Commit: 42a02c61e863a187da9b35887fbb0e2cb40aa19c
Author: Lukas Tönne
Date: Thu Aug 28 14:55:55 2014 +0200
Branches: hair_immediate_fixes
https://developer.blender.org/rB42a02c61e863a187da9b35887fbb0e2cb40aa19c
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.
===================================================================
M release/scripts/startup/bl_ui/properties_particle.py
M source/blender/blenkernel/intern/implicit.c
M source/blender/makesdna/DNA_cloth_types.h
M source/blender/makesrna/intern/rna_cloth.c
===================================================================
diff --git a/release/scripts/startup/bl_ui/properties_particle.py
b/release/scripts/startup/bl_ui/properties_particle.py
index 30fc3a9..7124271 100644
--- a/release/scripts/startup/bl_ui/properties_particle.py
+++ b/release/scripts/startup/bl_ui/properties_particle.py
@@ -292,6 +292,8 @@ class PARTICLE_PT_hair_dynamics(ParticleButtonsPanel,
Panel):
sub.prop(cloth, "bending_stiffness", text="Bending")
sub.prop(cloth, "internal_friction", slider=True)
sub.prop(cloth, "collider_friction", slider=True)
+ sub.prop(cloth, "pressure", slider=True)
+ sub.prop(cloth, "pressure_threshold", slider=True)
col = split.column()
col.label(text="Damping:")
diff --git a/source/blender/blenkernel/intern/implicit.c
b/source/blender/blenkernel/intern/implicit.c
index 488ca18..db77190 100644
--- a/source/blender/blenkernel/intern/implicit.c
+++ b/source/blender/blenkernel/intern/implicit.c
@@ -1469,7 +1469,8 @@ BLI_INLINE int hair_grid_interp_weights(int res, const
float gmin[3], const floa
return offset;
}
-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])
+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], float
density_gradient[3])
{
HairGridVert data[8];
float uvw[3], muvw[3];
@@ -1505,6 +1506,22 @@ BLI_INLINE void hair_grid_interpolate(const HairGridVert
*grid, int res, const f
uvw[1]*(
muvw[0]*data[6].velocity[k] + uvw[0]*data[7].velocity[k] ) );
}
}
+ if (density_gradient) {
+ density_gradient[0] = muvw[1] * muvw[2] * ( data[0].density -
data[1].density ) +
+ uvw[1] * muvw[2] * ( data[2].density -
data[3].density ) +
+ muvw[1] * uvw[2] * ( data[4].density -
data[5].density ) +
+ uvw[1] * uvw[2] * ( data[6].density -
data[7].density );
+
+ density_gradient[1] = muvw[2] * muvw[0] * ( data[0].density -
data[2].density ) +
+ uvw[2] * muvw[0] * ( data[4].density -
data[6].density ) +
+ muvw[2] * uvw[0] * ( data[1].density -
data[3].density ) +
+ uvw[2] * uvw[0] * ( data[5].density -
data[7].density );
+
+ density_gradient[2] = muvw[2] * muvw[0] * ( data[0].density -
data[4].density ) +
+ uvw[2] * muvw[0] * ( data[1].density -
data[5].density ) +
+ muvw[2] * uvw[0] * ( data[2].density -
data[6].density ) +
+ uvw[2] * uvw[0] * ( data[3].density -
data[7].density );
+ }
}
static void hair_velocity_smoothing(const HairGridVert *hairgrid, const float
gmin[3], const float scale[3], float smoothfac,
@@ -1515,9 +1532,7 @@ static void hair_velocity_smoothing(const HairGridVert
*hairgrid, const float gm
for (v = 0; v < numverts; v++) {
float density, velocity[3];
- hair_grid_interpolate(hairgrid, hair_grid_res, gmin, scale,
lX[v], &density, velocity);
- if (len_v3(velocity) > 10.0f)
- printf("a bit too much\n");
+ hair_grid_interpolate(hairgrid, hair_grid_res, gmin, scale,
lX[v], &density, velocity, NULL);
sub_v3_v3(velocity, lV[v]);
madd_v3_v3fl(lF[v], velocity, smoothfac);
@@ -1540,6 +1555,26 @@ static void hair_velocity_collision(const HairGridVert
*collgrid, const float gm
}
}
+static void hair_pressure_force(const HairGridVert *hairgrid, const float
gmin[3], const float scale[3], float pressurefac, float minpressure,
+ lfVector *lF, lfVector *lX, unsigned int
numverts)
+{
+ int v;
+
+ /* calculate forces */
+ for (v = 0; v < numverts; v++) {
