Store material parameters inside elements

include/bounce/softbody/softbody.h

@@ -43,6 +43,13 @@ struct b3SoftBodyRayCastSingleOutput
 // Soft body tetrahedron element
 struct b3SoftBodyElement
 {
+	float32 E;
+	float32 nu;
+
+	float32 c_yield;
+	float32 c_creep;
+	float32 c_max;
+
 	b3Mat33 K[16]; // 12 x 12
 	b3Mat33 invE;
 	b3Quat q;
@@ -60,6 +67,7 @@ struct b3SoftBodyTriangle
 
 // Soft body definition
 // This requires defining a soft body mesh which is typically bound to a render mesh
+// and some uniform material parameters.
 struct b3SoftBodyDef
 {
 	b3SoftBodyDef()
@@ -130,6 +138,9 @@ public:
 	// Return the node associated with the given vertex.
 	b3SoftBodyNode* GetVertexNode(u32 i);
 
+	// Return the element associated with the given tetrahedron.
+	b3SoftBodyElement* GetTetrahedronElement(u32 i);
+
 	// Return the kinetic (or dynamic) energy in this system.
 	float32 GetEnergy() const;
 
@@ -162,21 +173,6 @@ private:
 	// Soft body density
 	float32 m_density;
 
-	// Material Young's modulus
-	float32 m_E;
-
-	// Material poisson ratio
-	float32 m_nu;
-
-	// Material yield
-	float32 m_c_yield;
-
-	// Material creep rate
-	float32 m_c_creep;
-
-	// Material maximum plastic strain
-	float32 m_c_max;
-
 	// Soft body nodes
 	b3SoftBodyNode* m_nodes;
 

src/bounce/softbody/softbody.cpp

@@ -450,11 +450,6 @@ b3SoftBody::b3SoftBody(const b3SoftBodyDef& def)
 
 	m_mesh = def.mesh;
 	m_density = def.density;
-	m_E = def.E;
-	m_nu = def.nu;
-	m_c_yield = def.c_yield;
-	m_c_creep = def.c_creep;
-	m_c_max = def.c_max;
 	m_gravity.SetZero();
 	m_world = nullptr;
 	m_contactManager.m_body = this;
@@ -495,6 +490,12 @@ b3SoftBody::b3SoftBody(const b3SoftBodyDef& def)
 	{
 		b3SoftBodyMeshTetrahedron* mt = m->tetrahedrons + ei;
 		b3SoftBodyElement* e = m_elements + ei;
+		
+		e->E = def.E;
+		e->nu = def.nu;
+		e->c_yield = def.c_yield;
+		e->c_creep = def.c_creep;
+		e->c_max = def.c_max;
 
 		u32 v1 = mt->v1;
 		u32 v2 = mt->v2;
@@ -520,7 +521,7 @@ b3SoftBody::b3SoftBody(const b3SoftBodyDef& def)
 
 		// 6 x 6
 		float32 D[36];
-		b3ComputeD(D, m_E, m_nu);
+		b3ComputeD(D, e->E, e->nu);
 
 		// 6 x 12
 		float32* B = e->B;
@@ -658,6 +659,12 @@ b3SoftBodyNode* b3SoftBody::GetVertexNode(u32 i)
 	return m_nodes + i;
 }
 
+b3SoftBodyElement* b3SoftBody::GetTetrahedronElement(u32 i)
+{
+	B3_ASSERT(i < m_mesh->tetrahedronCount);
+	return m_elements + i;
+}
+
 float32 b3SoftBody::GetEnergy() const
 {
 	float32 E = 0.0f;

src/bounce/softbody/softbody_force_solver.cpp

@@ -345,9 +345,9 @@ void b3SoftBodyForceSolver::Solve(float32 dt, const b3Vec3& gravity)
 		}
 
 		float32 len_epsilon_elastic = b3Length(epsilon_elastic, 6);
-		if (len_epsilon_elastic > m_body->m_c_yield)
+		if (len_epsilon_elastic > e->c_yield)
 		{
-			float32 amount = h * b3Min(m_body->m_c_creep, inv_h);
+			float32 amount = h * b3Min(e->c_creep, inv_h);
 			for (u32 i = 0; i < 6; ++i)
 			{
 				epsilon_plastic[i] += amount * epsilon_elastic[i];
@@ -355,9 +355,9 @@ void b3SoftBodyForceSolver::Solve(float32 dt, const b3Vec3& gravity)
 		}
 
 		float32 len_epsilon_plastic = b3Length(epsilon_plastic, 6);
-		if (len_epsilon_plastic > m_body->m_c_max)
+		if (len_epsilon_plastic > e->c_max)
 		{
-			float32 scale = m_body->m_c_max / len_epsilon_plastic;
+			float32 scale = e->c_max / len_epsilon_plastic;
 			for (u32 i = 0; i < 6; ++i)
 			{
 				epsilon_plastic[i] *= scale;