[JAVA][Beginning Java 8 Games Development]

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Chapter 5 ■ An Introduction to Game Design: Concepts, Multimedia, and Using Scene Builder Also, note that you can set the percentage of dithering that is used. I often select either the 0 percent or 100 percent setting; however, you can fine-tune the dithering effect anywhere between these two extreme values. You can also choose between dithering algorithms, because, as you probably have surmised, the dithering effect is created using dithering algorithms, which are part of the indexed file format (in this case, PNG8) compression routines. I use diffusion dithering, which gives a smooth effect along irregularly shaped gradients, as is seen in the car fender. You can also use a noise option, which is more randomized, or a pattern option, which is less so. The diffusion option usually gives the best results, which is why I choose it when I am using indexed color (which is not often). Dithering, as you might imagine, adds data patterns to an image that are more difficult to compress. This is because smooth areas in an image, such as gradients, are easier for the compression algorithm to compress than sharp transitions (edges) or random pixel patterns (e.g., dithering or “noise” from a camera CCD). Therefore, applying the dithering option will always increase the data footprint by a few percentage points. Be sure to check the resulting file size with and without dithering applied (selected in the Export dialog) to see if it is worth the improved visual result that it affords. Note that there is also a transparency option (check box) for indexed color PNG images but that the alpha channel used in PNG8 images is only 1 bit (on/off), not 8 bit, as with PNG32. You can also increase the data footprint of your image by adding an alpha channel to define transparency for compositing. This is because by adding an alpha channel you will be adding in another 8-bit color channel (or a transparency channel, actually) to the image being compressed. If you need an alpha channel to define transparency for your image to support future compositing requirements, such as using the image as a game sprite, there is not much choice but to include the alpha channel data. If your alpha channel contains all zeroes (or uses an all-black fill color), which would define your imagery as being completely transparent, or contains all FF values (or uses an all-white fill color), which would define your image as being completely opaque, you would essentially (in practical terms) be defining an alpha that does not contain any useful alpha data values. The transparent image would therefore need to be removed, and the opaque image would need to be defined as a PNG24 rather than a PNG32. Finally, most alpha channels that are used to mask objects in the RGB layers of the digital image should compress very well. This is because the alpha channel is primarily areas of white (opaque) and black (transparent), with some medium-gray values along the edge between the two colors to antialias the mask (see Figure 5-2). These gray areas contain the antialiasing values in the alpha channel, and will provide the visually smooth-edge transitions between the object in the RGB layers of the image and any background color or background images that may be used behind it. The reason for this is that in the alpha channel image mask, an 8-bit transparency gradient (from white to black) defines levels of transparency, which could be thought of as per-pixel blending (opacity) strength. Therefore, the medium-gray values on the edges of each object in the mask (which is contained in the alpha channel) will serve essentially to average the colors of the object edge, and any target background, no matter what color (or image) value it may contain. This offers real-time antialiasing with any target background that may be used, including animated backgrounds. Digital Video and Animation: Frames, Rate, Looping, Direction Interestingly, all the concepts that I have just covered for digital images apply equally well to digital video and animation, as both formats use digital images as the foundation for their content. Digital video and animation extend digital imaging into the fourth dimension (time) by using frames. The two formats are composed of an ordered sequence of frames, which are displayed rapidly over time. The term “frame” comes from the film industry, in which, even today, frames of film are run through film projectors at a rate of 24 frames per second (24FPS), which creates the illusion of motion. Because both digital video and animation are made up of a collection of frames containing digital images, the concept of frame rate, expressed as frames per second, is also very important when it comes to the memory data footprint optimization work process (for animation assets) as well as the digital video file size data footprint optimization work process. As discussed previously, in JavaFX this attribute for animation is stored in the Animation object rate variable (see Chapter 4). www.it-ebooks.info 113
