box2D: B2RayCastCallback class missing

MadNukin · December 20, 2017, 5:23pm

Hello again.
As the title suggests, B2RayCastCallback class is missing from https://github.com/openfl/box2d
I’m following this tutorial: http://www.iforce2d.net/b2dtut/world-querying
and at one point they want me to extend b2RayCastCallback which doesn’t exist.
If anyone experienced with box2d could help me out on how to work around this problem, that would be fantastic.

singmajesty · December 20, 2017, 7:38pm

Hi!

I think we’re using a Haxe function type for the callback, here:

github.com

openfl/box2d/blob/3a7942157f331ce83cf40229c484d124acd0fb67/box2D/dynamics/B2World.hx#L882


	 * fraction:Float       // The fractional length along the ray of the intersection
	 * ):Float
	 * </code>
	 * Callback should return the new length of the ray as a fraction of the original length.
	 * By returning 0, you immediately terminate.
	 * By returning 1, you continue wiht the original ray.
	 * By returning the current fraction, you proceed to find the closest point.
	 * @param point1 the ray starting point
	 * @param point2 the ray ending point
	 */
	public function rayCast(callbackMethod:B2Fixture -> B2Vec2 -> B2Vec2 -> Float -> Dynamic, point1:B2Vec2, point2:B2Vec2):Void
	{
		var broadPhase:IBroadPhase = m_contactManager.m_broadPhase;
		var output:B2RayCastOutput = new B2RayCastOutput ();
		function rayCastWrapper(input:B2RayCastInput, proxy:Dynamic):Float
		{
			var userData:Dynamic = broadPhase.getUserData(proxy);
			var fixture:B2Fixture = cast (userData, B2Fixture);
			var hit:Bool = fixture.rayCast(output, input);
			if (hit)
			{

so you could try passing a function like:

function rayCastCallback (fixture:B2Fixture, point:B2Vec2, normal:B2Vec2, fraction:Float):Void {
    ...
}

MadNukin · December 21, 2017, 4:53am

function rayCastCallback (fixture:B2Fixture, point:B2Vec2, normal:B2Vec2, fraction:Float):Float{
    ...
}

Thanks, just needed to replace the return value from Void to Float.

singmajesty · December 21, 2017, 5:43am

Oh, yeah! Dynamic, not Void. I wonder if it always returns a Float, or if it ever returns something else?

MadNukin · December 21, 2017, 3:36pm

From all the tutorials I’ve read on this subject it seems like this function should return Float.
http://www.iforce2d.net/b2dtut/world-querying
http://www.learn-cocos2d.com/api-ref/1.0/Box2D/html/classb2_ray_cast_callback.html
and on page 60 of the official manual for box2D:
http://box2d.org/manual.pdf
And I think if you return some other class, it will be registered as returning 1, which is the best option for the function to work properly.

Again, thanks a lot of the help.