct PartDeflect;
#define DO_INLINE MALWAYS_INLINE
@ -201,6 +202,9 @@ void cloth_find_point_contacts(struct Object *ob, struct ClothModifierData *clmd
ColliderContacts **r_collider_contacts, int *r_totcolliders);
void cloth_free_contacts(ColliderContacts *collider_contacts, int totcolliders);
bool cloth_points_collpair_response(struct ClothModifierData *clmd, struct CollisionModifierData *collmd, struct PartDeflect *pd,
struct CollPair *collpair, float dt, float r_impulse[3]);
////////////////////////////////////////////////

76
source/blender/blenkernel/intern/collision.c
View File

@ -958,6 +958,82 @@ BLI_INLINE void max_v3_v3v3(float r[3], const float a[3], const float b[3])
r[2] = max_ff(a[2], b[2]);
}
bool cloth_points_collpair_response(ClothModifierData *clmd, CollisionModifierData *collmd, PartDeflect *pd, CollPair *collpair, float dt, float r_impulse[3])
{
bool result = false;
float restitution = (1.0f - clmd->coll_parms->damping) * (1.0f - pd->pdef_sbdamp);
Cloth *cloth1 = clmd->clothObject;
float u1, u2, u3;
float v1[3], v2_old[3], v2_new[3], v_rel_old[3], v_rel_new[3];
float epsilon2 = BLI_bvhtree_getepsilon ( collmd->bvhtree );
float margin_distance = collpair->distance - epsilon2;
float mag_v_rel;
zero_v3(r_impulse);
if (margin_distance > 0.0f)
return false; /* XXX tested before already? */
/* only handle static collisions here */
if ( collpair->flag & COLLISION_IN_FUTURE )
return false;
/* compute barycentric coordinates */
collision_compute_barycentric(collpair->pb,
collmd->current_x[collpair->bp1].co,
collmd->current_x[collpair->bp2].co,
collmd->current_x[collpair->bp3].co,
&u1, &u2, &u3 );
/* Calculate relative velocity */
copy_v3_v3(v1, cloth1->verts[collpair->ap1].tv);
collision_interpolateOnTriangle(v2_new, collmd->current_v[collpair->bp1].co, collmd->current_v[collpair->bp2].co, collmd->current_v[collpair->bp3].co, u1, u2, u3);
/* XXX assume constant velocity of the collider for now */
copy_v3_v3(v2_old, v2_new);
/* relative velocity = velocity of the cloth point relative to the collider */
sub_v3_v3v3(v_rel_old, v1, v2_old);
sub_v3_v3v3(v_rel_new, v1, v2_new);
/* normal component of the relative velocity */
mag_v_rel = dot_v3v3(v_rel_old, collpair->normal);
/* only valid when moving toward the collider */
if (mag_v_rel < -ALMOST_ZERO) {
float v_nor_old, v_nor_new;
float v_tan_old[3], v_tan_new[3];
float bounce, repulse;
/* Collision response based on
* "Simulating Complex Hair with Robust Collision Handling" (Choe, Choi, Ko, ACM SIGGRAPH 2005)
* http://graphics.snu.ac.kr/publications/2005-choe-HairSim/Choe_2005_SCA.pdf
*/
v_nor_old = mag_v_rel;
v_nor_new = dot_v3v3(v_rel_new, collpair->normal);
madd_v3_v3v3fl(v_tan_old, v_rel_old, collpair->normal, -v_nor_old);
madd_v3_v3v3fl(v_tan_new, v_rel_new, collpair->normal, -v_nor_new);
repulse = -margin_distance / dt + dot_v3v3(v1, collpair->normal);
if (margin_distance < -epsilon2) {
bounce = -v_nor_new + v_nor_old * restitution;
mul_v3_v3fl(r_impulse, collpair->normal, max_ff(repulse, bounce));
}
else {
bounce = 0.0f;
mul_v3_v3fl(r_impulse, collpair->normal, repulse);
}
result = true;
}
return result;
}
static bool cloth_points_collision_response_static(ClothModifierData *clmd, CollisionModifierData *collmd, PartDeflect *pd,
CollPair *collpair, CollPair *collision_end, float dt)
{

