game-physics/Simulations/MassSpringSystemSimulator.cpp

#include "MassSpringSystemSimulator.h"

MassSpringSystemSimulator::MassSpringSystemSimulator()
{
	m_iTestCase = 0;
	m_fMass = 10;
	m_fStiffness = 40;
	int m_iIntegrater = 0;

	auto first = addMassPoint(Vec3(0, 0, 0), Vec3(-1, 0, 0), true);
	auto second = addMassPoint(Vec3(0, 2, 0), Vec3(1, 0, 0), true);
	addSpring(first, second, 1.0);
	m_fStiffness = 40;
}

const char* MassSpringSystemSimulator::getTestCasesStr()
{
	return "Demo1,Demo2,Demo3,Demo4";
}

void MassSpringSystemSimulator::initUI(DrawingUtilitiesClass* DUC)
{
	this->DUC = DUC;
	switch (m_iTestCase)
	{
	case 0:break;
	case 1:
	
		break;
	case 2:
		break;
	default:break;
	}
}

void MassSpringSystemSimulator::reset()
{
	m_mouse.x = m_mouse.y = 0;
	m_trackmouse.x = m_trackmouse.y = 0;
	m_oldtrackmouse.x = m_oldtrackmouse.y = 0;
}



void MassSpringSystemSimulator::drawFrame(ID3D11DeviceContext* pd3dImmediateContext)
{
	
	for (size_t i = 0; i < springs.size(); i++) {
		auto sp = springs.at(i);
		if (!sp.isValid())
		{
			springs.erase(springs.begin() + i);
			continue;
		}
		auto mp1 = sp.mp1.lock();
		auto mp2 = sp.mp2.lock();
		DUC->setUpLighting(Vec3(), 0.4 * Vec3(1, 1, 1), 100, 0.6 * Vec3(0.97, 0.86, 1));
		
		DUC->drawSphere(mp1->position, Vec3(0.01));
		DUC->drawSphere(mp2->position, Vec3(0.01));

		DUC->beginLine();
		DUC->drawLine(mp1->position, Vec3(1,0,0), mp2->position, Vec3(0,1,0));
		DUC->endLine();
	}
}

void MassSpringSystemSimulator::notifyCaseChanged(int testCase)
{
	m_iTestCase = testCase;
	switch (m_iTestCase)
	{
	case 0:
		cout << "Demo1 !\n";

//simulateTimestep(1);

		break;
	case 1:
		cout << "Demo2 \n";
		//m_iNumSpheres = 100;
		//m_fSphereSize = 0.05f;
		break;
	case 2:
		cout << "Demo3 !\n";
		break;
	case 3:
		cout << "Demo 4 !\n";
	default:
		//cout << "Demo4 !\n";
		break;
	}
}

void MassSpringSystemSimulator::externalForcesCalculations(float timeElapsed) 
{
	Point2D mouseDiff;
	mouseDiff.x = m_trackmouse.x - m_oldtrackmouse.x;
	mouseDiff.y = m_trackmouse.y - m_oldtrackmouse.y;
	if (mouseDiff.x != 0 || mouseDiff.y != 0)
	{
		Mat4 worldViewInv = Mat4(DUC->g_camera.GetWorldMatrix() * DUC->g_camera.GetViewMatrix());
		worldViewInv = worldViewInv.inverse();
		Vec3 inputView = Vec3((float)mouseDiff.x, (float)-mouseDiff.y, 0);
		Vec3 inputWorld = worldViewInv.transformVectorNormal(inputView);
		// find a proper scale!
		float inputScale = 0.001f;
		inputWorld = inputWorld * inputScale;
		
		//m_vfMovableObjectPos = m_vfMovableObjectFinalPos + inputWorld;
	}
	else {
		//m_vfMovableObjectFinalPos = m_vfMovableObjectPos;
	}

}



void MassSpringSystemSimulator::simulateTimestep(float timeStep)
{
	//update current setup for each frame
	switch (m_iTestCase) {
	case 0:
		//update the masspoint
		cout << "Euler \n";
		
		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;
	}

	Euler(0, 1, 0, timeStep);
}

void MassSpringSystemSimulator::onClick(int x, int y)
{
	m_trackmouse.x = x;
	m_trackmouse.y = y;
}

void MassSpringSystemSimulator::onMouse(int x, int y)
{
	m_oldtrackmouse.x = x;
	m_oldtrackmouse.y = y;
	m_trackmouse.x = x;
	m_trackmouse.y = y;
}

void MassSpringSystemSimulator::setMass(float mass)
{
	m_fMass = mass;
}

void MassSpringSystemSimulator::setStiffness(float stiffness)
{
	m_fStiffness = stiffness;
}

void MassSpringSystemSimulator::setDampingFactor(float damping)
{
	m_fDamping = damping;
}

int MassSpringSystemSimulator::addMassPoint(Vec3 position, Vec3 Velocity, bool isFixed)
{
	MassPoint masspoint;
	masspoint.position = position;
	masspoint.velocity = Velocity;
	masspoint.isFixed = isFixed;
	masspoints.push_back(std::make_shared<MassPoint>(masspoint));

	return masspoints.size() - 1;
}

void MassSpringSystemSimulator::addSpring(int masspoint1, int masspoint2, float initialLength)
{
	auto mp1 = masspoints.at(masspoint1);
	auto mp2 = masspoints.at(masspoint2);

	Spring spring;
	spring.mp1 = mp1;
	spring.mp2 = mp2;
	spring.initialLength = initialLength;

	springs.push_back(spring);
}

int MassSpringSystemSimulator::getNumberOfMassPoints()
{
	return masspoints.size();
}

int MassSpringSystemSimulator::getNumberOfSprings()
{
	return springs.size();
}

Vec3 MassSpringSystemSimulator::getPositionOfMassPoint(int index)
{
	auto mp = masspoints.at(index);
	return mp->position;
}

Vec3 MassSpringSystemSimulator::getVelocityOfMassPoint(int index)
{
	auto mp = masspoints.at(index);
	return mp->velocity;
}

void MassSpringSystemSimulator::applyExternalForce(Vec3 force)
{

}

Vec3 MassSpringSystemSimulator::calcualtePositionTimestepEuler(Vec3 oldPosition, float timestep, Vec3 velocity)
{
	return oldPosition + timestep * velocity;
}

Vec3 MassSpringSystemSimulator::calcualteVelocityTimestepEuler(Vec3 oldVelocity, float timestep, Vec3 acceleration)
{
	return oldVelocity + acceleration * timestep;
}

Vec3 MassSpringSystemSimulator::calculateAcceleration(Vec3 force, float mass)
{
	return force / mass;
}

void MassSpringSystemSimulator::Euler(int index1, int index2, int indexSpring, float timestep)
{
	//take old position and send to calculatePositionTimestepEuler
	auto mp = masspoints.at(index1);
	auto mp2 = masspoints.at(index2);
	Vec3 PosVector = mp->position - mp2->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 - springs.at(0).initialLength) * normalized;
	auto foreP2 = -1 * force;
	auto veloc = calcualteVelocityTimestepEuler(mp->velocity, timestep, calculateAcceleration(force, 10.));
	auto pos = calcualtePositionTimestepEuler(mp->position, timestep, veloc);

	auto veloc2 = calcualteVelocityTimestepEuler(mp2->velocity, timestep, calculateAcceleration(foreP2, 10.));
	auto pos2 = calcualtePositionTimestepEuler(mp2->position, timestep, veloc2);

	// Update Positions and Velocity
	mp->position = pos;
	mp->velocity = veloc;
	mp2->position = pos2;
	mp2->velocity = veloc2;
}