forked from bartvdbraak/blender
Implemented internal hair pressure to prevent hair from collapsing in
on itself. This uses the same voxel structure as the hair smoothing algorithm. A slightly different method was suggested in the original paper (Volumetric Methods for Simulation and Rendering of Hair), but this is based on directing hair based on a target density, which is another way of implementing global goals. Our own approach is to define a pressure threshold above which the hair is repelled in the density gradient direction to simulate internal pressure from collisions.
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@ -316,6 +316,8 @@ class PARTICLE_PT_hair_dynamics(ParticleButtonsPanel, Panel):
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sub.prop(cloth, "bending_stiffness", text="Bending")
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sub.prop(cloth, "internal_friction", slider=True)
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sub.prop(cloth, "collider_friction", slider=True)
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sub.prop(cloth, "pressure", slider=True)
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sub.prop(cloth, "pressure_threshold", slider=True)
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col = split.column()
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col.label(text="Damping:")
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@ -1275,7 +1275,8 @@ BLI_INLINE int hair_grid_interp_weights(int res, const float gmin[3], const floa
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return offset;
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}
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BLI_INLINE void hair_grid_interpolate(const HairGridVert *grid, int res, const float gmin[3], const float scale[3], const float vec[3], float *density, float velocity[3])
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BLI_INLINE void hair_grid_interpolate(const HairGridVert *grid, int res, const float gmin[3], const float scale[3], const float vec[3],
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float *density, float velocity[3], float density_gradient[3])
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{
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HairGridVert data[8];
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float uvw[3], muvw[3];
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@ -1311,6 +1312,22 @@ BLI_INLINE void hair_grid_interpolate(const HairGridVert *grid, int res, const f
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uvw[1]*( muvw[0]*data[6].velocity[k] + uvw[0]*data[7].velocity[k] ) );
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}
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}
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if (density_gradient) {
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density_gradient[0] = muvw[1] * muvw[2] * ( data[0].density - data[1].density ) +
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uvw[1] * muvw[2] * ( data[2].density - data[3].density ) +
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muvw[1] * uvw[2] * ( data[4].density - data[5].density ) +
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uvw[1] * uvw[2] * ( data[6].density - data[7].density );
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density_gradient[1] = muvw[2] * muvw[0] * ( data[0].density - data[2].density ) +
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uvw[2] * muvw[0] * ( data[4].density - data[6].density ) +
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muvw[2] * uvw[0] * ( data[1].density - data[3].density ) +
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uvw[2] * uvw[0] * ( data[5].density - data[7].density );
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density_gradient[2] = muvw[2] * muvw[0] * ( data[0].density - data[4].density ) +
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uvw[2] * muvw[0] * ( data[1].density - data[5].density ) +
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muvw[2] * uvw[0] * ( data[2].density - data[6].density ) +
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uvw[2] * uvw[0] * ( data[3].density - data[7].density );
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}
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}
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static void hair_velocity_smoothing(const HairGridVert *hairgrid, const float gmin[3], const float scale[3], float smoothfac,
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@ -1321,9 +1338,7 @@ static void hair_velocity_smoothing(const HairGridVert *hairgrid, const float gm
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for (v = 0; v < numverts; v++) {
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float density, velocity[3];
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hair_grid_interpolate(hairgrid, hair_grid_res, gmin, scale, lX[v], &density, velocity);
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if (len_v3(velocity) > 10.0f)
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printf("a bit too much\n");
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hair_grid_interpolate(hairgrid, hair_grid_res, gmin, scale, lX[v], &density, velocity, NULL);
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sub_v3_v3(velocity, lV[v]);
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madd_v3_v3fl(lF[v], velocity, smoothfac);
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@ -1346,6 +1361,26 @@ static void hair_velocity_collision(const HairGridVert *collgrid, const float gm
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}
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}
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static void hair_pressure_force(const HairGridVert *hairgrid, const float gmin[3], const float scale[3], float pressurefac, float minpressure,
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lfVector *lF, lfVector *lX, unsigned int numverts)
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{
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int v;
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/* calculate forces */
