[JAVA][Beginning Java 8 Games Development]

Chapter 16 ■ Collision Detection: Creating SVG Polygons for the Game Actors and Writing Code to Detect Collision
After you update your iBagel Bagel() constructor method, with accurate SVG data for your collision polygon,
update the iP0 fixed Actor props, using the coordinates for the four corner pixels, to create a square collision polygon,
as can be seen in Figure 16-25. The upper-left origin corner for any image is going to be 0,0, so the first SVG command
is going to be M0,0, or “moveto origin.” Next, we want to draw a “lineto” using the L command, the lower-left corner,
which would use the L0,32 command and data set, since this brick image is 32 pixels tall (Y), and 72 pixels wide (X).
The next data pair will not need to be prefaced by an L command, since any implementation of an SVG data
parsing algorithm will assume the command used for the previous data pair, if none has been explicitly specified. Your
lower-right corner of the brick image will use X,Y coordinate 72,32. The upper-right corner of this image would use X,Y
coordinate 72,0. The Z command can be used to connect the upper-right corner of this prop image with the origin, so
that we have collision detection on the top of the brick, in this particular use-case, using a closed polygon. As you can
see in Figure 16-25, you can either use commas or spaces with SVG data, so both of these method calls should work:
iPR0 = new Prop("M0 0 L0 32 72 32 72 0 Z", 0, 148, iP0);
iPR0 = new Prop("M0,0 L0,32 72,32 72,0 Z", 0, 148, iP0);
OR:
The second example uses the same amount of space in NetBeans 8, and shows the data point pairs better. I am
going to comment out all the code related to the iP1 Actor Prop object, as you can see in Figures 16-25 and 16-26, so
that these larger Prop Actor objects are “disabled” for now, and do not appear on the Stage (and in the Scene), and will
not interfere with our basic code development for implementing collision detection.
Now we are ready to use the Run ➤ Project work process, and make sure that the InvinciBagel character, as well
as the four golden bricks that we are going to use for testing the collision detection code are in place and that the large
mossy rock objects are no longer anywhere to be seen on the Stage. As you can see in Figure 16-27, we have the Scene
set up for developing the basic collision detection code, and we can now focus on putting this Java 8 game code into
place, before we start to work on implementing further Scene designs, game play design, game play logic, physics and
scoring engine code, all of which we will be implementing in the next chapter 17.
Figure 16-27. Use the Run ➤ Project work process and test the game
368
www.it-ebooks.info