Drawing simple shapes

Introduction

This new tutorial will teach you how to draw simple 2D shapes, such as lines, rectangles, circles or polygons with SFML.

Building custom shapes

To build a custom shape with SFML, you have to use the sf::Shape class.
A shape is basically a convex polygon, in which each point can have its own position and color. You can also add an automatic outline to a shape, each point having the ability to define its own color for the outline.
It is important to define the points of a shape in order (clockwise or counter-clockwise), otherwise the shape may be ill-formed. It is also important to keep the shape convex, otherwise it won't be rendered properly. It you want to draw concave shapes, try to split them into several convex sub-shapes.

To add a new point to a shape, use the AddPoint function :

sf::Shape Polygon;
Polygon.AddPoint(0, -50,  sf::Color(255, 0, 0),     sf::Color(0, 128, 128));
Polygon.AddPoint(50, 0,   sf::Color(255, 85, 85),   sf::Color(0, 128, 128));
Polygon.AddPoint(50, 50,  sf::Color(255, 170, 170), sf::Color(0, 128, 128));
Polygon.AddPoint(0, 100,  sf::Color(255, 255, 255), sf::Color(0, 128, 128));
Polygon.AddPoint(-50, 50, sf::Color(255, 170, 170), sf::Color(0, 128, 128));
Polygon.AddPoint(-50, 0,  sf::Color(255, 85, 85),   sf::Color(0, 128, 128));

The parameters are the X and Y coordinates of the point, its color, and an optional color for outline. Note that you can also pass a sf::Vector2f instead of two floats for the position of the point.

Once added to the shape, the points' attributes (position, color and outline) can be read or written individually with these accessors :

// Get the attributes of the third point
sf::Vector2f Position     = Polygon.GetPointPosition(2);
sf::Color    Color        = Polygon.GetPointColor(2);
sf::Color    OutlineColor = Polygon.GetPointOutlineColor(2);

// Set the attributes of the second point
Polygon.SetPointPosition(1, sf::Vector2f(50, 100));
Polygon.SetPointColor(1, sf::Color::Black);
Polygon.SetPointOutlineColor(1, sf::Color(0, 128, 128));

To control the outline width of the whole shape, use the SetOutlineWidth function :

// Set an outline width of 10
Polygon.SetOutlineWidth(10);

Ok nice, we now have a shape with an outline. But what if we just want to draw its outline without filling it ? Or remove this outline ? There are two functions to enable or disable filling and drawing the outline :

// Disable filling the shape
Polygon.EnableFill(false);

// Enable drawing its outline
Polygon.EnableOutline(true);

Like every drawable object in SFML, shape objects inherit the common functions to set their position, rotation, scale, color and blending mode.

Polygon.SetColor(sf::Color(255, 255, 255, 200));
Polygon.Move(300, 300);
Polygon.Scale(3, 2);
Polygon.Rotate(45);

Finally, drawing a shape is also like any other drawable object in SFML :

App.Draw(Polygon);

Predefined shapes

SFML provides helper static functions to create simple shapes such as lines, rectangles and circles :

sf::Shape Line   = sf::Shape::Line(X1, Y1, X2, Y2, Thickness, Color, [Outline], [OutlineColor]);
sf::Shape Circle = sf::Shape::Circle(X, Y, Radius, Color, [Outline], [OutlineColor]);
sf::Shape Rect   = sf::Shape::Rectangle(X1, Y1, X2, Y2, Color, [Outline], [OutlineColor]);

The values for outline width and color are optional ; it's disabled by default.

Conclusion

With this new class you'll now be able to draw simple rectangles, circles, or custom polygons without having to use an image and a sprite. Let's now have a look at something a bit more exciting : views.