[Bf-blender-cvs] [3c15410] hair_system: Simple air drag term for hair.

[Lukas Tönne]

Commit: 3c154105ce80c6a88071fe6369278aa4c89bcc6a
Author: Lukas Tönne
Date:   Fri Aug 8 13:46:19 2014 +0200
Branches: hair_system
https://developer.blender.org/rB3c154105ce80c6a88071fe6369278aa4c89bcc6a

Simple air drag term for hair.

This avoids ceaseless movement and is physically quite plausible. It
doesn't replace real hair-hair collision though.

===================================================================

M       release/scripts/startup/bl_ui/properties_data_modifier.py
M       source/blender/hair/intern/HAIR_solver.cpp
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 837c86a..681d39e 100644
--- a/release/scripts/startup/bl_ui/properties_data_modifier.py
+++ b/release/scripts/startup/bl_ui/properties_data_modifier.py
@@ -1249,8 +1249,9 @@ class DATA_PT_modifiers(ModifierButtonsPanel, Panel):
         row = col.row()
         col2 = row.column()
         col2.prop(params, "restitution")
-        col2 = row.column()
         col2.prop(params, "friction")
+        col2 = row.column()
+        col2.prop(params, "drag")
         
         col.separator()
         
diff --git a/source/blender/hair/intern/HAIR_solver.cpp 
b/source/blender/hair/intern/HAIR_solver.cpp
index 3358f47..69372a6 100644
--- a/source/blender/hair/intern/HAIR_solver.cpp
+++ b/source/blender/hair/intern/HAIR_solver.cpp
@@ -286,7 +286,9 @@ static void do_external_forces(const HairParams &params, 
const SolverForces &for
 {
        float3 acc = float3(0.0f, 0.0f, 0.0f);
        
-       acc = acc + forces.gravity;
+       float3 drag = - params.drag * point0->cur.vel;
+       
+       acc = acc + forces.gravity + drag;
        
        force = acc;
 }
diff --git a/source/blender/makesdna/DNA_hair_types.h 
b/source/blender/makesdna/DNA_hair_types.h
index b4b210d..d9dc77d 100644
--- a/source/blender/makesdna/DNA_hair_types.h
+++ b/source/blender/makesdna/DNA_hair_types.h
@@ -62,11 +62,11 @@ typedef struct HairParams {
        float bend_damping;
        float bend_smoothing;
        
+       float drag;
+       
        /* collision settings */
        float restitution;
        float friction;
-       
-       int pad;
 } HairParams;
 
 typedef struct HairSystem {
diff --git a/source/blender/makesrna/intern/rna_hair.c 
b/source/blender/makesrna/intern/rna_hair.c
index 90b9184..7495996 100644
--- a/source/blender/makesrna/intern/rna_hair.c
+++ b/source/blender/makesrna/intern/rna_hair.c
@@ -106,6 +106,13 @@ static void rna_def_hair_params(BlenderRNA *brna)
        RNA_def_property_ui_range(prop, 0.0f, 8.0f, 0.1, 2);
        RNA_def_property_ui_text(prop, "Bend Smoothing", "Smoothing amount to 
avoid rotation of hair curls");
 
+       prop = RNA_def_property(srna, "drag", PROP_FLOAT, PROP_FACTOR);
+       RNA_def_property_float_sdna(prop, NULL, "drag");
+       RNA_def_property_range(prop, 0.0f, FLT_MAX);
+       RNA_def_property_ui_range(prop, 0.0f, 1.0f, 0.01f, 3);
+       RNA_def_property_float_default(prop, 0.0f);
+       RNA_def_property_ui_text(prop, "Drag", "Air drag factor");
+
        prop = RNA_def_property(srna, "friction", PROP_FLOAT, PROP_FACTOR);
        RNA_def_property_float_sdna(prop, NULL, "friction");
        RNA_def_property_range(prop, 0.0f, FLT_MAX);

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