fix midpoint

Reviewed-on: #9

Simulations/MassSpringSystemSimulator.cpp

@@ -1,18 +1,8 @@
 #include "MassSpringSystemSimulator.h"
+#include <stdio.h>
 
 MassSpringSystemSimulator::MassSpringSystemSimulator()
 {
-	m_iTestCase = 0;
-	m_fMass = 10;
-	m_fStiffness = 40;
-	int m_iIntegrater = 0;
-
-
-	//Test only
-	auto first = addMassPoint(Vec3(0, 0, 1), Vec3(0, 0, 0), true);
-	auto second = addMassPoint(Vec3(0, 0, 0), Vec3(0, 0, 0), true);
-	addSpring(first, second, 2.0);
-
 }
 
 const char* MassSpringSystemSimulator::getTestCasesStr()
@@ -25,13 +15,14 @@ void MassSpringSystemSimulator::initUI(DrawingUtilitiesClass* DUC)
 	this->DUC = DUC;
 	switch (m_iTestCase)
 	{
-	case 0:break;
+		case 0:
-	case 1:
+			break;
-	
+		case 1:
-		break;
+			break;
-	case 2:
+		case 2:
-		break;
+			break;
-	default:break;
+		default:
+			break;
 	}
 }
 
@@ -40,10 +31,11 @@ void MassSpringSystemSimulator::reset()
 	m_mouse.x = m_mouse.y = 0;
 	m_trackmouse.x = m_trackmouse.y = 0;
 	m_oldtrackmouse.x = m_oldtrackmouse.y = 0;
+
+	springs.clear();
+	masspoints.clear();
 }
 
-
-
 void MassSpringSystemSimulator::drawFrame(ID3D11DeviceContext* pd3dImmediateContext)
 {
 	
@@ -70,26 +62,91 @@ void MassSpringSystemSimulator::drawFrame(ID3D11DeviceContext* pd3dImmediateCont
 void MassSpringSystemSimulator::notifyCaseChanged(int testCase)
 {
 	m_iTestCase = testCase;
+	system("cls");
+	reset();
+
 	switch (m_iTestCase)
 	{
-	case 0:
+	case 0: {
-		cout << "Demo1 !\n";
+		cout << "Demo 1 !\n";
+		setMass(10);
+		setStiffness(40);
 
-//simulateTimestep(1);
+		int first = addMassPoint(Vec3(0, 0, 0), Vec3(-1, 0, 0), true);
+		int second = addMassPoint(Vec3(0, 2, 0), Vec3(1, 0, 0), true);
+
+		addSpring(first, second, 1);
+		cout << "\t -- INITIAL --\n";
+		printSpring(springs.at(0));
+		cout << "--------------------------------------------------" << std::endl;
+
+		//calculate Euler for one step and print results
+		setIntegrator(EULER);
+		cout << "\n\n\t -- EULER RESULT --\n";
+		simulateTimestep(1);
+		printSpring(springs.at(0));
+
+		cout << "--------------------------------------------------" << std::endl;
+
+		reset();
+		first = addMassPoint(Vec3(0, 0, 0), Vec3(-1, 0, 0), true);
+		second = addMassPoint(Vec3(0, 2, 0), Vec3(1, 0, 0), true);
+
+		addSpring(first, second, 1);
+
+		//calculate Midpoint for one step and print results
+		setIntegrator(MIDPOINT);
+		cout << "\n\n\t -- MIDPOINT RESULT --\n";
+		simulateTimestep(1);
+		printSpring(springs.at(0));
+		break;
+	}
+	
+	case 1: {
+		cout << "Demo 2 !\n";
+		reset();
+		int first = addMassPoint(Vec3(0, 0, 0), Vec3(-1, 0, 0), true);
+		int second = addMassPoint(Vec3(0, 2, 0), Vec3(1, 0, 0), true);
+		addSpring(first, second, 1.0);
+
+		cout << "\t -- INITIAL --\n";
+		printSpring(springs.at(0));
+
+		cout << "--------------------------------------------------" << std::endl;
+
+		//calculate Euler for a timestep of 0.005 and print results
+		setIntegrator(EULER);
+		cout << "\n\n\t -- EULER RESULT--\n";
+		simulateTimestep(0.005);
+		printSpring(springs.at(0));
 
