Hi again everyone,
I'm following a tutorial involving mixing procedural anim and rbd sims, but I'm having issues with the ground plane, and I'm generally confused as to why the simulation looks different outside of the dopnet.

So, to clarify, when I'm inside of the dopnet, everything looks great and works fine.
When I move one level up, the simulation changes. This shows at about frame 10, precisely when the bottom cube hits the ground plane, that ground plane then starts to rise up and everything is screwed from that point onwards.

I've attached the hipnc file which should be set to display the dopnet (the level at which everything is screwed). Go into the dopnet, and all is well.

Any thoughts? I'm stumped.

No ideas at all? I can't really continue with my tutorials until this is figured out

If you use obj merge option in dopnet node to import boxes and groundplane separately then there is no movement in groundplane.
But don't understand why there is a movement when everything is imported using one single dopnet nod. If you check the position data of groundplane , it dose not show any movement.

Hi sadhu, and thanks for the reply.

However, I don't quite understand what you mean. I have my
obj > setup_animation > dopnet1 node that has the ‘Enable’ checked on the Object Merge tab. Is that what you are referring to? If I turn this off I can see nothing at the obj > setup_animation level.

In dopnet1/object merge/ object - type box_*
dopnet1/object merge/ Data - type Geometry
This will just import Geometry data of all the box objects.

Similarly if you just create a copy of this dopnet node and use it to import groundplane Geometry and then merge the output of two dopnet node then there is no movement in ground plane.

In dop if you change the sequence of connection to the merge node, connect groundplane last, is giving the desired result. But again dont understand why it dosent work otherwise.

Thanks for the help sadhu.

Unfortunately, neither method really works for me. I don't really want to cull the floor using the box_* mask - besides, the cubes still act like they are being pushed up by the ground plane.
Changing the input order for the merge in the dop network doesn't work for me either. The plane doesn't rise up, but it still moves along the xz plane, and boxes penetrate it all the time.

It looks like this whole scene is screwed and I'm going to have to start over from scratch
It better work this time…

…well, I rebuilt the scene from scratch, and the behaviour is exactly the same. I also tried pluging the ground plane into a static solver, but didn't work either.

There is nothing I can do to stop the grid from rising and acting completely different to when viewing inside the dopnet.

I have to say this is deeply frustrating and has shaken my confidence in Houdini and/or my own abilities. I'm wondering if it's worth continuing with Houdini at all if I cannot get a simple grid to stay still.

EDIT : Oh I found the source of the problem, the order used in the merge node is actually really important and represent the order in which objects will be processed. It feels crazy I never noticed that before.


I am wondering if someone found a solution to this because I am having the exact same problem. Nothing seems to interact with ground-plane in dopnet no matter what I try when it is working well in pre-made nodes like rbdbulletsolver.

It's been a month everything was fine, I tried installing new 19.5, rebooting pc but nothing helped.