comments

src/MainWindow.cpp

@@ -28,7 +28,7 @@ MainWindow::MainWindow() {
 }
 
 void MainWindow::buildUI() {
-	setMinimumSize(1000, 400);
+	setMinimumSize(1000, 700);
 
 	auto uiLyt = new QVBoxLayout;
 	glWidget = new GLWidget(simulation);
@@ -287,6 +287,9 @@ QWidget * MainWindow::buildAddUI() {
 	addBtn->setToolTip("Add configured pendulum");
 	removeBtn->setToolTip("Remove all pendula");
 
+	addBtn->setStyleSheet("background-color: #aaffaa");
+	removeBtn->setStyleSheet("background-color: #ffaaaa");
+
 	connect(addBtn, &QPushButton::clicked, this, &MainWindow::add);
 	connect(removeBtn, &QPushButton::clicked, this, &MainWindow::remove);
 
@@ -341,6 +344,8 @@ QWidget * MainWindow::buildSimulationUI() {
 	reset->setToolTip("Reset Simulation controls");
 	togglePlay->setToolTip("Pause/Resume Simulation");
 
+	togglePlay->setStyleSheet("background-color: #aaaaff");
+
 	connect(reset, &QPushButton::clicked, this, &MainWindow::resetSimulationControl);
 	connect(togglePlay, &QPushButton::clicked, this, &MainWindow::toggleSimulation);
 	connect(togglePlay, &QPushButton::clicked, [this, togglePlay](){
@@ -403,7 +408,7 @@ void MainWindow::add() {
 					break;
 			}
 			if (rainbow){
-				auto hue = progress + 0.5;
+				auto hue = float(progress + 0.5);
 				c = QColor::fromHsvF(hue, 1, 1);
 			}
 			simulation->pendula.push_back(new Pendulum(M, L, c, angle));

src/MainWindow.h

@@ -17,7 +17,7 @@ private:
 	QWidget * buildSimulationUI();
 	Simulation * simulation;
 
-	GLWidget * glWidget;
+	GLWidget * glWidget = nullptr;
 
 	static const int MaxSegments = 50;
 

src/Pendulum.cpp

@@ -1,6 +1,7 @@
 #include "Pendulum.h"
 #include <iostream>
 #include <QPainter>
+#include <QPainterPath>
 
 Pendulum::Pendulum(const std::vector<double> &M,
 				   const std::vector<double> &L,
@@ -20,25 +21,35 @@ Pendulum::Pendulum(const std::vector<double> &M,
 
 void Pendulum::draw(QPainter *p, double scale) const {
 	p->setPen(color);
-	p->setBrush(Qt::white);
-	Vector previousX(0, 0);
-
-	for (int i = 0; i < X.size(); i++){
-		Vector x = X[i] * scale;
-		p->drawLine(previousX.x, previousX.y, x.x, x.y);
-		previousX = x;
+	p->setBrush(Qt::NoBrush);
+	QPainterPath path;
+	path.moveTo(0, 0);
+	for (auto x : X){
+		x = x * scale;
+		path.lineTo(x.x, x.y);
+	}
+	p->drawPath(path);
 
-		double r = sqrt(M[i] * scale / 5);
-		p->drawEllipse(QPointF(x.x, x.y), r * 2, r * 2);
+	p->setBrush(Qt::white);
+	for (int i = 0; i < M.size(); i++){
+		double r = sqrt(M[i]) * scale / 10;
+		p->drawEllipse(QPointF(X[i].x, X[i].y) * scale, r * 2, r * 2);
 	}
 }
 
 void Pendulum::update(double h, double g) {
-	Vector p1(0, 0);
 
+	// Classic PBD needs multiple loops
+	// Here, I can put all operations safely into one single loop,
+	// because the positions and velocities in X, V are sorted
+	// from the pendulum's origin to it's end which means
+	// that only direct neighbours affect each other
+
+	Vector p1(0, 0);
 	for (int i = 0; i < X.size(); i++){
-		V[i] = V[i] + Vector(0, g * h);
 
+		// explicit integration with gravity as external force
+		V[i] = V[i] + Vector(0, g * h);
 		Vector p2 = X[i] + V[i] * h;
 
 		// solve distance constraint
@@ -56,18 +67,19 @@ void Pendulum::update(double h, double g) {
 		p1 = p1 + deltaP1;
 		p2 = p2 + deltaP2;
 
-		// integrate
+		// update position and velocity
 		if (i > 0){
 			V[i - 1] = (p1 - X[i - 1]) / h;
 			X[i - 1] = p1;
+
+			if (i == X.size() - 1){
+				V[i] = (p2 - X[i]) / h;
+				X[i] = p2;
+			}
 		}
 
 		p1 = p2;
 	}
 
-	// integrate last segment
-	int i = X.size() - 1;
-	V[i] = (p1 - X[i]) / h;
-	X[i] = p1;
 
 }