Chapter 5 ■ An Introduction to Game Design: Concepts, Multimedia, and Using Scene Builder The optimization concept regarding frames in an Animation object or digital video asset is very similar to the optimization concept regarding pixels in an image (the resolution of a digital image): the fewer used, the better! This is because the number of frames in an animation or video multiplies both the system memory used and the filesize data footprint with each frame. In digital video, not only does each frame’s (image) resolution, but also the frame rate (specified in the Compression Settings dialog) impact file size. Earlier in this chapter, you learned that if you multiply the number of pixels in the image by its number of color channels, you will get the raw data footprint for the image. With animation and digital video, you will now multiply that number again by the number of frames that need to be used to create the illusion of motion. Therefore, if you have an animated VGA (RGB) background plate for your game (remember that each frame is 900KB) that uses five frames to create the illusion of motion, you are using 900KB × 5, or 4,500KB (4.5MB), of system memory to hold that animation. Of course, this is too much memory to use for a background, which is why you will be using static backgrounds with sprite overlays to achieve this exact same end result in less than a megabyte. The calculation for digital video is a bit different, as it has hundreds or thousands of frames. For digital video you would multiply your raw image data size by the number of frames per second (frame rate) at which the digital video is set to play back (this frame rate value is specified during the compression process), and then multiply that result by the total number of seconds of content duration contained in your video file. To continue with the VGA example, you know that a 24-bit VGA image is 900KB. This makes the calculation to take this to the next level easy. Digital video traditionally runs at 30FPS, so 1 second of standard definition raw (uncompressed) digital video would be 30 image frames, each of which is 900KB, yielding a total data footprint of 27,000KB! You can see why having video compression file formats such as MPEG-4 H.264 AVC, which can compress the massive raw data footprint that digital video can create, is extremely important. The JavaFX media package uses one of the most impressive video compression codecs (“codec” stands for code-decode) which is also supported in HTML5 and Android, the aforementioned MPEG-4 H.264 AVC (advanced video codec). This is quite convenient for developer asset optimization, as one single digital video asset can be used across JavaFX, HTML5, and Android applications. Just in case you want to use digital video in the background of your game (which I do not recommend), I am going to cover the basics of digital video compression and optimization next. Digital Video Compression Concepts: Bit Rate, Data Streaming, SD, HD, UHD Let’s begin with the primary or standard resolutions that are used in commercial video. These also happen to be common device screen resolutions, probably because if the screen pixel resolution matches the video pixel resolution that is being played full screen on a screen, there will be zero scaling, which can cause scaling artifacts. Before high definition came along, video was standard definition (SD) and used a vertical resolution of 480 pixels. VGA is an SD resolution, and 720 × 480 could be called wide SD resolution. High definition (HD) video comes in two resolutions, 1,280 × 720, which I call pseudo HD, and 1,920 × 1,080, which the industry calls true HD. Both HD resolutions feature a 16:9 aspect ratio and are used in TVs and iTVs, smartphones, tablets, e-book readers, and game consoles. There is also an ultra high definition (UHD) resolution out now that features 4,096 × 2,160 pixels. Video streaming is a more complicated concept than resolution, as it involves playing back video data over a wide expanse, such as the one between your Java 8 game application and the remote video data server that will hold your potentially massive digital video assets. Furthermore, the device that your Java game application is running on will be communicating in real time with remote data servers, receiving video data packets as the video plays (it is termed streaming because the video is streaming from the video server, over the Internet, and into the hardware device). Video streaming is supported by the MPEG-4 H.264 AVC format codec (encoder-decoder pair). The last concept that you need to understand is bit rate. Bit rate is the key setting used in the video compression process, as bit rates represent your target bandwidth, or the data pipe size that is able to accommodate a certain number of bits streaming through it every second. The bit-rate setting should also take into consideration the CPU processing power that exists within any given Java-capable device, making your digital video’s data optimization even more challenging. Fortunately, most devices these days feature dualcore or quadcore CPUs! 114 www.it-ebooks.info
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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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Profiling Your Java 8 Game Applicat
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Chapter 3 ■ A Java 8 Primer: An I
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Chapter 8 Creating Your Actor Engin
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Chapter 12 Setting Boundaries for Y
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Chapter 14 ■ Setting Up the Game
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Chapter 15 Implementing Game Audio
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Chapter 17 Enhancing Game Play: Cre
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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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