diff --git a/Display.cpp b/Display.cpp
index 3596edb..973329a 100644
--- a/Display.cpp
+++ b/Display.cpp
@@ -1,16 +1,71 @@
 
-// make sure sfml is installed:
-// linux - sudo apt-get install libsfml-dev
-// windows - manual dl from https://www.sfml-dev.org/download.php
-#include <SFML/Graphics.hpp>
 #include <iostream>
+#include <chrono>
+#include <thread>
 
 #include "Display.h"
 #include "Point.h"
+#include "Utility.h"
 
+Display::Display (const std::vector<Point> &pts)
+{
+    if (!m_font.loadFromFile("arial.ttf"))
+    {
+        std::cerr << "font arial.ttf could not be loaded!" << std::endl;
+    }
+
+    m_textStatus.setPosition(OFFSET, HEIGHT - 2*OFFSET);
+    m_textStatus.setFont(m_font);
+    m_textStatus.setString("initializing...");
+    m_textStatus.setCharacterSize(12);
+    m_textStatus.setFillColor(sf::Color::Black);
+
+    size_t points = pts.size();
+    for (size_t i = 0; i < points; ++i)
+    {
+        const Point& pt = pts[i];
+        sf::CircleShape shape(OFFSET);
+        //shape.setPosition(pt.x() - OFFSET, pt.y() - OFFSET); // handle with origin or manually calc position
+        shape.setOrigin(OFFSET, OFFSET);
+        shape.setPosition(pt.x(), pt.y());
+        shape.setFillColor(sf::Color::Green);
+        shape.setOutlineThickness(1.f);
+        shape.setOutlineColor(sf::Color::Black);
+        m_points.push_back(shape);
+        //m_points.append(shape);
+
+        sf::Text label;
+        //label.setPosition(pt.x() - OFFSET / 2, pt.y() - OFFSET / 2 - 3);
+        label.setOrigin(OFFSET / 2 - 1, OFFSET / 2 + 3);
+        label.setPosition(pt.x(), pt.y());
+        label.setFont(m_font);
+        label.setString(std::to_string(i));
+        label.setCharacterSize(12);
+        label.setFillColor(sf::Color::Black);
+        m_labels.push_back(label);
+        //m_points.append(label);
+    }
+}
+
+// multiple options possible:
+// a) draw every frame, using elapsed time for updates
+//      --> not really needed because we have no animations... also uses a lot of performance
+// b) checking every frame if elapsed time since last tick is larger than a specified offset, then draw the field
+//      --> mostly doing nothing but still uses a lot of performance O_o
+// c) just start a simple (c++11 <3) non-busy sleep
+//      --> may delay user input / events but don't care atm :p
 void Display::show()
 {
-    sf::RenderWindow window(sf::VideoMode(WIDTH, HEIGHT), "SFML works!");
+    sf::ContextSettings settings;
+    settings.antialiasingLevel = 8;
+
+    sf::RenderWindow window(sf::VideoMode(WIDTH, HEIGHT), "ALGO Prog2: Quickhull - visualization", sf::Style::Default, settings);
+    /* b)
+    window.setFramerateLimit(0.2);
+
+    sf::Clock clock;
+    sf::Time frameTime = sf::seconds(2); //sf::seconds(1.f / 60.f)
+    sf::Time timeSinceLastUpdate = frameTime; //sf::Time::Zero;*/
     while (window.isOpen())
     {
         sf::Event event;
@@ -20,19 +75,208 @@ void Display::show()
                 window.close();
         }
 
