Is there a way to replicate objects on top of each other with collision.

You can do it but you will first need to convert the first set of replicated objects into "Real Instances" and then use the surface replicator or the regular replicator for the next set. 

Depending on the number of replicated objects, it is very easy to overburden the program. 

Ah, I see what's going on. For stuff like this, you need to set the minimum replication distance to be equal to the dimensions of the object being replicated. 

Now, if you are trying to create a pile of these things that cross each other but don't intersect, then you'll need to first change the Motion to Physics on the source object, do what I mentioned above,  add a couple of layers in the Z axis, convert to Real Instances and then engage the physics and run a simulation.

Ok I'll give it a try I am just starting to use Carrara 7. Thanks

Boy am I lost.

Yes but I can't seem to get my head around it. Sorry to sound so dumb.

The first thing to do is to select your individual object and determine it's size. This will be used to create the minimum offset of the grid for replication. (we don't want things to overlap)

Click the images if you need to see them larger.

Then, I move the original replicator group well above the duplicated "real instances", turn off the physics of the source object and then disable visibility for both the source object and the original replicator group. (this option is in the Properties Panel)

The original Replicator group is moved above the new real-instances group so it won't interfere with the physics. It's hidden just so it won't be seen. But I don't delete it in case I need to go back and make changes that for a new real-instances group. 

Additionally, physics, especially with more complex shapes like the "S" shape may need some of the physics properties adjusted to interact with each other correctly. This is performed in the Scene portion of the Properties Tab - it's best to adjust only the Geometry Fidelity tab first, even up to 100%, before moving the other sliders. 

Hope this helps!

Thanks I will be doing this today. I thank you very much Mark.I post my results.

This is where the tweaking of the physics settings comes into play. I suspect you already increased the Geometry fidelity settings mentioned earlier.

There are two things to try here in the following order:

1. subdivide/add more polygons to the plane  that is the floor - increasing this by a factor of 2 or four would be a good start. The additional Polygons and vertexes help the Bullet physics engine figure out what to do. (if you are using an older version of Carrara - v7 or earlier - then the physics will be more difficult to tweak since the Bullet library  <Carrara v8+>
   is much, much better than Carrara's original implementation)

2. Incrementally increase the collision fidelity above 100% - this will begin to significantly increase the calculation time.

I'm using Carrara 7 (not Pro) Here is a video short of my progress.

http://uncle808us.blip.tv/file/5094073/

I really appreciate you helping me with this.

It looks like you've got everything working correctly. Now it's just a matter of adjusting - and this might take a little while in C7. First Recreate the replicator group but this time, dial down the "bounce" of the source object to 1-5% and see how that treats you. 

I'm working on it....

Takes a long time to run physics.But they are laying on the plane now I wonder how long it will take. LOL

Glad it's coming together.

If you find yourself doing regular physics calculations, it is totally worth it to upgrade Carrara. The Bullet physics are soooooo much faster. 

Mark

I'd do it but it's a lot of money. I'll have to talk it over with the wife.

I got it to work and now understand a lot more than I did. Thank you for your help.

Fantastic. Thanks for the status update.