 		break;
-	case 1:
+	}
-		cout << "Demo2 \n";
+
-		//m_iNumSpheres = 100;
+	case 2: {
-		//m_fSphereSize = 0.05f;
+		cout << "Demo 3 !\n";
+		reset();
+		int first = addMassPoint(Vec3(0, 0, 0), Vec3(-1, 0, 0), true);
+		int second = addMassPoint(Vec3(0, 2, 0), Vec3(1, 0, 0), true);
+		addSpring(first, second, 1.0);
+
+		cout << "\t -- INITIAL --\n";
+		printSpring(springs.at(0));
+
+		cout << "--------------------------------------------------" << std::endl;
+
+		//calculate Midpoint for a timestep of 0.005 and print results
+		setIntegrator(MIDPOINT);
+		cout << "\n\n\t -- MIDPOINT RESULT --\n";
+		simulateTimestep(0.005);
+		printSpring(springs.at(0));
 		break;
-	case 2:
+	}
-		cout << "Demo3 !\n";
+	case 3: {
-		break;
-	case 3:
 		cout << "Demo 4 !\n";
+		break;
+	}
 	default:
-		//cout << "Demo4 !\n";
 		break;
 	}
 }
@@ -117,25 +174,28 @@ void MassSpringSystemSimulator::externalForcesCalculations(float timeElapsed)
 
 }
 
-
-
 void MassSpringSystemSimulator::simulateTimestep(float timeStep)
 {
 	//update current setup for each frame
-	switch (m_iTestCase) {
+	for (size_t i = 0; i < springs.size(); i++) {
-	case 0:
+		auto sp = springs.at(i);
-		//update the masspoint
+		if (!sp.isValid())
-		cout << "Euler \n";
+		{
+			springs.erase(springs.begin() + i);
+			continue;
+		}
+
+		if (m_iIntegrator == EULER) {
+
+			Euler(sp, timeStep);
+		}
+		else if (m_iIntegrator == MIDPOINT) {
+			Midpoint(sp, timeStep);
+		}
+		else if (m_iIntegrator == LEAPFROG) {
+			//TODO: Add Leapfrog
+		}
 
-		cout << "Midpoint\n";
-		break;
-	case 1:cout << "demo 2 \n";
-		break;
-	case 2:cout << "demo 3\n";
-		break;
-	case 3: cout << "demo 4\n";
-		break;
-	default: break;
 	}
 }
 
@@ -216,5 +276,106 @@ Vec3 MassSpringSystemSimulator::getVelocityOfMassPoint(int index)
 