-        window.clear();
-        for (auto &pt : m_points)
+        // a)
+        //update(elapsed);
+        //render(window);
+
+        /* b)
+        timeSinceLastUpdate += clock.restart();
+        // only handle every few seconds because we need no animations
+        if (timeSinceLastUpdate >= frameTime)
         {
-            sf::CircleShape shape(10.f);
-            shape.setPosition(pt.x(), pt.y());
-            shape.setFillColor(sf::Color::Green);
-            window.draw(shape);
-        }
-        window.display();
+            std::cout << "entering update and render" << std::endl;
+
+            // start by getting the most left and right point
+            timeSinceLastUpdate -= frameTime;
+
+            update();
+            render(window);
+        }*/
+
+        // c)
+        // choose a simple sleep
+        update();
+        render(window);
+        std::this_thread::sleep_for(std::chrono::milliseconds(2000));
     }
 }
 
-void Display::setData(std::vector<Point> pts)
+void Display::update ()
 {
-    m_points = pts;
+    // TODO: maybe include Akl–Toussaint heuristic first?
+    // https://en.wikipedia.org/wiki/Convex_hull_algorithms#Akl%E2%80%93Toussaint_heuristic
+
+    unsigned int curStep = (m_step > 5) ? ((m_step - 2) % 4 + 2) : (m_step % 6); // skip init and first step after first run
+
+    std::string text = "(" + std::to_string(m_step) + ") step " + std::to_string(curStep) + ": ";
+    if (curStep == 1)
+    {
+        // first step: select min - max x coordinates
+        m_textStatus.setString(text + "select min - max x coordinates...");
+
+        /* EDIT: manual iteration for combining x and x minmax; also need not previous sorting
+        std::pair<Point, Point> minmax = getMinMaxX(m_points);
+        std::cout << "min: " << minmax.first.x() << ", " << minmax.first.y() <<
+            ", max: " << minmax.second.x() << ", " << minmax.second.y() << std::endl;
+
+        m_hull.setPrimitiveType(sf::Lines);
+        m_hull.append(sf::Vertex(sf::Vector2f(minmax.first.x(), minmax.first.y()), sf::Color::Blue));
+        m_hull.append(sf::Vertex(sf::Vector2f(minmax.second.x(), minmax.second.y()), sf::Color::Blue));*/
+
+        // if use Akl–Toussaint heuristic
+        bool useAkl = false;
+        if (useAkl)
+        {
+            sf::Vector2f topLeft(WIDTH, HEIGHT);
+            sf::Vector2f topRight(0, HEIGHT);
+            sf::Vector2f botLeft(WIDTH, 0);
+            sf::Vector2f botRight(0, 0);
+
+            for (auto& pt : m_points)
+            {
+                sf::Vector2f pos = pt.getPosition();
+                float x = pos.x;
+                float y = pos.y;
+                // TODO: only check explicit x and y seperate!
+                if (x < topLeft.x && y < topLeft.y) topLeft = pos;
+                if (x > topRight.x && y < topLeft.y) topRight = pos;
+                if (x < botLeft.x && y > botLeft.y) botLeft = pos;
+                if (x > botRight.x && y > botRight.y) botRight = pos;
+            }
+
+            /* TODO: use a convex shape? Or build from vertices in render?
+            sf::ConvexShape convex;
+            convex.setPointCount(5);
+            convex.setPoint(0, topLeft);
+            convex.setPoint(0, topRight);
+            convex.setPoint(0, botRight);
+            convex.setPoint(0, botLeft);*/
+
+            //m_hull.setPrimitiveType(sf::Lines);
+            m_hull.setPrimitiveType(sf::LineStrip);
+            m_hull.append(sf::Vertex(topLeft, sf::Color::Blue));
+            m_hull.append(sf::Vertex(topRight, sf::Color::Blue));
+            m_hull.append(sf::Vertex(botRight, sf::Color::Blue));
+            m_hull.append(sf::Vertex(botLeft, sf::Color::Blue));
+            m_hull.append(sf::Vertex(topLeft, sf::Color::Blue));
+        }
+        else
+        {
+            sf::Vector2f left(WIDTH, HEIGHT);
+            sf::Vector2f right(0, 0);
+
+            for (auto& pt : m_points)
+            {
+                sf::Vector2f pos = pt.getPosition();
+                float x = pos.x;
