[JAVA][Beginning Java 8 Games Development]

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Chapter 16 ■ Collision Detection: Creating SVG Polygons for the Game Actors and Writing Code to Detect Collision The SVG Data Format: Hand Coding Vector Shapes There are ten different letters that can be utilized with the numeric (X,Y data point location in 2D space) data in an SVG data string. Each has an upper case (absolute referencing) and a lower case (relative referencing) version. We will be using absolute referencing as we need these data points to match up with pixel locations in the sprite imagery that we are going to “attach” or group these SVG Path data strings with to provide collision detection data guidelines. As you can see in Table 16-1, the SVG data commands provide you a great deal of flexibility in defining custom curves for your <strong>Java</strong> 8 game development. You could even combine all of these scalable vector commands with your <strong>Java</strong> 8 code to create interactive vector (digital illustration) artwork that has never before been experienced, but since this is a game development title, we’re going to use this information to develop highly optimized collision polygons that only use a dozen X,Y data points (somewhere between 12 and 15) to define a relatively detailed collision polygon that will encase our sprite imagery, and provide highly accurate (from the game player’s viewpoint, at least) collision results. Table 16-1. SVG data commands to use for creating SVG path data string (source: Worldwide Web Consortium w3.org) SVG Command Name Symbol Type Parameter Description moveto M Absolute X, Y Defines a Start Of Path at the X,Y using absolute coordinates moveto m Relative X, Y Defines a Start Of Path at the X,Y using relative coordinates closepath Z Absolute None Close SVG Path, by drawing line from last to first coordinate closepath z Relative None Close SVG Path, by drawing line from last to first coordinate lineto L Absolute X, Y Draws a Line from the current point to the next coordinate lineto l Relative X, Y Draws a Line from the current point to the next coordinate horizontal lineto H Absolute X Draws a Horizontal Line from current point to next coordinate horizontal lineto h Relative X Draws a Horizontal Line from current point to next coordinate vertical lineto V Absolute Y Draws a Vertical Line from current point to next coordinate vertical lineto v Relative Y Draws a Vertical Line from current point to next coordinate curveto C Absolute X,Y, X,Y, X,Y Draws a cubic Bezier curve from current point to next point curveto c Relative X,Y, X,Y, X,Y Draws a cubic Bezier curve from current point to next point shortandsmoothcurve S Absolute X,Y, X,Y Draws a cubic Bezier curve from current point to next point (continued) 344 www.it-ebooks.info
Chapter 16 ■ Collision Detection: Creating SVG Polygons for the Game Actors and Writing Code to Detect Collision Table 16-1. (continued) SVG Command Name Symbol Type Parameter Description shortandsmoothcurve s Relative X,Y, X,Y Draws a cubic Bezier curve from current point to next point quadratic Bezier curve Q Absolute X,Y, X,Y Draws a quadratic Bezier curve (current point to next point) quadratic Bezier curve q Relative X,Y, X,Y Draws a quadratic Bezier curve (current point to next point) short quadratic Bezier T Absolute X,Y Draws a short quadratic Bezier (current point to next point) short quadratic Bezier t Relative X,Y Draws a short quadratic Bezier (current point to next point) elliptical arc A Absolute rX, rY, Rot Draws an elliptical arc from current point to next point elliptical arc a Relative rX, rY, Rot Draws an elliptical arc from current point to next point The best way to see how to use the powerful SVG data “path drawing” commands is to get down to learning the work process for creating SVG data-based collision polygon paths. We will learn how to do this using GIMP 2.8.14, using a “quick and dirty” approach, which lets GIMP do 100% of the path creation work. After that, we’ll learn another way to do this by hand using GIMP. A second approach gives you 100% of the path creation control. At the end of this SVG topic, I will also show you how to use another dedicated collision and physics development tool called PhysEd from an innovative game development software tools company, located in Ulm, Germany, called CodeAndWeb GmbH. Creating and Optimizing Collision Data: Using GIMP Fortunately for us, the popular open source digital image editing software package called GIMP, currently at version 2.8.14, has enough Path capabilities, and the ability to export this as SVG datasets, to allow the software to be used as a full-fledged collision polygon creation tool. The GIMP software supports paths using a Path Tool (shown as an old-fashioned fountain pen tip next to a curve data point with Bezier handles coming out of it), which you can see in Figure 16-1 (second icon from the left in the second row of the Toolbox Icons). The reason GIMP supports paths, as it is not generally a vector (path-based) software package, but instead a raster (pixel-based) software package, is because the ability to create a path and then “convert” it to a selection area is a very useful one to the digital image compositing artisan. In fact, we will be using GIMP’s ability to do just the opposite of this: that is, convert an algorithmically created selection set into path data, which will form the foundation of our fully automated, “quick and dirty” SVG Path data creation process. We will take a look at this first, since it is fast, simple, and effective (but “data heavy”). Let’s get started by launching GIMP, and using the File ➤ Open process to open the sprite1.png PNG32 digital image asset that is in your project /src folder. As you can see in Figure 16-1, I have zoomed into the image. This allows me to see the collision data path (initially, this will be a selection) that we’re about to create using the GIMP Toolbox. www.it-ebooks.info 345
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Contents at a Glance About the Auth
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Introduction The Java Programming L
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■ Introduction In Chapter 13 you
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Chapter 1 ■ Setting Up a Java 8 G
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Chapter 2 Setting Up Your Java 8 ID
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Chapter 2 ■ Setting Up Your Java
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Profiling Your Java 8 Game Applicat
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Chapter 3 ■ A Java 8 Primer: An I
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Chapter 4 ■ An Introduction to Ja
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Chapter 5 An Introduction to Game D
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Chapter 6 The Foundation of Game De
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Chapter 8 Creating Your Actor Engin
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Chapter 8 ■ Creating Your Actor E
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Chapter 9 Controlling Your Action F
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Chapter 10 Directing the Cast of Ac
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Chapter 10 ■ Directing the Cast o
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Chapter 11 ■ Moving Your Action F
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Chapter 12 Setting Boundaries for Y
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Chapter 13 ■ Animating Your Actio
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Chapter 17 ■ Enhancing Game Play:
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■ index Background image (cont.)
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■ index InvinciBagel animation (c
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■ index Modifier keywords access
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Beginning Java 8 Games Development
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This Java 8 Game Development book i
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■ Contents NetBeans 8.0 Is User I
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■ Contents ■■Chapter 5: An In
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■ Contents Creating a Hero Superc
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■ Contents Organizing the .update
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■ Contents Optimizing the Scene G
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About the Author Wallace Jackson ha
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Acknowledgments I would like to ack
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