[Sidefx-houdini-list] Several SOPs in a SOP Path parameter

rmagee at sidefx.com rmagee at sidefx.com
Fri Oct 19 10:50:56 EDT 2007

The biggest difference between H8 and H9 that affects this lesson is that
when you create an RBD object in H8 it is imported into the dopnet and the
resulting simulation resides in that dopnet leaving the original objects
as they were.

For H9, an object that is turned into a RBD object in dops, has a
dopimport sop added to it at the geometry level. The simulated motion on
the rbd object in dops is fed to the original object at the geometry
level. You therefore only have control of that object at frame 1 then the
dopimport sop takes over.

The implications for the table demo are that in H8 we could import two or
three objects into a single RBD object and we didn't need to worry where
the simulated motion was being sent. With H9 the dopsop is important.
Therefore if I were to recreate this lesson for H9 (which I am looking
into doing for video) then I would probably select the objects that I want
to "stick" together and choose Combine from the Modify menu before turning
them into an RBD object. This way there would be a single piece of
geometry that would be simulated in dops then driven by the dopimport sop.

The reason for sending this information back to the original object was to
let these objects play a role in the final rendered output. It is harder
to assign materials and set up render properties such as motion blur on
the dopnet itself. It is better to use the original object with the new
motion imported in.


> Hi again, François
> Francois Duchesneau a écrit :
>> Sorry, I was wrong and you're right, yes you can have more than one sop
>> in
>> that field, even in H9 but it won't work as it used to be because of the
>> new way the rigid body creation are done in the viewport.
> I tried to adapt the tutorial to the H9 way.
> So, as my 4 objects were table legs, instead of take all of them, I just
> took one, centered at the origin, and in the "RBD Object" DOP, I set
> "Number of Objects" to 4.
> Next I use expressions in the X & Z fields for the translation, to place
> my table legs at the corners of the table. Everything seems OK.
> I also created a very "RBD Object" DOP, calling a sphere SOP. Its Y
> position is set in the DOP.
> When I merge these two DOPs, with the "sphere DOP" as first input, one
> of my table leg disappear. If I invert the input, the table leg comes
> back...
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