Commit: 77129b399d21fdd0376efbb0daaf22dbc2abfd90
Author: Lukas Tönne
Date: Tue Jul 29 15:44:29 2014 +0200
Branches: hair_system
https://developer.blender.org/rB77129b399d21fdd0376efbb0daaf22dbc2abfd90
Bending forces and damping for hair.
This adds some stiffness to hairs along bends, such that the hair does
no longer behave like a chain of freely rotating segments.
Note that there is no bending force on the root segment yet, which means
the hair swivels around the root point without resistance.
===================================================================
M release/scripts/startup/bl_ui/properties_data_modifier.py
M source/blender/hair/intern/HAIR_solver.cpp
M source/blender/hair/intern/HAIR_solver.h
M source/blender/makesdna/DNA_hair_types.h
M source/blender/makesrna/intern/rna_hair.c
===================================================================
diff --git a/release/scripts/startup/bl_ui/properties_data_modifier.py
b/release/scripts/startup/bl_ui/properties_data_modifier.py
index 9d6ebae..2f1fca4 100644
--- a/release/scripts/startup/bl_ui/properties_data_modifier.py
+++ b/release/scripts/startup/bl_ui/properties_data_modifier.py
@@ -1235,8 +1235,10 @@ class DATA_PT_modifiers(ModifierButtonsPanel, Panel):
row = col.row()
col2 = row.column()
col2.prop(params, "stretch_stiffness")
+ col2.prop(params, "bend_stiffness")
col2 = row.column()
col2.prop(params, "stretch_damping")
+ col2.prop(params, "bend_damping")
col.separator()
diff --git a/source/blender/hair/intern/HAIR_solver.cpp
b/source/blender/hair/intern/HAIR_solver.cpp
index be2c38c..433fecd 100644
--- a/source/blender/hair/intern/HAIR_solver.cpp
+++ b/source/blender/hair/intern/HAIR_solver.cpp
@@ -64,9 +64,8 @@ SolverData::~SolverData()
static float3 calc_bend(const Frame &frame, const float3 &co0, const float3
&co1)
{
- float3 dir;
- normalize_v3_v3(dir, co1 - co0);
- return float3(dot_v3_v3(dir, frame.normal), dot_v3_v3(dir,
frame.tangent), dot_v3_v3(dir, frame.cotangent));
+ float3 edge = co1 - co0;
+ return float3(dot_v3_v3(edge, frame.normal), dot_v3_v3(edge,
frame.tangent), dot_v3_v3(edge, frame.cotangent));
}
void SolverData::precompute_rest_bend()
@@ -150,7 +149,7 @@ float3 Solver::calc_velocity(Curve *curve, Point *point,
float time, Point::Stat
return state.vel;
}
-float3 Solver::calc_stretch(Curve *curve, Point *point0, Point *point1, float
time) const
+float3 Solver::calc_stretch_force(Curve *curve, Point *point0, Point *point1,
float time) const
{
/* XXX this could be cached in SolverData */
float3 dir;
@@ -164,14 +163,34 @@ float3 Solver::calc_stretch(Curve *curve, Point *point0,
Point *point1, float ti
return stretch_force + stretch_damp;
}
-float3 Solver::calc_acceleration(Curve *curve, Point *point, float time,
float3 prev_stretch, float3 stretch, Point::State &state) const
+#if 0
+float3 Solver::calc_bend_force(Curve *curve, const Frame &frame, Point
*point0, Point *point1, float time) const
+{
+ float3 bend = calc_bend(frame, point0->cur.co, point1->cur.co);
+
+
+}
+#endif
+
+float3 Solver::calc_bend_force(Curve *curve, Point *point0, Point *point1,
float time) const
+{
+ float3 dir;
+ float3 edge = point1->cur.co - point0->cur.co;
+ normalize_v3_v3(dir, edge);
+ float3 dvel = point1->cur.vel - point0->cur.vel;
+
+ float3 bend_force = m_params.bend_stiffness * (edge -
point0->rest_bend);
+ float3 bend_damp = m_params.bend_damping * (dvel - dot_v3_v3(dvel, dir)
* dir);
+
+ return bend_force + bend_damp;
+}
+
+float3 Solver::calc_acceleration(Curve *curve, Point *point, float time,
Point::State &state) const
{
float3 acc = float3(0.0f, 0.0f, 0.0f);
acc = acc + m_forces.gravity;
- acc = acc - prev_stretch + stretch;
-
return acc;
}
@@ -187,7 +206,7 @@ void Solver::step(float timestep)
for (i = 0, curve = m_data->curves; i < totcurve; ++i, ++curve) {
int numpoints = curve->totpoints;
- float3 prev_stretch;