+                float y = pos.y;
+                if (x < left.x) left = pos;
+                if (x > right.x) right = pos;
+            }
+
+            //m_hull.setPrimitiveType(sf::Lines);
+            m_hull.setPrimitiveType(sf::LineStrip);
+            m_hull.append(sf::Vertex(left, sf::Color::Blue));
+            m_hull.append(sf::Vertex(right, sf::Color::Blue));
+        }
+    }
+    else if (curStep == 2)
+    {
+        // second step: split board and find furthest point
+        m_textStatus.setString(text + "split board and find furthest point...");
+
+        for (auto& pt : m_points)
+        {
+            pt.setFillColor(sign(
+                pt.getPosition().x, pt.getPosition().y,
+                m_hull[0].position.x, m_hull[0].position.y,
+                m_hull[1].position.x, m_hull[1].position.y) > 0 ? sf::Color::Red : sf::Color::Green);
+        }
+    }
+    else if (curStep == 3)
+    {
+        // third step: draw triangle, remove inner points
+        m_textStatus.setString(text + "find furthest point and draw triangle...");
+
+        sf::Vector2f pos = m_points[0].getPosition();
+        float maxDistance = 0;
+        for (auto& pt : m_points)
+        {
+            float distance = pDistance(
+                pt.getPosition().x, pt.getPosition().y,
+                m_hull[0].position.x, m_hull[0].position.y,
+                m_hull[1].position.x, m_hull[1].position.y);
+
+            if (pt.getFillColor() == sf::Color::Green)
+            {
+                std::cout << "distance to green point " << pt.getPosition().x << ", " << pt.getPosition().y << ": " << distance << std::endl;
+                    
+            }
+            else if (pt.getFillColor() == sf::Color::Red)
+            {
+                std::cout << "distance to red point " << pt.getPosition().x << ", " << pt.getPosition().y << ": " << distance << std::endl;
+            }
+
+            if (distance > maxDistance)
+            {
+                pos = pt.getPosition();
+                maxDistance = distance;
+            }
+        }
+
+        if (maxDistance > 0)
+        {
+            // TODO: not append but insert between last line points
+            m_hull.append(sf::Vertex(pos, sf::Color::Blue));
+        }
+    }
+    else if (curStep == 4)
+    {
+        // fourth step: remove inner points
+        m_textStatus.setString(text + "remove inner points...");
+    }
+    else if (curStep == 5)
+    {
+        // fifth step: adding new hull point
+
+        // TEMP: TEST check if ends
+        //if (m_step >= 10) m_points.clear();
+
+        if (m_points.size() == 0) m_textStatus.setString(text + "finished calculating convex hull");
+        else m_textStatus.setString(text + "adding new hull point...");
+    }
+    else m_textStatus.setString(text + "invalid status!");
+
+    if (curStep != 5 || m_points.size() > 0) m_step++;
+}
+
+void Display::render (sf::RenderWindow &window)
+{
+    window.clear(sf::Color::White);
+
+    // always print remaining points
+    /*size_t points = m_points.size();
+    for (size_t i = 0; i < points; ++i)
+    {
+        drawPoint(window, i);
+    }*/
+
+    //for (auto& pt : m_points) // points and labels should have the same size -> combine in one loop
+    size_t points = m_points.size();
+    for (size_t i = 0; i < points; ++i)
+    {
+        window.draw(m_points[i]);
+        window.draw(m_labels[i]);
+    }
+
+    // draw already calculated hull
+    //if (step >= 1)
+    {
+        //window.draw(&m_hull[0], m_hull.size(), sf::Lines);
+        window.draw(&m_hull[0], m_hull.getVertexCount(), m_hull.getPrimitiveType());
+    }
+
+    window.draw(m_textStatus);
+
+    window.display();
 }
\ No newline at end of file
diff --git a/Display.h b/Display.h
index 9ab88ca..76b53bd 100644
--- a/Display.h
+++ b/Display.h
@@ -1,17 +1,39 @@
 #pragma once
+#ifndef DISPLAY_H
+
+// make sure sfml is installed:
+// linux - sudo apt-get install libsfml-dev
+// windows - manual dl from https://www.sfml-dev.org/download.php
+#include <SFML/Graphics.hpp>
 
 class Point;
 
