kinematic cloth

include/bounce/dynamics/cloth/spring_cloth.h

@@ -22,6 +22,7 @@
 #include <bounce/common/math/mat33.h>
 #include <bounce/common/template/array.h>
 
+// Number of maximum shapes per cloth.
 #define B3_CLOTH_SHAPE_CAPACITY 32
 
 class b3StackAllocator;
@@ -63,6 +64,8 @@ struct b3SpringClothDef
 	float32 kd;
 	
 	// Mass radius
+	// Typically this is value is small and is intended for correcting visual artifacts when 
+	// the cloth is colliding against a solid.
 	float32 r;
 	
 	// Acceleration due to gravity (m/s^2)
@@ -97,10 +100,12 @@ struct b3Spring
 };
 
 // Static masses have zero mass and velocity, and therefore they can't move.
+// Kinematic masses are't moved by external and internal forces but can be moved by contact forces.
 // Dynamic masses have non-zero mass and can move due to internal and external forces.
 enum class b3MassType : u32
 {
 	e_staticMass,
+	e_kinematicMass,
 	e_dynamicMass
 };
 
@@ -140,6 +145,9 @@ public:
 	// Units are m/s^2.
 	void SetGravity(const b3Vec3& gravity);
 
+	// Return the number of masses in this cloth.
+	u32 GetMassCount() const;
+
 	// Return the gravitational acceleration applied to this cloth.
 	const b3Vec3& GetGravity() const;
 
@@ -152,11 +160,17 @@ public:
 	// Set the position of a given point mass.
 	// This function will have effect on the position of the point mass 
 	// after performing a time step.
-	void SetPosition(u32 i, const b3Vec3& translation);
+	void SetPosition(u32 i, const b3Vec3& position);
 
 	// Return the position of a given point mass.
 	const b3Vec3& GetPosition(u32 i) const;
 
+	// Set the velocity of a given point mass.
+	void SetVelocity(u32 i, const b3Vec3& velocity);
+
+	// Return the velocity of a given point mass.
+	const b3Vec3& GetVelocity(u32 i) const;
+	
 	// Apply a force to a given point mass.
 	void ApplyForce(u32 i, const b3Vec3& force);
 
@@ -237,6 +251,11 @@ inline void b3SpringCloth::SetGravity(const b3Vec3& gravity)
 	m_gravity = gravity;
 }
 
+inline u32 b3SpringCloth::GetMassCount() const
+{
+	return m_massCount;
+}
+
 inline b3MassType b3SpringCloth::GetType(u32 i) const
 {
 	B3_ASSERT(i < m_massCount);
@@ -246,6 +265,7 @@ inline b3MassType b3SpringCloth::GetType(u32 i) const
 inline void b3SpringCloth::SetType(u32 i, b3MassType type)
 {
 	B3_ASSERT(i < m_massCount);
+	
 	if (m_types[i] == type)
 	{
 		return;
@@ -276,6 +296,24 @@ inline const b3Vec3& b3SpringCloth::GetPosition(u32 i) const
 	return m_x[i];
 }
 
+inline void b3SpringCloth::SetVelocity(u32 i, const b3Vec3& velocity)
+{
+	B3_ASSERT(i < m_massCount);
+	
+	if (m_types[i] == b3MassType::e_staticMass)
+	{
+		return;
+	}
+
+	m_v[i] = velocity;
+}
+
+inline const b3Vec3& b3SpringCloth::GetVelocity(u32 i) const
+{
+	B3_ASSERT(i < m_massCount);
+	return m_v[i];
+}
+
 inline void b3SpringCloth::ApplyForce(u32 i, const b3Vec3& force)
 {
 	B3_ASSERT(i < m_massCount);

src/bounce/dynamics/cloth/spring_cloth.cpp

@@ -400,7 +400,7 @@ void b3SpringCloth::GetTension(b3Array<b3Vec3>& T) const
 
 	for (u32 i = 0; i < T.Count(); ++i)
 	{
-		if (m_types[i] == b3MassType::e_staticMass)
+		if (m_types[i] != b3MassType::e_dynamicMass)
 		{
 			T[i].SetZero();
 		}
@@ -677,11 +677,26 @@ void b3SpringCloth::Draw() const
 
 	for (u32 i = 0; i < m->vertexCount; ++i)
 	{
+		if (m_types[i] == b3MassType::e_staticMass)
+		{
+			b3Draw_draw->DrawPoint(m_x[i], 4.0f, b3Color_white);
+		}
+		
+		if (m_types[i] == b3MassType::e_kinematicMass)
+		{
+			b3Draw_draw->DrawPoint(m_x[i], 4.0f, b3Color_blue);
+		}
+		
+		if (m_types[i] == b3MassType::e_dynamicMass)
+		{
+			b3Draw_draw->DrawPoint(m_x[i], 4.0f, b3Color_green);
+		}
+
 		b3MassContact* c = m_contacts + i;
 		
 		if (c->lockN)
 		{
-			b3Draw_draw->DrawPoint(m_x[i], 6.0f, b3Color_green);
+			b3Draw_draw->DrawPoint(m_x[i], 6.0f, b3Color_yellow);
 			
 			b3Draw_draw->DrawSegment(m_x[i], m_x[i] + c->n, b3Color_yellow);
 			

src/bounce/dynamics/cloth/spring_solver.cpp

@@ -103,8 +103,11 @@ void b3SpringSolver::Solve(b3DenseVec3& f)
 
 		// Update state
 		for (u32 i = 0; i < m_massCount; ++i)
+		{
+			if (m_types[i] == b3MassType::e_dynamicMass)
 			{
 				m_v[i] += x[i];
+			}
 
 			// dx = h * (v0 + dv) + y = h * v1 + y
 			m_x[i] += m_h * m_v[i] + m_y[i];
@@ -365,54 +368,44 @@ void b3SpringSolver::Compute_S(b3Mat33* out)
 {
 	for (u32 i = 0; i < m_massCount; ++i)
 	{
-		switch (m_types[i])
-		{
-		case b3MassType::e_staticMass:
+		out[i].SetIdentity();
+
+		if (m_types[i] == b3MassType::e_staticMass)
 		{
 			out[i].SetZero();
-			break;
+			continue;
 		}
-		case b3MassType::e_dynamicMass:
+
+		b3MassContact* c = m_contacts + i;
+
+		if (c->lockN == true)
 		{
-			if (m_contacts[i].lockN == true)
-			{
-				b3Vec3 n = m_contacts[i].n;
+			b3Vec3 n = c->n;
 
 			b3Mat33 S = b3Mat33_identity - b3Outer(n, n);
 
-				if (m_contacts[i].lockT1 == true && m_contacts[i].lockT2 == true)
+			if (c->lockT1 == true && c->lockT2 == true)
 			{
 				S.SetZero();
 			}
 			else
 			{
-					if (m_contacts[i].lockT1 == true)
+				if (c->lockT1 == true)
 				{
-						b3Vec3 t1 = m_contacts[i].t1;
+					b3Vec3 t1 = c->t1;
 
 					S -= b3Outer(t1, t1);
 				}
 
-					if (m_contacts[i].lockT2 == true)
+				if (c->lockT2 == true)
 				{
-						b3Vec3 t2 = m_contacts[i].t2;
+					b3Vec3 t2 = c->t2;
 
 					S -= b3Outer(t2, t2);
 				}
 			}
 
 			out[i] = S;
-				break;
-			}
-
-			out[i].SetIdentity();
-			break;
-		}
-		default:
-		{
-			B3_ASSERT(false);
-			break;
-		}
 		}
 	}
 }