[JAVA][Beginning Java 8 Games Development]

Chapter 8 ■ Creating Your Actor Engine: Design the Characters for Your Game and Define Their Capabilities
The InvinciBagel Sprite Images: Visual Action States
Besides designing the optimal Actor Engine classes to use to implement characters, treasure, and obstacles in a game,
the other important thing to optimize is the main character for the game, and the different states of animation that
a character will move between, based on the movement of the character by the player. From a memory optimization
standpoint, the fewer image frames that we can accomplish all of this in, the better. As you can see in Figure 8-2, I will
provide all of the InvinciBagel character motion states using only nine different sprite image assets; some of these can
be used in more than one way: for instance, by using the pX and pY variables, which will allow us to rotate these sprite
frames around any pivot point that we choose. An example of this is center pivot point placement for the FLY state,
seen in the middle of Figure 8-2, which gives us a take-off (fly up), flying, and landing (fly down) simply by rotating this
image 50 degrees clockwise (to a horizontal orientation) to 100 degrees clockwise (tilting to fly down, instead of up).
Figure 8-2. The nine primary character motion sprites for the InvinciBagel character that will be used during the game
Even though we are providing offset and pivot point capabilities in our sprite Actor Engine abstract classes, that
doesn’t mean that we should not make sure that our motion sprite image states are well synchronized with each
other. This is so that we do not routinely have to use these pivot or offset capabilities to get good visual results. This is
what I term sprite registration, and involves positioning the different sprite states optimally relative to each other.
Some examples of sprite registration between sprite frames that will be used with each other can be seen in
Figure 8-3. For instance, the starting to run imageStates[1] sprite should start its run cycle with the same foot position
as a standing (or waiting) imageStates[0] sprite, as seen on the left side of Figure 8-3. Also, the running imageStates[2]
sprite should keep its body portion as still as possible, relative to the imageStates[1] starting to run sprite. A preparing
to land imageStates[6] sprite should change foot positioning realistically relative to the landed imageStates[7] sprite.
Figure 8-3. Sprite registration (alignment) to make sure the transition motion is smooth
What you want to do to optimize sprite registration, relative to all of the other sprites, is to put all of your digital
image sprites into the same square 1:1 aspect ratio resolution image format, and place them all in layers in a digital
image compositing software package, such as GIMP or Photoshop. Then use the move tool and nudge (single pixel
movements using arrow keys on keyboard) each sprite into position, relative to whichever two layers you have
visibility (toggled on/off using the eye icon on the left of each layer) turned on for. The result is shown in Figure 8-3.
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