diff options
Diffstat (limited to 'source/blender/physics/intern/implicit_blender.c')
| -rw-r--r-- | source/blender/physics/intern/implicit_blender.c | 38 |
1 files changed, 27 insertions, 11 deletions
diff --git a/source/blender/physics/intern/implicit_blender.c b/source/blender/physics/intern/implicit_blender.c index ddd71eb93e3..677e566ff39 100644 --- a/source/blender/physics/intern/implicit_blender.c +++ b/source/blender/physics/intern/implicit_blender.c @@ -1585,9 +1585,13 @@ BLI_INLINE void apply_spring(Implicit_Data *data, int i, int j, const float f[3] } bool BPH_mass_spring_force_spring_linear(Implicit_Data *data, int i, int j, float restlen, - float stiffness, float damping, bool no_compress, float clamp_force) + float stiffness_tension, float damping_tension, + float stiffness_compression, float damping_compression, + bool resist_compress, bool new_compress, float clamp_force) { float extent[3], length, dir[3], vel[3]; + float f[3], dfdx[3][3], dfdv[3][3]; + float damping = 0; // calculate elonglation spring_length(data, i, j, extent, dir, &length, vel); @@ -1595,29 +1599,41 @@ bool BPH_mass_spring_force_spring_linear(Implicit_Data *data, int i, int j, floa /* This code computes not only the force, but also its derivative. Zero derivative effectively disables the spring for the implicit solver. Thus length > restlen makes cloth unconstrained at the start of simulation. */ - if ((length >= restlen && length > 0) || no_compress) { - float stretch_force, f[3], dfdx[3][3], dfdv[3][3]; + if ((length >= restlen && length > 0) || resist_compress) { + float stretch_force; + + damping = damping_tension; - stretch_force = stiffness * (length - restlen); + stretch_force = stiffness_tension * (length - restlen); if (clamp_force > 0.0f && stretch_force > clamp_force) { stretch_force = clamp_force; } mul_v3_v3fl(f, dir, stretch_force); - // Ascher & Boxman, p.21: Damping only during elonglation - // something wrong with it... - madd_v3_v3fl(f, dir, damping * dot_v3v3(vel, dir)); + dfdx_spring(dfdx, dir, length, restlen, stiffness_tension); + } + else if (new_compress) { + /* This is based on the Choi and Ko bending model, which works surprisingly well for compression. */ + float kb = stiffness_compression; + float cb = kb; /* cb equal to kb seems to work, but a factor can be added if necessary */ - dfdx_spring(dfdx, dir, length, restlen, stiffness); - dfdv_damp(dfdv, dir, damping); + damping = damping_compression; - apply_spring(data, i, j, f, dfdx, dfdv); + mul_v3_v3fl(f, dir, fbstar(length, restlen, kb, cb)); - return true; + outerproduct(dfdx, dir, dir); + mul_m3_fl(dfdx, fbstar_jacobi(length, restlen, kb, cb)); } else { return false; } + + madd_v3_v3fl(f, dir, damping * dot_v3v3(vel, dir)); + dfdv_damp(dfdv, dir, damping); + + apply_spring(data, i, j, f, dfdx, dfdv); + + return true; } /* See "Stable but Responsive Cloth" (Choi, Ko 2005) */ |