# Thread: Get reaction force/torque?

1. ## Get reaction force/torque?

I've been fooling around with CF2.5 and was curious if I would be able to make an engine similar to this one which I made with C++ and Box2D years ago. Having it in CF2.5 would be great as it'd then be much quicker to make an actual game with.

In my engine, I used revolute joints (or possibly weld joints) to join together various objects. When the reaction force or torque went beyond a certain amount, I'd just break the joint, which resulted in a very nice destructible terrain effect.

According to the Box2D documentation the functions needed to get these values are GetReactionForce() and GetReactionTorque(). Is there a way in CF2.5 to retrieve the value of these functions?

If not, is this a planned feature?

And if not, then I'm wondering, is there a way to tease a b2RevoluteJoint* out of CF2.5 via a C++ extension?

Thanks!

2. Please add this to the feature request list in bugbox.clickteam.com
For the moment, I am getting rid of the bugs of the first version. I will, when things get calmer, make a pass on all the suggestions and implement them. It was very difficult for me when designing the Box2D features of Fusion 2.5 to plan all the things that user would want.

3. Getting current force of an object would be awesome. In the meantime, is there a way to set a maximum applied force to an object?

4. Hi Francois,
OK, I've added this to the feature request list. It's awesome that you guys are supporting the software to this extent! The bug and feature request tracking is a wonderful idea.

@helli, I was talking about the force on joints; however, I'd imagine you can get the force applied to an object by comparing its current velocity to last frame's velocity. Take this difference in velocity (i.e. acceleration in pixels per cycle^2) and multiply it by the mass of the object (F=ma) and that will give you force (in kilogram pixels per cycle^2).

Limiting the acceleration of an object would have the same effect as limiting the force; just figure out the difference in velocity. If it's above a certain amount, clamp the velocity so it's as if less force/acceleration was applied to the object.

5. I'm not sure how I'd get the object's currenct velocity, can't find the option anywhere.

6. Does anyone know of a way to get an object's velocity?

7. African or European? Oh wait...

8. What? ^

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•