64
source/blender/blenkernel/intern/implicit.c
View File

@ -349,8 +349,10 @@ static void print_sparse_matrix(fmatrix3x3 *m)
{
if (m) {
unsigned int i;
for (i = 0; i < m[0].vcount + m[0].scount; i++)
for (i = 0; i < m[0].vcount + m[0].scount; i++) {
printf("%d:\n", i);
print_fmatrix(m[i].m);
}
}
}
#endif
@ -1756,23 +1758,30 @@ bool implicit_hair_volume_get_texture_data(Object *UNUSED(ob), ClothModifierData
/* ================================ */
/* Init constraint matrix */
static void setup_constraint_matrix(ClothVertex *verts, int numverts, ColliderContacts *contacts, int totcolliders, fmatrix3x3 *S, SimDebugData *debug_data)
/* Init constraint matrix
* This is part of the modified CG method suggested by Baraff/Witkin in
* "Large Steps in Cloth Simulation" (Siggraph 1998)
*/
static void setup_constraint_matrix(ClothModifierData *clmd, ColliderContacts *contacts, int totcolliders, lfVector *V, fmatrix3x3 *S, lfVector *z, float dt)
{
int i, j;
ClothVertex *verts = clmd->clothObject->verts;
int numverts = clmd->clothObject->numverts;
int i, j, v;
/* Clear matrix from old vertex constraints */
for (i = 0; i < S[0].vcount; i++)
S[i].c = S[i].r = 0;
for (v = 0; v < S[0].vcount; v++)
S[v].c = S[v].r = 0;
/* pinned vertex constraints */
for (i = 0; i < numverts; i++) {
S[i].c = S[i].r = i;
if (verts[i].flags & CLOTH_VERT_FLAG_PINNED) {
zero_m3(S[i].m);
for (v = 0; v < numverts; v++) {
S[v].c = S[v].r = v;
if (verts[v].flags & CLOTH_VERT_FLAG_PINNED) {
negate_v3_v3(z[v], verts[v].v);
zero_m3(S[v].m);
}
else {
unit_m3(S[i].m);
zero_v3(z[v]);
unit_m3(S[v].m);
}
}
@ -1782,21 +1791,34 @@ static void setup_constraint_matrix(ClothVertex *verts, int numverts, ColliderCo
CollPair *collpair = &ct->collisions[j];
int v = collpair->face1;
float cmat[3][3];
float impulse[3];
/* pinned verts handled separately */
if (verts[v].flags & CLOTH_VERT_FLAG_PINNED)
continue;
/* calculate collision response */
// if (!cloth_points_collpair_response(clmd, ct->collmd, ct->ob->pd, collpair, dt, impulse))
// continue;
cloth_points_collpair_response(clmd, ct->collmd, ct->ob->pd, collpair, dt, impulse);
// add_v3_v3(z[v], impulse);
negate_v3_v3(z[v], V[v]);
// sub_v3_v3(z[v], verts[v].v);
/* modify S to enforce velocity constraint in normal direction */
mul_fvectorT_fvector(cmat, collpair->normal, collpair->normal);
sub_m3_m3m3(S[v].m, I, cmat);
BKE_sim_debug_data_add_dot(debug_data, collpair->pa, 0, 1, 0, "collision", hash_collpair(936, collpair));
BKE_sim_debug_data_add_dot(debug_data, collpair->pb, 1, 0, 0, "collision", hash_collpair(937, collpair));
BKE_sim_debug_data_add_line(debug_data, collpair->pa, collpair->pb, 0.7, 0.7, 0.7, "collision", hash_collpair(938, collpair));
BKE_sim_debug_data_add_dot(clmd->debug_data, collpair->pa, 0, 1, 0, "collision", hash_collpair(936, collpair));
BKE_sim_debug_data_add_dot(clmd->debug_data, collpair->pb, 1, 0, 0, "collision", hash_collpair(937, collpair));
BKE_sim_debug_data_add_line(clmd->debug_data, collpair->pa, collpair->pb, 0.7, 0.7, 0.7, "collision", hash_collpair(938, collpair));
{
float nor[3];
mul_v3_v3fl(nor, collpair->normal, collpair->distance);
BKE_sim_debug_data_add_vector(debug_data, collpair->pb, nor, 1, 1, 0, "collision", hash_collpair(939, collpair));
// float nor[3];
// mul_v3_v3fl(nor, collpair->normal, collpair->distance);
// BKE_sim_debug_data_add_vector(clmd->debug_data, collpair->pb, nor, 1, 1, 0, "collision", hash_collpair(939, collpair));
BKE_sim_debug_data_add_vector(clmd->debug_data, collpair->pb, impulse, 1, 1, 0, "collision", hash_collpair(940, collpair));
// BKE_sim_debug_data_add_vector(clmd->debug_data, collpair->pb, collpair->normal, 1, 1, 0, "collision", hash_collpair(941, collpair));
}
}
}
@ -2096,6 +2118,12 @@ int implicit_solver(Object *ob, float frame, ClothModifierData *clmd, ListBase *
while (step < tf) {
/* copy velocities for collision */
for (i = 0; i < numverts; i++) {
copy_v3_v3(verts[i].tv, id->V[i]);
copy_v3_v3(verts[i].v, verts[i].tv);
}
/* determine contact points */
if (clmd->coll_parms->flags & CLOTH_COLLSETTINGS_FLAG_ENABLED) {
if (clmd->coll_parms->flags & CLOTH_COLLSETTINGS_FLAG_POINTS) {
@ -2104,7 +2132,7 @@ int implicit_solver(Object *ob, float frame, ClothModifierData *clmd, ListBase *
}
/* setup vertex constraints for pinned vertices and contacts */
setup_constraint_matrix(verts, cloth->numverts, contacts, totcolliders, id->S, clmd->debug_data);
setup_constraint_matrix(clmd, contacts, totcolliders, id->V, id->S, id->z, dt);
// damping velocity for artistic reasons
mul_lfvectorS(id->V, id->V, clmd->sim_parms->vel_damping, numverts);