Stiff Joint

[Carli]

Hi.

How can i implement a joint that connects two bodys to a stiff unit?

[JernejL]

A compound collision works best for such cases..

[PJani]

or you can create custom rigid joint...

[JernejL]

or you can create custom rigid joint...

Julio advised against it, solving a rigid joint is difficult and won't work as precise and fast as the compound collision can.

[Carli]

A compound collision works best for such cases..

But i can't stack them!

[kallaspriit]

What do you mean by stacking, you can add several collisions to a compound.

[JernejL]

A compound collision works best for such cases..

But i can't stack them!

They should stack just fine, show what's the problem.

[Carli]

with stacking i ment the recursive compound collision.

[JernejL]

But you can add pieces from 1 compound to another.. that is no problem.

[PJani]

It would be nice if would be possible to add or remove compound collisions at run time:)

[JernejL]

It would be nice if would be possible to add or remove compound collisions at run time:)

You can.. by rebuilding it, it is very fast actually..

[PJani]

It would be nice if would be possible to add or remove compound collisions at run time:)

You can.. by rebuilding it, it is very fast actually..

I never consider that option.

[Carli]

But I do really need a stiff joint!

I want to attach a null-collision-body to an other body. A clever answer like "use a compound collision" is trash.
Or do I need to delete the body from the world and set the relative matrix myself each frame?

[JernejL]

But I do really need a stiff joint!

I want to attach a null-collision-body to an other body. A clever answer like "use a compound collision" is trash.
Or do I need to delete the body from the world and set the relative matrix myself each frame?

You can change body's collision at runtime without destroying the body, the function to achieve this is named NewtonBodySetCollision.

A few topics about this:

viewtopic.php?f=9&t=5558&p=40089&hilit=rigid+joint
viewtopic.php?f=9&t=5181&p=36956&hilit=rigid+joint
viewtopic.php?f=15&t=4056&p=27525&hilit=rigid+joint (example rigid joint implementation)

But if you consider my answers trash then i can stop trying to help you, i suggested you a working solution to a problem that came up on the forum several times already and Julio himself suggested compounds, compounds are also much more optimized in this regard and won't put as much strain on cpu usage, i'm using them in one project to simulate complex spaceship shapes, and the performance and speed is faster than what i expected. You cannot put a compound in compound - yes, but that's a small issue, which you can easily resolve with very little matrix math.

[Carli]

It would make no sense - i would add a null-collision to a compound and i even do not have two different matrices (which i need for graphics)

there are two other solutions for me:
- removing one object and setting the matrix myself each frame without a newton body
- changing the whole network code because the object will not longer exists but still has a graphical body

--> A stiff joint would be much easier and i do not have to make any workaround
plus i can some other things like attaching a body to another dynamically