Drawing 2D geometric primitives

In this recipe, we will learn how to draw the following 2D geometric shapes, as filled and stroked shapes:

• Circle

• Ellipse

• Line

• Rectangle

Getting ready

Include the necessary header to draw in OpenGL using Cinder commands.

Add the following line of code at the top of your source file:

#include "cinder/gl/gl.h"

How to do it…

We will create several geometric primitives using Cinder's methods for drawing in 2D. Perform the following steps to do so:

1. Let's begin by declaring member variables to keep information about the shapes we will be drawing.

   Create two ci::Vec2f objects to store the beginning and end of a line, a ci::Rectf object to draw a rectangle, a ci::Vec2f object to define the center of the circle, and a float object to define its radius. Finally, we will create aci::Vec2f to define the ellipse's radius and two float objects to define its width and height.

   Let's also declare two ci::Color objects to define the stroke and fill colors.

   Vec2f mLineBegin,mLineEnd;
   Rect...