[Sidefx-houdini-list] How to control RigidBody instances

Ciaran Moloney moloney.ciaran at gmail.com
Tue Nov 28 12:38:15 EST 2017


If you're working in a wrangle node, you could just reference the input
port and be done with it.

On Tue, Nov 28, 2017 at 4:59 PM, Michael Dunkley <mdunkley at gmail.com> wrote:

> Hey Thomas - the null thing i mentioned isn't required per se, just
> best practice and a very common houdini pattern.  Basically the idea
> is you usually want to reference paths from nulls, if appropriate, so
> that if your network graph changes (ie you add more relevant
> operations after your wrangle), you don't have to change the
> expression.  I guess the idea is that it makes your logic more
> agnostic and less reliant on specific nodes.  My personal approach is
> to label the nulls in ways that describe the state of the network at
> that point (eg OUT_sim).   Again, not strictly necessary, just a
> little cleaner than referencing workhorse nodes, and also works better
> in cases where, for instance, you decide you want to cache the output
> of your dop network before referencing it.
> For your case i think the network would look something like
> dop_import->null, and you'd then reference that null.
>
> On Tue, Nov 28, 2017 at 11:14 AM, Thomas Volkmann <listmail.3d at gmail.com>
> wrote:
> > Hi Michael, that works great! The shelf tools seem to do the packing
> > automatically (copy stamp node).
> > What do you mean by pulling from a null sop?
> > So far I can point directly to /DopNetwork or use a merge node to get it
> > inside my Geo where I connect it to the wrangle-node (was just about to
> > test Oliviers approach when your mail came in...thanks Olivier I'll take
> a
> > look at that approach in due time).
> > It's a lot of these 'best practices' that I'm not aware of atm....
> >
> > cheers,
> > Thomas
> >
> > On Tue, Nov 28, 2017 at 4:32 PM Michael Dunkley <mdunkley at gmail.com>
> wrote:
> >
> >> Hey Thomas.  So far as your expression goes - P is usually a point
> >> attribute, not a detail, the detail function doesn't require "op"
> >> syntax, and usually doesn't return an array unless you're asking for
> >> an array attribute.
> >> The expression you're looking for is probably more along the lines of:
> >>
> >> vector pos = point("/full_or_relative_path/to_node","P",3)
> >>
> >> where the path is just a normal houdini path, the attribute is
> >> expressed as a string (as you had) and the 3 is simply the number of
> >> the rbd you're trying to access.  This is making the assumption that
> >> you're working with packed rbd's, so that the "point number" you're
> >> grabbing actually represents an entire packed piece.  Unpacked rbd's
> >> would be slightly trickier to grab.  Haven't watched that Entagma vid,
> >> so i don't know which you're actually working with.
> >> It would also be good practice to pull from a (null) sop if possible
> >> (as opposed to dops directly - pulling directly from dops is certainly
> >> possible, though the syntax is a little screwier and generally not
> >> ideal).
> >>
> >>
> >>
> >> On Tue, Nov 28, 2017 at 9:05 AM, Olivier Jeannel <
> facialdeluxe at gmail.com>
> >> wrote:
> >> > I personnaly go with vop.
> >> > Having the points you're working with in the first port.
> >> > And the points you're gathering infos from in the second port.
> >> > You can either use a PcOpen + Pcfilter (P) if you want to get the P
> >> > according to the distance.
> >> > Or use the Import Point (P) based on the id number.
> >> >
> >> > Or go the PrimUV route if you want to gather one attribute from
> polygon
> >> > location (same as UV to Location in ICE)
> >> >
> >> >
> >> > 2017-11-28 13:46 GMT+01:00 Thomas Volkmann <listmail.3d at gmail.com>:
> >> >
> >> >> A small follow-up:
> >> >> How do I get the position of a certain RigidBody instance in another
> >> >> objects pointwrangle?
> >> >>
> >> >> I'm trying:
> >> >> vector pos[] = detail("op:/MyDOP/MyRBD_PackedObject", "P");
> >> >>
> >> >> Any hints?
> >> >> Thanks,
> >> >> Thomas
> >> >>
> >> >> On Mon, Nov 27, 2017 at 2:27 PM Thomas Volkmann <
> listmail.3d at gmail.com>
> >> >> wrote:
> >> >>
> >> >> > Excellent, Thanks!
> >> >> >
> >> >> >
> >> >> > On Mon, Nov 27, 2017 at 1:29 PM Matt Estela <matt.estela at gmail.com
> >
> >> >> wrote:
> >> >> >
> >> >> >> Grow/shrinking is well covered by this entagma tutorial:
> >> >> >>
> >> >> >> http://www.entagma.com/scaling-the-bullets-dynamically/
> >> >> >>
> >> >> >>
> >> >> >> On 27 November 2017 at 23:10, Thomas Volkmann <
> listmail.3d at gmail.com
> >> >
> >> >> >> wrote:
> >> >> >>
> >> >> >> > Hi,
> >> >> >> >
> >> >> >> > I'm taking another dive into Houdini again and I'm having a very
> >> slow
> >> >> >> start
> >> >> >> > at the moment. It seems I have forgotten some of the basic
> >> stuff....
> >> >> >> > So if someone could help me out and save me a couple of hours it
> >> would
> >> >> >> be
> >> >> >> > much appreciated.
> >> >> >> >
> >> >> >> > I have a simple RigidBody simulation from some instanced
> objects.
> >> >> >> > Now I would like to do some stuff with some of these, like
> select
> >> by
> >> >> ID
> >> >> >> and
> >> >> >> > then putting them to sleep at a certain frame or have them
> >> >> >> > growing/shrinking over time.
> >> >> >> >
> >> >> >> > Can I do that stuff all in the same place (some wrangle node /
> >> where?)
> >> >> >> or
> >> >> >> > does the scaling has to happen in a sop and the sleep in the
> dop?
> >> >> >> > Damn, I really thought I was past that initial confusion when
> >> starting
> >> >> >> with
> >> >> >> > Houdini, but  a couple of months off seem to be a full reset on
> my
> >> >> >> brain...
> >> >> >> >
> >> >> >> > Thanks,
> >> >> >> > Thomas
> >> >> >> > _______________________________________________
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> >> >> >> >
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