How to make a dumbbell ?

[wissme]

Hi !
I am just starting to try Chipmunk (old version, around 2.5, please don't tell me to use another more recent version, I'm not in C and use a special FFI). I want to make a dumbbell, so I make two balls and I join them by a joint. But the joint acts as a spring. I would like it to be rigid. How can I do that ? Thanks a lot !
-w

[slembcke]

[wissme]

You tell me to do 1 body and several shapes ?
But in my case, I have 3 bodies, right ? Two balls and a segment.
Should I add one shape around them ?

-w

[slembcke]

What you want is to have 1 body and 3 shapes then. What you want is 1 single rigid object, you represent that creating one rigid body and giving it a shape by adding a few collision shapes for it.

[wissme]

Well, I still don't see. Maybe can I narrow the problem to having a ball with a rigid stick firmly attached.
What would I use to build the body ? cpMomentForCircle ? cpMomentForSegment ?....
Could you show me the C code ? It's probably a snip when you know the software, but my ideas are not that clear. That should give me a start...
Thanks !

-w

[slembcke]

[wissme]

Thanks a lot, I appreciate very much ! I will translate this in Scheme :

(define offset 10.0)
(define center1 (cpv offset 0.0)
etc.

By the way, Jay McCarthy has done an FFI interface with your C API to be used with Racket (http://racket-lang.org) which is the major dialect of the Scheme language. His port should be in :
http://planet.plt-scheme.org
but I don't see it today, maybe is he updating the (old 2.5) port to latest Chipmunk version ?... You will find something there :
http://planet.plt-scheme.org/display.ss ... hangerep=2

[wissme]

I forgot : do you mean I will have no joint do define ?...

[slembcke]

No joints. You just have one body, so there is nothing to join together.