Book Image

Game Programming Using Qt: Beginner's Guide

By : Lorenz Haas, Witold Wysota, Witold Wysota, Lorenz Haas
Book Image

Game Programming Using Qt: Beginner's Guide

By: Lorenz Haas, Witold Wysota, Witold Wysota, Lorenz Haas

Overview of this book

Qt is the leading cross-platform toolkit for all significant desktop, mobile, and embedded platforms and is becoming more popular by the day, especially on mobile and embedded devices. Despite its simplicity, it's a powerful tool that perfectly fits game developers’ needs. Using Qt and Qt Quick, it is easy to build fun games or shiny user interfaces. You only need to create your game once and deploy it on all major platforms like iOS, Android, and WinRT without changing a single source file. The book begins with a brief introduction to creating an application and preparing a working environment for both desktop and mobile platforms. It then dives deeper into the basics of creating graphical interfaces and Qt core concepts of data processing and display before you try creating a game. As you progress through the chapters, you’ll learn to enrich your games by implementing network connectivity and employing scripting. We then delve into Qt Quick, OpenGL, and various other tools to add game logic, design animation, add game physics, and build astonishing UI for the games. Towards the final chapters, you’ll learn to exploit mobile device features such as accelerators and sensors to build engaging user experiences. If you are planning to learn about Qt and its associated toolsets to build apps and games, this book is a must have.
Table of Contents (18 chapters)
Game Programming Using Qt
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Time for action – creating items with different origins


Let's have a closer look at these three items defined by the following code snippet:

QGraphicsRectItem *itemA = QGraphicsRectItem(-10, -10, 20, 20);
QGraphicsRectItem *itemB = QGraphicsRectItem(0, 0, 20, 20);
QGraphicsRectItem *itemC = QGraphicsRectItem(10, 10, 20, 20);

What just happened?

All three items are rectangles with a side length of 20 pixels. The difference between them is the position of their coordinate origin points. itemA has its origin in the center of the rectangle, itemB has its origin in the top-left corner of the rectangle, and itemC has its origin outside the drawn rectangle. In the following diagram, you see the origin points marked as red dots.

So what's the deal with these origin points? On the one hand, the origin point is used to create a relation between the item's coordinate system and the scene's coordinate system. As you will see later in more detail, if you set the position of the item on the scene, the position...