Flint Particle System Forum - Single Image Particles at Specific Locations

Single Image Particles at Specific Locations

ericr — Thu, 08 May 2008 23:12:33 +0100

So consider the game Super Mario Bros. Lets say Mario violently takes down a row of five enemies of differing types [minding their own business, of course] with fireballs. Let's say they should all fly off in different directions when they get hit, starting at their current location.

Let's say that when they're hit, some crazy "functionality" converts them into Flint Particles. How would, given a single Renderer object (spanning the play space, of course), one set up each Particle in the correct location with an Emitter? Is this currently possible? Would this need to be implemented possibly as a new Initializer?

Further, if the Emitter is already running, is there a way to dynamically instruct it to generate new particles?

Single Image Particles at Specific Locations

Richard — Sat, 10 May 2008 15:00:06 +0100

Look at the addDisplayObjects method in the Emitter, this will do what I think you want.

Single Image Particles at Specific Locations

ericr — Wed, 14 May 2008 22:19:07 +0100

Potential bug in Emitter::addDisplayObject():

I would wrap line 466 in an if-block. If someone never added the DisplayObject "obj" to the Display List then that will result in a null pointer exception. If they didn't add it the point would default to (0,0) which, to me, is fine.

Perhaps something like:

if(obj.parent)
{
	obj.parent.removeChild( obj );	// Line 466.
}

Thoughts?

Other than that, the function looks to do exactly what I need :}

Single Image Particles at Specific Locations

ericr — Thu, 15 May 2008 16:47:25 +0100

Beyond the bug I mention above, it's not exactly what I need. It's close, though. I will modify the function until I get what I need and I'll post it here.

The problem for me in that function is that you reset the (x,y) location to the Emitter's origin point. D'oh!

The problem was on my end: I was removing the DisplayObjects from the Display List prior to adding them to the list. This caused the prior offset to disappear; the system assumed global coordinates in the localToGlobal() function call. Whoopsie!

That said, I've expanded the code "fix" I had above to the following (this is the whole function):

private function addDisplayObject( obj:DisplayObject ):void
{
	var particle:Particle = _particleFactory.createParticle();
	var len:uint = _initializers.length;
	for ( var i:uint = 0; i < len; ++i )
	{
		_initializers[i].initialize( this, particle );
	}
	var displayObj:DisplayObject = DisplayObject( _renderer );
	var r = DisplayObjectUtils.globalToLocalRotation( displayObj, DisplayObjectUtils.localToGlobalRotation( obj, 0 ) );
	if (obj.parent)
	{
		var p = displayObj.globalToLocal( obj.localToGlobal( new Point( 0, 0 ) ) );
		particle.x = p.x;
		particle.y = p.y;
		obj.parent.removeChild( obj );
	}
	else
	{
		particle.x = obj.x;
		particle.y = obj.y;
	}
	particle.image = obj;
	particle.rotation = Maths.asRadians( r );
	_particles.unshift( particle );
	_renderer.addParticle( particle );
}

That works for my purposes. I'm not sure if it's the correct default behavior (puts freshly created [read: no modifications to x/y/etc values] DisplayObjects at the renderer's origin point instead of the Stage's origin point).

Thoughts?

Single Image Particles at Specific Locations

Richard — Mon, 19 May 2008 15:55:05 +0100

That looks sensible, so I've added it to the code. My only change is to also make the globaltoLocalRotation conditional on the object having a parent. Thanks.

Single Image Particles at Specific Locations

ericr — Mon, 19 May 2008 23:36:21 +0100

Sounds good! Good point about the rotation, too. I'm not worried about that yet (though may very well be soon) and hadn't put any thought towards it. Nice!