Fisica: accessing the underlying org.jbox2d.dynamics.Body object?

pointfive

Fisica: accessing the underlying org.jbox2d.dynamics.Body object?

in Contributed Library Questions • 2 years ago

I've begun using Fisica because I ran into problems with Boxwrap2D not rendering on Android. Anyway... I have a quick (and hopefully not too noob-ish) question.

How might I go about accessing the underlying Body (org.jbox2d.dynamics.Body) object of an FBody (Fisica.FBody)? FBody doesn't extend Body, so I'm not sure how Richard is leveraging/interfacing with the JBox2D library. I'll start digging through the Fisica source code now to figure this out, but would appreciate the guidance of those wiser than me.

My reasons? While Fisica is great, I'd prefer to do most of my work with Vec2, and it seems there aren't many Fisica methods for this. For example, I find:

Vec2 location = Body.getPosition();

...preferable to the FBody alternative of:

Vec2 location = new Vec2(FBody.getX(), FBody.getY());

Also, I'd like to call certain methods such as Body.applyImpulse() which don't seem to have Fisica equivalents.

Am I on the wrong path? Making a big, dumb mistake or two? Thanks in advance for the steer.

Replies(3)

ricardmp

Re: Fisica: accessing the underlying org.jbox2d.dynamics.Body object?

2 years ago

Hi,

Yes you'll need to access the underlying Body of FBody. Currently the only way is inheriting from the FBody and then you can access from inside that class, the member Body m_body. You need to inherit because that member is protected, but I might soon make it public so that people don't get stucked.

Another option is to let me know your needs and I'll add them to Fisica (e.g. I just added a TODO item for the applyImpulse() method).

The Vec2 is a bit more sensible, since I didn't want to add yet another vector class to the class hierarchy. I have thought of using PVector instead, but haven't made a decision yet, not sure if it really is a good option.

pointfive

Re: Fisica: accessing the underlying org.jbox2d.dynamics.Body object?

2 years ago

Thanks, Richard... this is helpful.

I've set my class to extend FBody, but I haven't had any luck accessing the Body object. I either get a NullPointerException, or a message that says "m_body is not visible". I'm hopeful I'm just making a silly mistake, but after hitting my head on it all morning, I've decided to take a rest. I'll see what I can get done with the methods that you've already put in FBody.

Regarding vectors, I'll cast my vote for Vec2 over PVector. I find the add()/mul()/etc. methods to be preferable to their PVector equivalents.

And thanks for adding applyImpulse() to your TODO. I would also find Vec2 getPosition() and Vec2 getVelocity() useful, as well as Vec2 versions of pretty much anything that currently has (float x, float y) arguments (e.g., void addForce(Vec2 force), void setVelocity(Vec2 velocity), etc.)

Again, thank you, sir!

ricardmp

Re: Fisica: accessing the underlying org.jbox2d.dynamics.Body object?

2 years ago

Try getting the new Fisica release (0.1.9). I have added a FBody.getBox2dBody() so you can access the Body.

However I still haven't done or decided to do the getVelocity() getPosition() etc... but I will think about it a bit more. In the meantime you can always inherit and implement your own versions using getX(), getY(), ... etc.

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