The Box2DExample class linked above uses spineboy and box2d. It is up to date and should run out of the box. It works by creating physics bodies to match the images. This could be improved by using bounding boxes when that is released in a few days, which means you won't have so many physics bodies. Each frame the physics bodies are updated to match the animating skeleton. If you want a ragdoll effect, just stop updating their positions and let gravity in the physics simulation take over.

Hi Kate,
I think you'll have to manually flip the body in the world when you flip the character.

And the falling down stuff gets complicated, like building joints between the bodies and letting the bodies drive the position of the bones rather than the Spine animation.

I'd love to have instant ragdoll creation build into Spine, but I think it's a bit beyond what we can expect an animation tool to provide.

well for the falling, I'd think you'd want a separate body and have it be a dynamic body and have it drive the skeleton position, then use a filter group to keep it from colliding with the skeleton's body.

as for flipping the body.. Im afraid I dunno.. my character only goes to the right

I went down this same path. Box2D has no transforms like what you want to do to flip it. I think there are basically two approaches used elsewhere and those are:

• maintain two separate bodies, one for going left and one for going right and just activate/deactivate them as needed
• destroy/recreate the fixtures when changing direction

Neither are really ideal, and I am not experienced with box2d either, so I may be wrong here, so I'd also be happy to hear any solutions others have used.

KateTheAwesome escribió

Yea I sat down a bit and tried to manually flip the bodies, read up about how stuff is usually flipped but then gave up after a while.

I have the same problem with flipping. The angle of the flipped body is incorrect. Maintain two separate bodies isn't excellent decision.

Ok, I've solved this issue.
My solution consists of two steps.

FIRST: Create attached bodies with zero center (0,0) and zero rotation.

for (Slot slot : skeleton.getSlots()) {
			if (!(slot.getAttachment() instanceof Box2dAttachment)) continue;
			Box2dAttachment attachment = (Box2dAttachment)slot.getAttachment();
			PolygonShape boxPoly = new PolygonShape();
		
	        boxPoly.setAsBox(attachment.getHeight() / 3 * attachment.getScaleX(),
			attachment.getWidth() / 3 * attachment.getScaleY()); //NO MORE CENTER AND ROTATION			
		BodyDef boxBodyDef = new BodyDef();
		boxBodyDef.position.x = skeleton.getX() + slot.getBone().getWorldX();
		boxBodyDef.position.y = skeleton.getY() + slot.getBone().getWorldY();
		boxBodyDef.type = BodyType.KinematicBody;
		attachment.body = world.createBody(boxBodyDef);
		FixtureDef fd = new FixtureDef();
		fd.shape = boxPoly;
		fd.isSensor = true;
		attachment.body.createFixture(fd);

		boxPoly.dispose();
	}

SECOND: In animation mode, transform body linked with the center of bone and with bone rotation.

for (Slot slot : skeleton.getSlots()) {
		if (!(slot.getAttachment() instanceof Box2dAttachment)) continue;
		Box2dAttachment attachment = (Box2dAttachment)slot.getAttachment();
		if (attachment.body == null) continue;
		float x = skeleton.getX() + slot.getBone().getWorldX();
		float y = skeleton.getY() + slot.getBone().getWorldY();
		float rotation;
		if (inverse) { //invert body rotation when moves left
			rotation =180 - slot.getBone().getWorldRotation() ;
		} else {
			rotation = slot.getBone().getWorldRotation() ;
		}
		
           //deltaX and deltaY are the coordinates of the end of the bone
	float deltaX = (float)(slot.getBone().getData().getLength() * Math.cos(rotation*MathUtils.degRad));
	float deltaY = (float)(slot.getBone().getData().getLength() * Math.sin(rotation*MathUtils.degRad));

           //FINALLY TRANSFORM
	attachment.body.setTransform(x + deltaX/2, y + deltaY/2, rotation*MathUtils.degRad);
	
}

Now you have just one problem: all bodies have the attached TextureRedgion size and rotation. So, you may change body sizes of the concrete bodies. This solution used shapes once created. You don't need to reinitialize the shapes or change the body's parameters.

It would be cool if Nate implement this feature in the Spine. Attaching physics bodies in Spine editor, and then simply used them in runtime.

Now you have just one problem: all bodies have the attached TextureRedgion size and rotation. So, you may change body sizes of the concrete bodies. This solution used shapes once created. You don't need to reinitialize the shapes or change the body's parameters.

yeah but also they aren't dynamic bodies and you have N° bodies for each skeleton . it depends which approach you want to use : Box2d driven by Animation or Animation driven by Box2d or a mix of two like in my case. Anyway your solution is simple and clean ! well done

bye

Hi,

Btw, when you want to add BoundingBox, do you add it as a new node or as an attachment ?

Also what is the proper way to tie box2d body to sprite ?

BR