+#define OFFSET 10.f
 #define WIDTH 800
 #define HEIGHT 600
 
 class Display
 {
 private:
-    std::vector<Point> m_points;
+    sf::Font m_font;
+    sf::Text m_textStatus;
+
+    //std::vector<Point> m_points;
+    std::vector<sf::CircleShape> m_points;
+    std::vector<sf::Text> m_labels;
+    //sf::VertexArray m_points;
+    //sf::VertexArray m_labels;
+
+    //std::vector<sf::Vertex> m_hull;
+    sf::VertexArray m_hull;
+
+    unsigned int m_step = 0;
+    void update();
+    void render(sf::RenderWindow &);
 
 public:
-    void show();
+    Display(const std::vector<Point> &);
 
-    void setData (std::vector<Point>);
-};
\ No newline at end of file
+    void show();
+};
+#endif // DISPLAY_H
\ No newline at end of file
diff --git a/README.md b/README.md
index 1d99016..98f163f 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,10 @@
 # quickhull
 
+## TODO:
+
+- Point class
+
+    - adding "features" such as "IsInTriangle", ... ?
+
+    - direct member access instead of getters?
+
diff --git a/Utility.h b/Utility.h
new file mode 100644
index 0000000..7d2ec37
--- /dev/null
+++ b/Utility.h
@@ -0,0 +1,91 @@
+#pragma once
+#ifndef UTILITY_H
+
+static float sign(float x, float y, float x1, float y1, float x2, float y2)
+{
+    return (x - x2) * (y1 - y2) - (x1 - x2) * (y - y2);
+}
+
+static float sign (Point &p1, Point &p2, Point &p3)
+{
+    return (p1.x() - p3.x()) * (p2.y() - p3.y()) - (p2.x() - p3.x()) * (p1.y() - p3.y());
+}
+
+static bool IsPointInTriangle(Point &pt, Point &p1, Point &p2, Point &p3)
+{
+    float d1 = sign(pt, p1, p2);
+    float d2 = sign(pt, p2, p3);
+    float d3 = sign(pt, p3, p1);
+
+    bool has_neg = (d1 < 0) || (d2 < 0) || (d3 < 0);
+    bool has_pos = (d1 > 0) || (d2 > 0) || (d3 > 0);
+
+    return !(has_neg && has_pos);
+}
+
+static float pDistance(float x, float y, float x1, float y1, float x2, float y2) {
+
+    float A = x - x1;
+    float B = y - y1;
+    float C = x2 - x1;
+    float D = y2 - y1;
+
+    float dot = A * C + B * D;
+    float len_sq = C * C + D * D;
+    float param = -1;
+    if (len_sq != 0) // in case of 0 length line
+        param = dot / len_sq;
+
+    float xx, yy;
+    if (param < 0) {
+        xx = x1;
+        yy = y1;
+    }
+    else if (param > 1) {
+        xx = x2;
+        yy = y2;
+    }
+    else {
+        xx = x1 + param * C;
+        yy = y1 + param * D;
+    }
+
+    float dx = x - xx;
+    float dy = y - yy;
+    return dx * dx + dy * dy;
+    //return sqrt(dx * dx + dy * dy);
+}
+
+static bool SortForMinXMaxY (const Point& a, const Point& b)
+{
+    if (a.x() != b.x())
+    {
+        return (a.x() < b.x());
+    }
+    return (a.y() > b.y());
+}
+
+static bool SortForMinYMaxX(const Point& a, const Point& b)
+{
+    if (a.y() != b.y())
+    {
+        return (a.x() < b.x());
+    }
+    return (a.y() > b.y());
+}
+
+static void sortPoints (std::vector<Point>& pts)
+{
+    std::sort(pts.begin(), pts.end(), SortForMinXMaxY);
+}
+
+// TODO: what happens if all/more points are on hor/vert line? -> sort for x, than y should handle this
+static std::pair<Point, Point> getMinMaxX(std::vector<Point>& pts)
+{
+    // TODO: check if already sorted? assume array is sorted? call sort utility function???
+    //sortPoints(pts);
+    std::sort(pts.begin(), pts.end(), SortForMinXMaxY);
+
+    return std::make_pair(pts[0], pts[pts.size() - 1]);
+}
+#endif // UTILITY_H
\ No newline at end of file
diff --git a/arial.ttf b/arial.ttf
new file mode 100644
index 0000000..ff0815c
Binary files /dev/null and b/arial.ttf differ
diff --git a/main.cpp b/main.cpp
index a0efeff..f6d3240 100644
--- a/main.cpp
+++ b/main.cpp
@@ -8,6 +8,7 @@
 #include "Display.h"
 #include "Point.h" // TODO: check if there is a usable SFML or c++ class
 #include "Timing.h"
+#include "Utility.h"
 
