Nick Petit
npetit
About Me
Connect
LOCATION
Not Specified
WEBSITE
Houdini Skills
Availability
Not Specified
My Badges
SideFX Staff
Since Feb 2008
Recent Forum Posts
Need help with very simple fracture/explosion/RBD solver May 21, 2026, 7:52 a.m.
Here's an example. When the columns move between the 2 posts, it deletes the outer constraints to let the pieces fly in all directions with an initial force applied to the pieces.
To do that it first needs to find the pieces attached to the constraints' anchor points as the constraints themselves don't actually move during the sim.
It uses 2 wrangles in a sop solver which allows you to access both the constraint geometry and the rbd pieces geo, one to delete the constraints - it needs access to the rbd pieces as mentioned above - and the other simply adds a random force attrib to the rbd pieces.
To do that it first needs to find the pieces attached to the constraints' anchor points as the constraints themselves don't actually move during the sim.
It uses 2 wrangles in a sop solver which allows you to access both the constraint geometry and the rbd pieces geo, one to delete the constraints - it needs access to the rbd pieces as mentioned above - and the other simply adds a random force attrib to the rbd pieces.
RBD Car Rig, How to Add Custom Animation? May 20, 2026, 9:34 p.m.
If you have an example hip you can share here or through support I can take a look. It's hard to tell what's going on without that unfortunately.
RBD Paint issue: Shows strokes but doesn't apply May 20, 2026, 4:04 a.m.
The node caches the output to speed things up. What this means however is if the input changes, you need to re-apply the strokes.
In the Geometry tab, when you enable or change the division size, it updates the topology based on the input geo, so it reloads the input and reapplies the strokes.
In order not to pollute the output unecessarily, the extra divisions and the vis_falloff attribute are added to the geometry fed into an output node for display only.
Houdini HDAs and subnets can have Output SOPs with negative indices. These won't show up as outputs on the node, but you can still set the node's Output for View Flag to point to their negative index, telling the viewport to show the geometry connected to that Output SOP instead of the geometry coming out of the outputs visible on the node.
When the node is created or loaded, a callback script is executed which sets the node's outputforviewflag to -1.
This should be visible in the network view.
Normally, to switch display between outputs, you can right click on the node and under Flags > Output for View, choose one of the outputs. However, the negative index outputs aren't listed.
What seems to happen is you are switching output for view flags on the node which then shows the default output geo without the visualiser attribs. Unfortunately, and this is a bug, the node only sets its outputforviewflag back when the hip file is loaded again, which isn't ideal.
You can set it back with a bit of python:
Or, instead of relying on the visualiser of the hidden display node, you can visualise the painted attribute directly
In the Geometry tab, when you enable or change the division size, it updates the topology based on the input geo, so it reloads the input and reapplies the strokes.
In order not to pollute the output unecessarily, the extra divisions and the vis_falloff attribute are added to the geometry fed into an output node for display only.
Houdini HDAs and subnets can have Output SOPs with negative indices. These won't show up as outputs on the node, but you can still set the node's Output for View Flag to point to their negative index, telling the viewport to show the geometry connected to that Output SOP instead of the geometry coming out of the outputs visible on the node.
When the node is created or loaded, a callback script is executed which sets the node's outputforviewflag to -1.
This should be visible in the network view.
Normally, to switch display between outputs, you can right click on the node and under Flags > Output for View, choose one of the outputs. However, the negative index outputs aren't listed.
What seems to happen is you are switching output for view flags on the node which then shows the default output geo without the visualiser attribs. Unfortunately, and this is a bug, the node only sets its outputforviewflag back when the hip file is loaded again, which isn't ideal.
You can set it back with a bit of python:
hou.node('/obj/geo1/rbdpaint3').setOutputForViewFlag(-1)
Or, instead of relying on the visualiser of the hidden display node, you can visualise the painted attribute directly