Hi all!

How do I get the vertical position in space of a falling rigid body object? For some reason the “translate x” position doesn't update if an object is a rigid body. Help anyone?

Thanks!

Houdini's y up so I'd be looking at the dop object's Position/Options t sub-data.

You will have to add the p pivot channel to the t to get the world space position of your RBD object.

Got any idea what node I can find that in? Or would I need to create a new node for that?

(Attached is a simple falling object.)

DOPs doesn't update the actual object's translate parameter. It's the DOP Import SOP that fetches the simulation results from the DOP network and applies it directly to the geometry.

There are several ways to get at the actual animation values for the RBD object in the simulation.

1) You can use the Dynamics CHOP to fetch the simulation results. Follow the Dynamics CHOP with a Delete CHOP to isolate the *:t?, *=p? and *:r? or translate, rotate and pivot channels.

2) You can fetch the channels directly with the dopfield() expression like this:
dopfield(“/obj/AutoDopNetwork”, “box_object1”, “Position”, “Options”, 0, “tx”)
dopfield(“/obj/AutoDopNetwork”, “box_object1”, “Position”, “Options”, 0, “ty”)
dopfield(“/obj/AutoDopNetwork”, “box_object1”, “Position”, “Options”, 0, “tz”)

Hey Jeff could you be so kind and post a simple example of that?
I never really dealt with chops, so I have no clue

thanks,

Manuel

Yes, pls. Can you provide an example, Jeff? Thanks!

here it is. There's quite some material on chops at SESI's website.

Cheers

^Awesomeness! Thanks Rafaels!

that's really useful, thanks for the file man!!

cheers!

Follow up question: What if you have 2 falling objects? Would you need to create another chopnetwork? It seems that only a single “export” node can be activated at any given time inside a chopnetwork.

Any ideas?

You can import and export multiple channels at once but if you're exporting to, say, the translateY of another geo it won't be of much help, since as I understand only the first channel would be used.
Another way of doing things would be either using the channel SOP, or the chop() expression function.

well you could go back to use the dopfield expression, work in a SOP Solver and stamp your $OBJID variables in order to treat objects seperately !!!!

asnowcappedromance
well you could go back to use the dopfield expression, work in a SOP Solver and stamp your $OBJID variables in order to treat objects seperately !!!!

Can you make a simple HIP file example of that? (pls?)

actually, you don't really need a SOP Solver in this case, in order not to make it too complicated, here's an example using the foreach node to access the position coordinates in world space.
check it out!

Manu