 // TODOs:
 // - use SFML vec2 instead of Point class
@@ -41,10 +42,32 @@ int main (int argc, char **argv)
         std::cout << "generating random numbers..." << std::endl;
         //srand(static_cast <unsigned> (time(0)));
         srand(static_cast <unsigned> (0)); // fixed seed for testing
+
+        // 2) rectangle
+        //float diff = (2.f * HEIGHT / valCount);
+
+        // 3) circle
+        //float rad = HEIGHT / 2; //8.0f;
+        //float deg = (float)(2 * 3.14159 / valCount);
+
+        float x = 0;
+        float y = 0;
         for (int i = 0; i < valCount; ++i)
         {
-            float x = static_cast <float> (rand()) / (static_cast <float> (RAND_MAX / WIDTH));
-            float y = static_cast <float> (rand()) / (static_cast <float> (RAND_MAX / HEIGHT));
+            // 1) random generation
+            //x = OFFSET + static_cast <float> (rand()) / (static_cast <float> (RAND_MAX / (WIDTH - OFFSET)));
+            //y = OFFSET + static_cast <float> (rand()) / (static_cast <float> (RAND_MAX / (HEIGHT - OFFSET)));
+            x = OFFSET + static_cast <float> (rand()) / (static_cast <float> (RAND_MAX / (WIDTH - 2*OFFSET)));
+            y = OFFSET + static_cast <float> (rand()) / (static_cast <float> (RAND_MAX / (HEIGHT - 2*OFFSET)));
+
+            // 2) rectangle
+            //x = (i%2 == 0) ? OFFSET : WIDTH - OFFSET;
+            //y = diff/2 + (i/2) * diff;
+
+            // 3) position in circle around center, x/y plane
+            //x = WIDTH/2 + rad * cosf(i * deg);
+            //y = HEIGHT/2 + rad * sinf(i * deg);
+
             points.push_back(Point(x, y));
         }
     }
@@ -76,7 +99,8 @@ int main (int argc, char **argv)
         }
     }
 
-    // TODO: need sort here?
+    // TODO: sort here, once and for all? xD
+    //sortPoints(points);
     for (Point& pt : points)
     {
         std::cout << "pt: " << pt.x() << ", " << pt.y() << std::endl;
@@ -84,9 +108,10 @@ int main (int argc, char **argv)
 
     if (vis)
     {
-        // TODO: use data as ctor argument? pointer?
-        Display display;
-        display.setData(points);
+        // TEST to check SFML coordinate system
+        //points.push_back(Point(0, 0));
+
+        Display display(points);
         display.show();
     }