 void MassSpringSystemSimulator::applyExternalForce(Vec3 force)
 {
-
+	//eine Vorstellung: for all Masspoints, update force
+}
+
+float MassSpringSystemSimulator::LengthCalculator(Vec3 vector) 
+{
+	//wurzel aus Vektor
+	float length = sqrt(vector.x * vector.x + vector.y * vector.y + vector.z * vector.z);
+	return length;
+}
+
+Vec3 MassSpringSystemSimulator::calculatePositionTimestepEuler(Vec3 oldPosition, float timestep, Vec3 velocity)
+{
+	return oldPosition + timestep * velocity;
+}
+
+Vec3 MassSpringSystemSimulator::calculateVelocityTimestepEuler(Vec3 oldVelocity, float timestep, Vec3 acceleration)
+{
+	return oldVelocity + acceleration * timestep;
+}
+
+Vec3 MassSpringSystemSimulator::calculateAcceleration(Vec3 force, float mass)
+{
+	return force / mass;
+}
+
+void MassSpringSystemSimulator::Midpoint(Spring& spring, float timestep) {
+	//here some implementation about Midpoint
+	auto massPoint1 = spring.mp1.lock();
+	auto massPoint2 = spring.mp2.lock();
+
+	Vec3 PosVector = massPoint1->position - massPoint2->position;
+	//Abstand ausrechnen
+	float length = sqrtf(PosVector.x * PosVector.x + PosVector.y * PosVector.y + PosVector.z * PosVector.z);
+	//normalize
+	Vec3 normal = PosVector / length;
+
+	//Midpoint calculator
+	std::tuple<Vec3, Vec3> midpointStep1 = MidPointHalfStep(timestep * .5, spring, massPoint1->position, massPoint1->velocity, normal, length);
+	std::tuple<Vec3, Vec3> midpointStep2 = MidPointHalfStep(timestep * .5, spring, massPoint2->position, massPoint2->velocity, -normal, length);
+
+	Vec3 newPosVector = std::get<0>(midpointStep1) - std::get<0>(midpointStep2);
+	float newLength = sqrtf(newPosVector.x * newPosVector.x + newPosVector.y * newPosVector.y + newPosVector.z * newPosVector.z);
+	Vec3 newNormal = newPosVector / newLength;
+
+	std::tuple<Vec3, Vec3> midpoint1 = MidPointStep(timestep, spring, massPoint1->position, massPoint1->velocity, std::get<1>(midpointStep1), newNormal, newLength);
+	std::tuple<Vec3, Vec3> midpoint2 = MidPointStep(timestep, spring, massPoint2->position, massPoint2->velocity, std::get<1>(midpointStep2), -newNormal, newLength);
+	
+	massPoint1->position = std::get<0>(midpoint1);
+	massPoint1->velocity = std::get<1>(midpoint1);
+	massPoint2->position = std::get<0>(midpoint2);
+	massPoint2->velocity = std::get<1>(midpoint2);
+}
+
+std::tuple<Vec3, Vec3> MassSpringSystemSimulator::MidPointHalfStep(double timestep, const Spring& spring, Vec3 position, Vec3 velocity, Vec3 normal, double length)
+{
+	return MidPointStep(timestep, spring, position, velocity, velocity, normal, length);
+}
+
+
+std::tuple<Vec3, Vec3> MassSpringSystemSimulator::MidPointStep(double timestep, const Spring& spring, Vec3 position, Vec3 oldVelo,Vec3 velocity, Vec3 normal, double length)
+{
+	auto force = -m_fStiffness * (length - spring.initialLength) * normal;
+	auto acc = calculateAcceleration(force, m_fMass);
+	auto pos = position + timestep * velocity;
+	auto vel = oldVelo + timestep * acc;
+	return std::tuple<Vec3, Vec3>(pos, vel);
+}
+
+void MassSpringSystemSimulator::Euler(Spring& spring, float timestep)
+{
+	auto massPoint1 = spring.mp1.lock();
+	auto massPoint2 = spring.mp2.lock();
+
+	//take old position and send to calculatePositionTimestepEuler
+	auto PosVector = massPoint1->position - massPoint2->position;
+	auto lengthVector = sqrt(PosVector.x * PosVector.x + PosVector.y * PosVector.y + PosVector.z * PosVector.z);
+	auto normalized = PosVector / lengthVector;
+
+	// Actual Calculation
+	// Force of spring is -k * (l - L) * normalizedVector [for P2 we can take -F1)
+	auto force = -m_fStiffness * (lengthVector - spring.initialLength) * normalized;
+	auto foreP2 = -1 * force;
+	auto veloc = calculateVelocityTimestepEuler(massPoint1->velocity, timestep, calculateAcceleration(force, m_fMass));
+	auto pos = calculatePositionTimestepEuler(massPoint1->position, timestep, massPoint1->velocity);
+
+	auto veloc2 = calculateVelocityTimestepEuler(massPoint2->velocity, timestep, calculateAcceleration(foreP2, m_fMass));
+	auto pos2 = calculatePositionTimestepEuler(massPoint2->position, timestep, massPoint2->velocity);
+
+	// Update Positions and Velocity
+	massPoint1->position = pos;
+	massPoint1->velocity = veloc;
+
+	massPoint2->position = pos2;
+	massPoint2->velocity = veloc2;
+}
+
+void MassSpringSystemSimulator::printSpring(const Spring& spring)
+{
+	auto mp1 = spring.mp1.lock();
+	auto mp2 = spring.mp2.lock();
+	printf("Masspoint 1:\nPosition: %s \nVelocity: %s\n\n", mp1->position.toString().c_str(), mp1->velocity.toString().c_str());
+	printf("Masspoint 2:\nPosition: %s \nVelocity: %s\n", mp2->position.toString().c_str(), mp2->velocity.toString().c_str());
 }

Simulations/MassSpringSystemSimulator.h

@@ -39,6 +39,18 @@ public:
 	Vec3 getVelocityOfMassPoint(int index);
 	void applyExternalForce(Vec3 force);
 
+	void Midpoint(Spring& spring, float timestep);
+	std::tuple<Vec3, Vec3> MidPointHalfStep(double timestep, const Spring& spring, Vec3 position, Vec3 velocity, Vec3 normal, double length);
+	std::tuple<Vec3, Vec3> MassSpringSystemSimulator::MidPointStep(double timestep, const Spring& spring, Vec3 position, Vec3 oldVelo, Vec3 velocity, Vec3 normal, double length);
+	float LengthCalculator(Vec3 vector);
+
+	Vec3 calculatePositionTimestepEuler(Vec3 oldPosition, float timestep, Vec3 veloctiy);
+	Vec3 calculateVelocityTimestepEuler(Vec3 oldVelocity, float timestep, Vec3 acceleration);
+	Vec3 calculateAcceleration(Vec3 acceleration, float mass);
+	void Euler(Spring& spring, float timestep);
+
+	void printSpring(const Spring& spring);
+	
 	// Do Not Change
 	void setIntegrator(int integrator) {
 		m_iIntegrator = integrator;