[PLUGIN] BulletML

<?xml version="1.0" ?>
<!DOCTYPE bulletml SYSTEM "http://www.asahi-net.or.jp/~cs8k-cyu/bulletml/bulletml.dtd">
<bulletml xmlns="http://www.asahi-net.or.jp/~cs8k-cyu/bulletml">
    <action label="top">
        <fire>
            <bullet>
                <direction type="absolute">90</direction>
            </bullet>
        </fire>
    </action>
</bulletml>
[/code:1z4lqy6h]

This script fires one bullet at angle 90, default speed. Not terribly useful yet. Here's a more complex example:

[code:1z4lqy6h]
<?xml version="1.0" ?>
<!DOCTYPE bulletml SYSTEM "http://www.asahi-net.or.jp/~cs8k-cyu/bulletml/bulletml.dtd">
<bulletml xmlns="http://www.asahi-net.or.jp/~cs8k-cyu/bulletml">
    <action label="top">
        <fire>
            <direction type="aim">0</direction>
            <speed>150</speed>
            <bulletRef label="seed" />
        </fire>
    </action>

    <bullet label="seed">
        <action>
            <repeat>
                <times>100</times>
                <action>
                    <fire>
                        <direction type="absolute">$rand * 360</direction>
                        <speed>200 + $rank * 200</speed>
                        <bullet />
                    </fire>
                </action>
                <wait>50</wait>
            </repeat>
        </action>
    </bullet>
</bulletml>
[/code:1z4lqy6h]

This script fires a slow-moving bullet that in turn spawns 100 other bullets at 50ms intervals, in random directions. The speed of these bullets depends on the difficulty level (rank).

Check the demo game for a variety of patterns.

[b]* About this plugin[/b]

This plugins adds a BulletML object that can read and play BulletML files. It is a bit like the existing particle system object; you can have multiple emitters and each object manages its own bullets.

While any bullet pattern could be created with events, describing them with external files is more reusable and they can be modified without changing the .cap, including after the game is published.

[b]* Appearance[/b]

You can either let the emitter render the bullets (just like a particle system) by setting a texture or you can replace the bullets with Sprite objects.

[b]* Collisions[/b]

If you are not using Sprites as bullets this object has its own collision condition. All collisions are bullet point against object bounding box. Arcade shoot 'em up games usually use hidden hitboxes that are smaller than the player craft.

Bullets are destroyed when they collide with an object.

[b]* Lifetime[/b]

Bullets are destroyed when they collide, exit the screen (toggleable), their associated Sprite is destroyed or a set number of milliseconds is exceeded.

If you Destroy the emitter, all its associated bullets vanish. This is a technical limitation, but not too tricky to work around.

[b]* Units[/b]

Speeds are pixels per second, time units are milliseconds. The BML spec treats time values as frames for some reason but this wouldn't be very useful when frame rate can be anything from tens to hundreds.

Separate multiplier values are provided for speeds and time values.

[b]* Directions, targeting[/b]

(absolute directions) When script type is "vertical" 0 is right and 90 down. With "horizontal" 0 is up and 90 right.

If you want the bullets to fly in the direction the emitter is pointing, use "relative" direction and angle 0.

When no direction is specified, BulletML spec assumes "aim" is assumed; bullet flies to the x,y coordinate set by "Set target position" action.

[b]* Learning BulletML[/b]

Reading just the reference is not very good for learning the capabilities of this system. Check out the demo game, this [url=http://www.asahi-net.or.jp/~cs8k-cyu/bulletml/bulletml_applet_e.html]Java-based demo applet[/url] or download some of Kenta Cho's games - many of them contain BulletML files you can take apart.