Commit: d43170d09dd27ae522d3943afa00c55838118ab4
Author: Lukas Tönne
Date: Wed Sep 17 10:11:03 2014 +0200
Branches: master
https://developer.blender.org/rBd43170d09dd27ae522d3943afa00c55838118ab4
Add weak repulsion forces to hair collision response to keep the hair
at a the margin distance ("outer" softbody margin).
This has to be clamped arbitrarily unfortunately, otherwise the
repulsion force can add too much energy into the system. A factor of
4 * restitution impulse seems to give good results for now, this can
be refined later on if necessary.
===================================================================
M source/blender/physics/intern/BPH_mass_spring.cpp
===================================================================
diff --git a/source/blender/physics/intern/BPH_mass_spring.cpp
b/source/blender/physics/intern/BPH_mass_spring.cpp
index 568aea6..e910739 100644
--- a/source/blender/physics/intern/BPH_mass_spring.cpp
+++ b/source/blender/physics/intern/BPH_mass_spring.cpp
@@ -107,7 +107,7 @@ void BKE_cloth_solver_set_positions(ClothModifierData *clmd)
}
}
-static bool collision_response(ClothModifierData *clmd, CollisionModifierData
*collmd, CollPair *collpair, float restitution, float r_impulse[3])
+static bool collision_response(ClothModifierData *clmd, CollisionModifierData
*collmd, CollPair *collpair, float dt, float restitution, float r_impulse[3])
{
Cloth *cloth = clmd->clothObject;
int index = collpair->ap1;
@@ -154,19 +154,20 @@ static bool collision_response(ClothModifierData *clmd,
CollisionModifierData *c
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);
- /* TODO repulsion forces can easily destabilize the system,
- * have to clamp them or construct a linear spring instead
+ bounce = -v_nor_old * restitution;
+
+ repulse = -margin_distance / dt; /* base repulsion velocity in
normal direction */
+ /* XXX this clamping factor is quite arbitrary ...
+ * not sure if there is a more scientific approach, but seems
to give good results
*/
-// repulse = -margin_distance / dt + dot_v3v3(v1,
collpair->normal);
- repulse = 0.0f;
+ CLAMP(repulse, 0.0f, 4.0f * bounce);
if (margin_distance < -epsilon2) {
- bounce = -(v_nor_new + v_nor_old * restitution);
- mul_v3_v3fl(r_impulse, collpair->normal,
max_ff(repulse, bounce));
+ mul_v3_v3fl(r_impulse, collpair->normal,
max_ff(repulse, bounce) - v_nor_new);
}
else {
bounce = 0.0f;
- mul_v3_v3fl(r_impulse, collpair->normal, repulse);
+ mul_v3_v3fl(r_impulse, collpair->normal, repulse -
v_nor_new);
}
result = true;
@@ -220,21 +221,21 @@ static void cloth_setup_constraints(ClothModifierData
*clmd, ColliderContacts *c
continue;
/* calculate collision response */
- if (!collision_response(clmd, ct->collmd, collpair,
restitution, impulse))
+ if (!collision_response(clmd, ct->collmd, collpair, dt,
restitution, impulse))
continue;
BPH_mass_spring_add_constraint_ndof2(data, v,
collpair->normal, impulse);
++verts[v].impulse_count;
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));
+// 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));
{ /* DEBUG */
-// 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));
+ float nor[3];
+ mul_v3_v3fl(nor, collpair->normal,
-collpair->distance);
+ BKE_sim_debug_data_add_vector(clmd->debug_data,
collpair->pa, 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));
}
}
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