Hello guys I was wondering is there a way to control the wire object with custom forces in vopsop like SDF attraction. Like attracting curves to an goal object.

sabotage3d
Hello guys I was wondering is there a way to control the wire object with custom forces in vopsop like SDF attraction. Like attracting curves to an goal object.

Custom forces can be specified by creating an attribute called “fexternal” on the Wire Object's “RestGeometry” subdata (described on the Wire Object DOP's help page). The force values could be updated at each time step using a SOP Solver. Attached is a simple working example.

Thank you Derrick. It's the good example, I didn't know that it is possible.

Thanks but I still cannot understand why do I have to use the sop solver because I can assign this attribute in a sop level and it seems it is working is there any difference.

you can define fexternal in source geo for some arbitrary forces, you can even animate it as well as source wire and it will affect the wiresim

however SOP solver method will give you the ability to calculate your fexternal force based on simulated wire from previous frame, which may be crucial if you want to match certain goal

hello

It seems like in H 15, fexternal is not taken into account by Wire solver. ( @derrick file doesn't work anymore)
in fact I need the wire solver respect the external force.

I have a piece of object and a simple wind force and I want it to rotate the object towards to moving direction.
I don't know hod to do it … ( does Orient attribute help?)
please let me know how to do it in H 15.

thank you in advance

any help would be appreciated!

Attached is an updated example that will work with Houdini 15.0. Basically, the Wire Object in Houdini 15.0 was updated to make some workflows easier and more consistent with other solvers. Instead of using the “fexternal” and “texternal” point attributes to apply forces and torques to Wire Objects, use “force” and “torque”. Also, the Wire Object now only has a single geometry subdata. The Wire Solver expects to find the attributes on this piece of subdata.

derrick
thank you very much for your time and file