From 8876429edda44b542c8dc30ea6a9a7b9d88bc451 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lukas=20T=C3=B6nne?= <lukas.toenne@gmail.com>
Date: Tue, 16 Sep 2014 20:44:25 +0200
Subject: Added back the velocity smoothing implementation.

This is now also decoupled from the internal solver data. The grid is
created as an opaque structure, filled with vertex or collider data
(todo), and then forces can be calculated by interpolating the grid at
random locations. These forces and derivatives are then fed into the
solver.
---
 source/blender/physics/intern/BPH_mass_spring.cpp | 61 ++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 2 deletions(-)

(limited to 'source/blender/physics/intern/BPH_mass_spring.cpp')

diff --git a/source/blender/physics/intern/BPH_mass_spring.cpp b/source/blender/physics/intern/BPH_mass_spring.cpp
index 1c45e1ed1f8..568aea6abe3 100644
--- a/source/blender/physics/intern/BPH_mass_spring.cpp
+++ b/source/blender/physics/intern/BPH_mass_spring.cpp
@@ -386,6 +386,64 @@ BLI_INLINE void cloth_calc_spring_force(ClothModifierData *clmd, ClothSpring *s,
 	}
 }
 
+static void hair_get_boundbox(ClothModifierData *clmd, float gmin[3], float gmax[3])
+{
+	Cloth *cloth = clmd->clothObject;
+	Implicit_Data *data = cloth->implicit;
+	unsigned int numverts = cloth->numverts;
+	int i;
+	
+	INIT_MINMAX(gmin, gmax);
+	for (i = 0; i < numverts; i++) {
+		float x[3];
+		BPH_mass_spring_get_motion_state(data, i, x, NULL);
+		DO_MINMAX(x, gmin, gmax);
+	}
+}
+
+static void cloth_calc_volume_force(ClothModifierData *clmd)
+{
+	ClothSimSettings *parms = clmd->sim_parms;
+	Cloth *cloth = clmd->clothObject;
+	Implicit_Data *data = cloth->implicit;
+	int numverts = cloth->numverts;
+	
+	/* 2.0f is an experimental value that seems to give good results */
+	float smoothfac = 2.0f * parms->velocity_smooth;
+	float collfac = 2.0f * parms->collider_friction;
+	float pressfac = parms->pressure;
+	float minpress = parms->pressure_threshold;
+	float gmin[3], gmax[3];
+	int i;
+	
+	hair_get_boundbox(clmd, gmin, gmax);
+	
+	/* gather velocities & density */
+	if (smoothfac > 0.0f || pressfac > 0.0f) {
+		HairVertexGrid *vertex_grid = BPH_hair_volume_create_vertex_grid(gmin, gmax);
+		
+		for (i = 0; i < numverts; i++) {
+			float x[3], v[3];
+			
+			BPH_mass_spring_get_motion_state(data, i, x, v);
+			BPH_hair_volume_add_vertex(vertex_grid, x, v);
+		}
+		BPH_hair_volume_normalize_vertex_grid(vertex_grid);
+		
+		for (i = 0; i < numverts; i++) {
+			float x[3], v[3], f[3], dfdx[3][3], dfdv[3][3];
+			
+			/* calculate volumetric forces */
+			BPH_mass_spring_get_motion_state(data, i, x, v);
+			BPH_hair_volume_vertex_grid_forces(vertex_grid, x, v, smoothfac, pressfac, minpress, f, dfdx, dfdv);
+			/* apply on hair data */
+			BPH_mass_spring_force_extern(data, i, f, dfdx, dfdv);
+		}
+		
+		BPH_hair_volume_free_vertex_grid(vertex_grid);
+	}
+}
+
 static void cloth_calc_force(ClothModifierData *clmd, float UNUSED(frame), ListBase *effectors, float time)
 {
 	/* Collect forces and derivatives:  F, dFdX, dFdV */
@@ -409,8 +467,7 @@ static void cloth_calc_force(ClothModifierData *clmd, float UNUSED(frame), ListB
 	BPH_mass_spring_force_gravity(data, gravity);
 #endif
 
-	// XXX TODO
-//	hair_volume_forces(clmd, lF, lX, lV, numverts);
+	cloth_calc_volume_force(clmd);
 
 #ifdef CLOTH_FORCE_DRAG
 	BPH_mass_spring_force_drag(data, drag);
-- 
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