OpenGL in Jitter
What is OpenGL ?
OpenGL is an application programming interface---‘‘API’’ for short---which is merely a software library for accessing features in graphics hardware. It is designed as a streamlined, hardware-independent interface that can be implemented on many different types of graphics hardware systems, or entirely in software (if no graphics hardware is present in the system) independent of a computer’s operating or windowing system.
OpenGL is implemented as a client-server system, with the application you write being considered the client, and the OpenGL implementation provided by the manufacturer of your computer graphics hardware being the server. In practical terms it means that all that you draw using OpenGL will require resources from your GPU (Graphic Processor Unit, or graphic card), and this is why 3D animators and PC video gamers will prefer a powerful GPU over a powerful CPU. Indeed, most animation programs use OpenGL and it is also used for video games. Video graphic cards in most computers support it in hardware, so openGL scenes can be rendered with an acceptable speed.
NVIDIA GTX Titan. One of the most powerful GPU units now days
Alienware computers, are used by gamers and often by 3D animators , these machines are equipped with powerful GPU units like NVIDIA GTX 1080
The OpenGL Coordinate System in Jitter
Because OpenGL deals with 3D graphics, it uses a three-dimensional coordinate system along the x-, y-, and z-axis. This coordinate system is easy to understand because our world has the same three dimensions: width, height, and depth. In any coordinate system, the direction of each axis is important. Generally, in OpenGL, when you face the computer screen, the horizontal direction is the x-axis (right direction is positive), the vertical direction is the y-axis (up direction is positive), and the direction from the screen to the viewer is the z-axis (the left side of figure below). The viewer’s eye is located at the origin (0.0, 0.0, 0.0), and the line of sight travels along the negative direction of the z-axis, or from you into the screen (see the right side of the figure below).In Jitter, the boundaries of the Context Window ( let's say for now : our screen), are in a range from -1 to 1, where 0 is at the center.
The OpenGL coordinate system in Jitter, the boundaries of the Context window are in a range from -1 to 1, where 0 is at the center.
The OpenGL coordinate system and the computer screen
The OpenGL coordinate system and the computer screen and user.