[Bf-blender-cvs] [9faf240] hair_immediate_fixes: Use the S matrix of the modifier CG algorithm for implementing collision responses.
Lukas Tönne
noreply at git.blender.org
Thu Sep 4 14:23:30 CEST 2014
Commit: 9faf2408fbab424ebae87f4e845f377dd5c9032c
Author: Lukas Tönne
Date: Thu Sep 4 14:22:22 2014 +0200
Branches: hair_immediate_fixes
https://developer.blender.org/rB9faf2408fbab424ebae87f4e845f377dd5c9032c
Use the S matrix of the modifier CG algorithm for implementing collision
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.
===================================================================
M source/blender/blenkernel/BKE_cloth.h
M source/blender/blenkernel/intern/collision.c
M source/blender/blenkernel/intern/implicit.c
===================================================================
diff --git a/source/blender/blenkernel/BKE_cloth.h b/source/blender/blenkernel/BKE_cloth.h
index 151a2b5..df11827 100644
--- a/source/blender/blenkernel/BKE_cloth.h
+++ b/source/blender/blenkernel/BKE_cloth.h
@@ -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]);
+
////////////////////////////////////////////////
diff --git a/source/blender/blenkernel/intern/collision.c b/source/blender/blenkernel/intern/collision.c
index 96645c2..f1b0908 100644
--- a/source/blender/blenkernel/intern/collision.c
+++ b/source/blender/blenkernel/intern/collision.c
@@ -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)
{
diff --git a/source/blender/blenkernel/intern/implicit.c b/source/blender/blenkernel/intern/implicit.c
index b3b2166..47c5bc07 100644
--- a/source/blender/blenkernel/intern/implicit.c
+++ b/source/blender/blenkernel/intern/implicit.c
@@ -357,8 +357,10 @@ 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
@@ -1950,23 +1952,30 @@ 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);
}
}
@@ -1976,21 +1985,34 @@ 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));
}
}
}
@@ -2290,6 +2312,12 @@ 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) {
@@ -2298,7 +2326,7 @@ 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);
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