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

Thomas Volkmann listmail.3d at gmail.com
Wed Nov 29 10:25:11 EST 2017


Thanks Olivier, I think I stumbled upon that video during a former Houdini
project. Definitely makes the SI to Houdini transition easier...
But now to the latest problem....
I want to replace the rigidbodies with some other object after the
simulation.
So I merge the sim-object, use "add" to delete the geo and just keep the
points (very intuitive) and then I want to use a "copy to points" node.
By default everything goes haywire, but when I disable "transform using
point orientations" hte objects end up in the right positions but have a
static rotation.
I guess I have to get the intrinsic transforms and apply them to the point
orientation (or similar) before the copy, but I really can't figure it out
atm....
Any ideas?

On Wed, Nov 29, 2017 at 10:44 AM Olivier Jeannel <facialdeluxe at gmail.com>
wrote:

> If triggers for sims is you're thing, I enjoyed this tut :
>
> http://shortandsweet3d.blogspot.fr/2017/01/xsi-to-houdini-4-from-states-to-streams.html
> If you're in pop or dop and want to play it like in ice State
> Machine, Mikael Pettersén nailed it.
>
> 2017-11-29 10:35 GMT+01:00 Olivier Jeannel <facialdeluxe at gmail.com>:
>
> > 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
> >> > > >> >> >> > _______________________________________________
> >> > > >> >> >> > Sidefx-houdini-list mailing list
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> >> > > houdini-list
> >> > > >> >> >> >
> >> > > >> >> >> _______________________________________________
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> >> > > >> >> >>
> >> > https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >> > > >> >> >>
> >> > > >> >> >
> >> > > >> >> _______________________________________________
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> >> -list
> >> > > >> >>
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