Include Rayleigh damping. Use struct instead of class. Update PinnedSoftBody test

examples/testbed/tests/pinned_softbody.h

@@ -32,7 +32,7 @@ public:
 		b3SoftBodyDef def;
 		def.mesh = &m_mesh;
 		def.density = 0.2f;
-		def.E = 100.0f;
+		def.E = 1000.0f;
 		def.nu = 0.33f;		
 		def.c_yield = 0.1f;
 		def.c_creep = 0.5f;
@@ -40,6 +40,12 @@ public:
 
 		m_body = new b3SoftBody(def);
 
+		for (u32 i = 0; i < m_mesh.vertexCount; ++i)
+		{
+			b3SoftBodyNode* n = m_body->GetVertexNode(i);
+			n->SetDamping(0.2f);
+		}
+
 		u32 pinIndex = ~0;
 		float32 pinDot = -B3_MAX_FLOAT;
 		for (u32 i = 0; i < m_mesh.vertexCount; ++i)

include/bounce/softbody/softbody.h

@@ -26,7 +26,8 @@ class b3World;
 
 struct b3SoftBodyMesh;
 
-class b3SoftBodyNode;
+struct b3SoftBodyNode;
+struct b3SoftBodyElement;
 
 struct b3RayCastInput;
 struct b3RayCastOutput;

include/bounce/softbody/softbody_contact_solver.h

@@ -24,10 +24,10 @@
 
 class b3StackAllocator;
 
-class b3SoftBodyNode;
+struct b3SoftBodyNode;
 class b3Body;
 
-class b3NodeBodyContact;
+struct b3NodeBodyContact;
 
 struct b3DenseVec3;
 

include/bounce/softbody/softbody_node.h

@@ -25,15 +25,11 @@
 
 class b3Shape;
 class b3SoftBody;
-class b3SoftBodyNode;
+struct b3SoftBodyNode;
 
 // A contact between a node and a body
-class b3NodeBodyContact
+struct b3NodeBodyContact
 {
-public:
-	b3NodeBodyContact() { }
-	~b3NodeBodyContact() { }
-
 	b3SoftBodyNode* n1;
 	b3Shape* s2;
 
@@ -81,7 +77,7 @@ enum b3SoftBodyNodeType
 };
 
 // A soft body node.
-class b3SoftBodyNode 
+struct b3SoftBodyNode 
 {
 public:
 	// Set the node type.
@@ -110,6 +106,12 @@ public:
 	// Get the node mass.
 	float32 GetMass() const;
 
+	// Set the node damping.
+	void SetDamping(float32 damping);
+
+	// Get the node damping.
+	float32 GetDamping() const;
+
 	// Set the node radius.
 	void SetRadius(float32 radius);
 	
@@ -151,6 +153,9 @@ private:
 	// Inverse mass
 	float32 m_invMass;
 
+	// Damping
+	float32 m_damping;
+
 	// Radius
 	float32 m_radius;
 
@@ -227,6 +232,16 @@ inline float32 b3SoftBodyNode::GetMass() const
 	return m_mass;
 }
 
+inline void b3SoftBodyNode::SetDamping(float32 damping)
+{
+	m_damping = damping;
+}
+
+inline float32 b3SoftBodyNode::GetDamping() const
+{
+	return m_damping;
+}
+
 inline void b3SoftBodyNode::SetRadius(float32 radius)
 {
 	m_radius = radius;

include/bounce/softbody/softbody_solver.h

@@ -27,10 +27,10 @@ class b3StackAllocator;
 class b3SoftBody;
 class b3SoftBodyMesh;
 
-class b3SoftBodyNode;
+struct b3SoftBodyNode;
 struct b3SoftBodyElement;
 
-class b3NodeBodyContact;
+struct b3NodeBodyContact;
 
 struct b3SoftBodySolverDef
 {

src/bounce/softbody/softbody.cpp

@@ -465,6 +465,7 @@ b3SoftBody::b3SoftBody(const b3SoftBodyDef& def)
 		n->m_force.SetZero();
 		n->m_mass = 0.0f;
 		n->m_invMass = 0.0f;
+		n->m_damping = 0.0f;
 		n->m_radius = 0.0f;
 		n->m_friction = 0.0f;
 		n->m_userData = nullptr;

src/bounce/softbody/softbody_solver.cpp

@@ -195,6 +195,7 @@ void b3SoftBodySolver::Solve(float32 dt, const b3Vec3& gravity, u32 velocityIter
 	float32 inv_h = 1.0f / h;
 
 	b3SparseMat33 M(m_mesh->vertexCount);
+	b3SparseMat33 C(m_mesh->vertexCount);
 	b3DenseVec3 x(m_mesh->vertexCount);
 	b3DenseVec3 p(m_mesh->vertexCount);
 	b3DenseVec3 v(m_mesh->vertexCount);
@@ -207,6 +208,12 @@ void b3SoftBodySolver::Solve(float32 dt, const b3Vec3& gravity, u32 velocityIter
 		b3SoftBodyNode* n = m_nodes + i;
 
 		M(i, i) = b3Diagonal(n->m_mass);
+		
+		// Rayleigh damping 
+		// C = alpha * M + beta * K
+		// Here the stiffness coefficient beta is zero
+		C(i, i) = b3Diagonal(n->m_damping * n->m_mass);
+		
 		x[i] = m_mesh->vertices[i];
 		p[i] = n->m_position;
 		v[i] = n->m_velocity;
@@ -369,9 +376,8 @@ void b3SoftBodySolver::Solve(float32 dt, const b3Vec3& gravity, u32 velocityIter
 
 	f0 = -f0;
 
-	b3SparseMat33 A = M + h * h * K;
+	b3SparseMat33 A = M + h * C + h * h * K;
 
-	//b3DenseVec3 b = M * v - h * (K * p + f0 + f_plastic - fe);
 	b3DenseVec3 b = M * v - h * (K * p + f0 - (f_plastic + fe));
 
 	// Solve Ax = b