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

Olivier Jeannel facialdeluxe at gmail.com
Wed Nov 29 04:35:12 EST 2017


You can use "Attribute Create" if you're in sop.
Otherwise in Vop, "Bind Export".
Checking with the Geometry Spreadsheet to insure every attributes are
there, or hit "x" and click a node to create a temporary vizualizer.

2017-11-29 9:29 GMT+01:00 Thomas Volkmann <listmail.3d at gmail.com>:

> Yep, I found merging and then referencing the input to be the most straight
> forward for me. I had the intention to do as much as I can in code, but
> obviously my skills are still limited :)
> But on another note:
> Where would you store some global variables that should be referenced by
> some other objects (eg. a frame number that should act as a trigger)?
> Atm I just have an object that holds an attribute-wrangle which is working
> fine. Just curious on other approaches...
> The Null-OUT workflow will be incorporated, thanks Michael!
>
> cheers,
> Thomas
>
> On Tue, Nov 28, 2017 at 6:39 PM Ciaran Moloney <moloney.ciaran at gmail.com>
> wrote:
>
> > 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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> > > >> >> >
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