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

Thomas Volkmann listmail.3d at gmail.com
Wed Nov 29 03:29:25 EST 2017


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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