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for (v = 0; v < numverts; v++) {
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float density, gradient[3], gradlen;
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hair_grid_interpolate(hairgrid, hair_grid_res, gmin, scale, lX[v], &density, NULL, gradient);
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gradlen = normalize_v3(gradient) - minpressure;
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if (gradlen < 0.0f)
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continue;
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mul_v3_fl(gradient, gradlen);
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madd_v3_v3fl(lF[v], gradient, pressurefac);
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}
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}
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static void hair_volume_get_boundbox(lfVector *lX, unsigned int numverts, float gmin[3], float gmax[3])
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{
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int i;
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@ -1531,6 +1566,11 @@ static void hair_volume_forces(ClothModifierData *clmd, lfVector *lF, lfVector *
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/* 2.0f is an experimental value that seems to give good results */
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float smoothfac = 2.0f * clmd->sim_parms->velocity_smooth;
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float collfac = 2.0f * clmd->sim_parms->collider_friction;
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float pressfac = clmd->sim_parms->pressure;
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float minpress = clmd->sim_parms->pressure_threshold;
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if (smoothfac <= 0.0f && collfac <= 0.0f && pressfac <= 0.0f)
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return;
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hair_volume_get_boundbox(lX, numverts, gmin, gmax);
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hair_grid_get_scale(hair_grid_res, gmin, gmax, scale);
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@ -1540,6 +1580,7 @@ static void hair_volume_forces(ClothModifierData *clmd, lfVector *lF, lfVector *
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hair_velocity_smoothing(hairgrid, gmin, scale, smoothfac, lF, lX, lV, numverts);
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hair_velocity_collision(collgrid, gmin, scale, collfac, lF, lX, lV, numverts);
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hair_pressure_force(hairgrid, gmin, scale, pressfac, minpress, lF, lX, numverts);
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MEM_freeN(hairgrid);
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MEM_freeN(collgrid);
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@ -1645,7 +1686,6 @@ static void cloth_calc_force(ClothModifierData *clmd, float UNUSED(frame), lfVec
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init_lfvector(lF, gravity, numverts);
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if (clmd->sim_parms->velocity_smooth > 0.0f || clmd->sim_parms->collider_friction > 0.0f)
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hair_volume_forces(clmd, lF, lX, lV, numverts);
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/* multiply lF with mass matrix
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@ -69,6 +69,8 @@ typedef struct ClothSimSettings {
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float goalspring;
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float goalfrict;
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float velocity_smooth; /* smoothing of velocities for hair */
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float pressure; /* pressure factor from hair density */
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float pressure_threshold; /* minimum density for hair pressure */
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float collider_friction; /* friction with colliders */
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float vel_damping; /* damp the velocity to speed up getting to the resting position */
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float shrink_min; /* min amount to shrink cloth by 0.0f (no shrink) - 1.0f (shrink to nothing) */
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@ -325,6 +325,18 @@ static void rna_def_cloth_sim_settings(BlenderRNA *brna)
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RNA_def_property_ui_text(prop, "Collider Friction", "");
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RNA_def_property_update(prop, 0, "rna_cloth_update");
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prop = RNA_def_property(srna, "pressure", PROP_FLOAT, PROP_NONE);
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RNA_def_property_float_sdna(prop, NULL, "pressure");
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RNA_def_property_range(prop, 0.0f, 1000.0f);
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RNA_def_property_ui_text(prop, "Internal Pressure", "Generate outward force based on hair density");
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RNA_def_property_update(prop, 0, "rna_cloth_update");
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prop = RNA_def_property(srna, "pressure_threshold", PROP_FLOAT, PROP_NONE);
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RNA_def_property_float_sdna(prop, NULL, "pressure_threshold");
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RNA_def_property_range(prop, 0.0f, 1000.0f);
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RNA_def_property_ui_text(prop, "Internal Pressure Threshold", "No pressure force is generated below this pressure value");
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RNA_def_property_update(prop, 0, "rna_cloth_update");
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/* mass */
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prop = RNA_def_property(srna, "mass", PROP_FLOAT, PROP_NONE);
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