+ float3 stretch, prev_stretch, bend, prev_bend;
/* Root point animation */
k = 0;
@@ -197,20 +216,37 @@ void Solver::step(float timestep)
point->next.co = point->cur.co;
point->next.vel = float3(0.0f, 0.0f, 0.0f);
- float3 stretch = k < numpoints-1 ? calc_stretch(curve, point,
point+1, time) : float3(0.0f, 0.0f, 0.0f);
+ if (k < numpoints-1) {
+ stretch = calc_stretch_force(curve, point, point+1,
time);
+ bend = calc_bend_force(curve, point, point+1, time);
+ }
+ else {
+ stretch = float3(0.0f, 0.0f, 0.0f);
+ bend = float3(0.0f, 0.0f, 0.0f);
+ }
prev_stretch = stretch;
+ prev_bend = bend;
/* Integrate the remaining free points */
for (++k, ++point; k < numpoints; ++k, ++point) {
- float3 stretch = k < numpoints-1 ? calc_stretch(curve,
point, point+1, time) : float3(0.0f, 0.0f, 0.0f);
+ if (k < numpoints-1) {
+ stretch = calc_stretch_force(curve, point,
point+1, time);
+ bend = calc_bend_force(curve, point, point+1,
time);
+ }
+ else {
+ stretch = float3(0.0f, 0.0f, 0.0f);
+ bend = float3(0.0f, 0.0f, 0.0f);
+ }
- float3 acc = calc_acceleration(curve, point, time,
prev_stretch, stretch, point->cur);
+ float3 acc = calc_acceleration(curve, point, time,
point->cur);
+ acc = acc - prev_stretch + stretch - prev_bend + bend;
point->next.vel = point->cur.vel + acc * timestep;
float3 vel = calc_velocity(curve, point, time,
point->next);
point->next.co = point->cur.co + vel * timestep;
prev_stretch = stretch;
+ prev_bend = bend;
}
}
diff --git a/source/blender/hair/intern/HAIR_solver.h
b/source/blender/hair/intern/HAIR_solver.h
index 940d661..8ff5f11 100644
--- a/source/blender/hair/intern/HAIR_solver.h
+++ b/source/blender/hair/intern/HAIR_solver.h
@@ -77,8 +77,9 @@ public:
protected:
float3 calc_velocity(Curve *curve, Point *point, float time,
Point::State &state) const;
- float3 calc_acceleration(Curve *curve, Point *point, float time, float3
prev_stretch, float3 stretch, Point::State &state) const;
- float3 calc_stretch(Curve *curve, Point *point0, Point *point1, float
time) const;
+ float3 calc_acceleration(Curve *curve, Point *point, float time,
Point::State &state) const;
+ float3 calc_stretch_force(Curve *curve, Point *point0, Point *point1,
float time) const;
+ float3 calc_bend_force(Curve *curve, Point *point0, Point *point1,
float time) const;
private:
HairParams m_params;
diff --git a/source/blender/makesdna/DNA_hair_types.h
b/source/blender/makesdna/DNA_hair_types.h
index e5433e3..1f93807 100644
--- a/source/blender/makesdna/DNA_hair_types.h
+++ b/source/blender/makesdna/DNA_hair_types.h
@@ -49,7 +49,8 @@ typedef struct HairCurve {
typedef struct HairParams {
float stretch_stiffness;
float stretch_damping;
- int pad[2];
+ float bend_stiffness;
+ float bend_damping;
} HairParams;
typedef struct HairSystem {
diff --git a/source/blender/makesrna/intern/rna_hair.c
b/source/blender/makesrna/intern/rna_hair.c
index 64ee0d0..e5aab41 100644
--- a/source/blender/makesrna/intern/rna_hair.c
+++ b/source/blender/makesrna/intern/rna_hair.c
@@ -71,6 +71,18 @@ static void rna_def_hair_params(BlenderRNA *brna)
RNA_def_property_range(prop, 0.0f, 1.0e6f);
RNA_def_property_ui_range(prop, 0.0f, 1.0e5f, 0.1, 2);
RNA_def_property_ui_text(prop, "Stretch Damping", "");
+
+ prop = RNA_def_property(srna, "bend_stiffness", PROP_FLOAT,
PROP_FACTOR);
+ RNA_def_property_float_sdna(prop, NULL, "bend_stiffness");
+ RNA_def_property_range(prop, 0.0f, 1.0e9f);
+ RNA_def_property_ui_range(prop, 0.0f, 1.0e8f, 0.1, 2);
+ RNA_def_property_ui_text(prop, "Bend Stiffness", "");
+
+ prop = RNA_def_property(srna, "bend_damping", PROP_FLOAT, PROP_FACTOR);
+ RNA_def_property_float_sdna(prop, NULL, "bend_damping");
+ RNA_def_property_range(prop, 0.0f, 1.0e6f);
+ RNA_def_property_ui_range(prop, 0.0f, 1.0e5f, 0.1, 2);
+ RNA_def_property_ui_text(prop, "Bend Damping", "");
}
static void rna_def_hair_system(BlenderRNA *brna)
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