+ float density, gradient[3], gradlen;
+
+ hair_grid_interpolate(hairgrid, hair_grid_res, gmin, scale,
lX[v], &density, NULL, gradient);
+
+ gradlen = normalize_v3(gradient) - minpressure;
+ if (gradlen < 0.0f)
+ continue;
+ mul_v3_fl(gradient, gradlen);
+
+ madd_v3_v3fl(lF[v], gradient, pressurefac);
+ }
+}
+
static void hair_volume_get_boundbox(lfVector *lX, unsigned int numverts,
float gmin[3], float gmax[3])
{
int i;
@@ -1725,6 +1760,11 @@ static void hair_volume_forces(ClothModifierData *clmd,
lfVector *lF, lfVector *
/* 2.0f is an experimental value that seems to give good results */
float smoothfac = 2.0f * clmd->sim_parms->velocity_smooth;
float collfac = 2.0f * clmd->sim_parms->collider_friction;
+ float pressfac = clmd->sim_parms->pressure;
+ float minpress = clmd->sim_parms->pressure_threshold;
+
+ if (smoothfac <= 0.0f && collfac <= 0.0f && pressfac <= 0.0f)
+ return;
hair_volume_get_boundbox(lX, numverts, gmin, gmax);
hair_grid_get_scale(hair_grid_res, gmin, gmax, scale);
@@ -1734,6 +1774,7 @@ static void hair_volume_forces(ClothModifierData *clmd,
lfVector *lF, lfVector *
hair_velocity_smoothing(hairgrid, gmin, scale, smoothfac, lF, lX, lV,
numverts);
hair_velocity_collision(collgrid, gmin, scale, collfac, lF, lX, lV,
numverts);
+ hair_pressure_force(hairgrid, gmin, scale, pressfac, minpress, lF, lX,
numverts);
MEM_freeN(hairgrid);
MEM_freeN(collgrid);
@@ -1839,8 +1880,7 @@ static void cloth_calc_force(ClothModifierData *clmd,
float UNUSED(frame), lfVec
init_lfvector(lF, gravity, numverts);
- if (clmd->sim_parms->velocity_smooth > 0.0f ||
clmd->sim_parms->collider_friction > 0.0f)
- hair_volume_forces(clmd, lF, lX, lV, numverts);
+ hair_volume_forces(clmd, lF, lX, lV, numverts);
/* multiply lF with mass matrix
* force = mass * acceleration (in this case: gravity)
diff --git a/source/blender/makesdna/DNA_cloth_types.h
b/source/blender/makesdna/DNA_cloth_types.h
index 6c7d500..a9e066e 100644
--- a/source/blender/makesdna/DNA_cloth_types.h
+++ b/source/blender/makesdna/DNA_cloth_types.h
@@ -69,6 +69,8 @@ typedef struct ClothSimSettings {
float goalspring;
float goalfrict;
float velocity_smooth; /* smoothing of velocities for hair */
+ float pressure; /* pressure factor from hair
density */
+ float pressure_threshold; /* minimum density for hair pressure */
float collider_friction; /* friction with colliders */
float vel_damping; /* damp the velocity to speed up getting to the
resting position */
float shrink_min; /* min amount to shrink cloth by 0.0f (no shrink)
- 1.0f (shrink to nothing) */
diff --git a/source/blender/makesrna/intern/rna_cloth.c
b/source/blender/makesrna/intern/rna_cloth.c
index cecc39c..9ab6791 100644
--- a/source/blender/makesrna/intern/rna_cloth.c
+++ b/source/blender/makesrna/intern/rna_cloth.c
@@ -325,6 +325,18 @@ static void rna_def_cloth_sim_settings(BlenderRNA *brna)
RNA_def_property_ui_text(prop, "Collider Friction", "");
RNA_def_property_update(prop, 0, "rna_cloth_update");
+ prop = RNA_def_property(srna, "pressure", PROP_FLOAT, PROP_NONE);
+ RNA_def_property_float_sdna(prop, NULL, "pressure");
+ RNA_def_property_range(prop, 0.0f, 1000.0f);
+ RNA_def_property_ui_text(prop, "Internal Pressure", "Generate outward
force based on hair density");
+ RNA_def_property_update(prop, 0, "rna_cloth_update");
+
+ prop = RNA_def_property(srna, "pressure_threshold", PROP_FLOAT,
PROP_NONE);
+ RNA_def_property_float_sdna(prop, NULL, "pressure_threshold");
+ RNA_def_property_range(prop, 0.0f, 1000.0f);
+ RNA_def_property_ui_text(prop, "Internal Pressure Threshold", "No
pressure force is generated below this pressure value");
+ RNA_def_property_update(prop, 0, "rna_cloth_update");
+
/* mass */
prop = RNA_def_property(srna, "mass", PROP_FLOAT, PROP_NONE);
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