[Sidefx-houdini-list] Prim intrinsic in CHOP

Matt Ebb matt at mke3.net
Thu May 18 18:10:31 EDT 2017


So many people are surprised when they learn about that intrinsic, it can
be extremely helpful, and takes away some of the pain when dealing with
packed prims transformations (multiple different inconsistent matrices,
setting P point attribute, etc).

I think it would be handy to have a checkbox in the Pack/File SOP that
turns on that intrinsic for newly created packed primitives - eg. "Use
Instance Transform Point Attributes" or something...

On 18 May 2017 at 04:47, Neil Dickson <ndickson at sidefx.com> wrote:

> Feel free to submit an RFE for "intrinsic:transform" to be supported, with
> an example HIP file showing the situation you'd like it to be supported
> in.  It works in a few places, e.g. the prim, prims, detail, and details
> expression functions, as well as the primattrib VEX function, should
> support reading intrinsics with "intrinsic:nameoftheintrinsic" in place of
> an attribute name.
>
> Putting this in an Attribute Wrangle with Run Over set to Primitives seems
> to enable the use of transformation attributes for packed primitive
> transforms:
> setprimintrinsic(geoself(),"pointinstancetransform", at primnum,1);
>
> Cheers,
> Neil
>
> On Wed, May 17, 2017 at 2:29 PM, Olivier Jeannel <facialdeluxe at gmail.com>
> wrote:
>
> > Hey Neil,
> > "intrinsic:transform" doesn't seem to be recognized either. (but possibly
> > I'm doing it wrong)
> >
> > How do you set the pointinstancetransform intrinsic on the primitives to
> 1
> > ?
> > Wrangle ?
> > Do you have any doc or example ?
> >
> > Thank you :)
> >
> >
> >
> > 2017-05-17 19:16 GMT+02:00 Neil Dickson <ndickson at sidefx.com>:
> >
> > > I don't know which CHOP you're talking about, (since I'm not very
> > familiar
> > > with CHOPs either), but does specifying the name "intrinsic:transform"
> > > work?  If not, could you submit an RFE for it with an example HIP file?
> > >
> > > Also, there's an option for packed primitives to automatically use the
> > > transformation attributes that the Copy to Points SOP and other SOPs
> use,
> > > like P, N, up, pscale, pivot, orient, rot, scale, xform, etc, so you
> > might
> > > be able to use those.  You'll have to first set the
> > pointinstancetransform
> > > intrinsic on the primitives to 1.
> > >
> > > Cheers,
> > > Neil
> > >
> > > On Wed, May 17, 2017 at 12:17 PM, Olivier Jeannel <
> > facialdeluxe at gmail.com>
> > > wrote:
> > >
> > > > Hi,
> > > >
> > > > I rarely use CHOP.
> > > > The only use I found (that was explained to me by my friend Jerome
> > > > Pastorello) is to use a CHOP network to add some Jiggle on the
> Position
> > > and
> > > > on the Orient of some already animated points.
> > > >
> > > > Basicly the CHOP nicely overshoots the P and Orient, resulting in a
> > > > pleasant "boing" effect.
> > > >
> > > > Now I'm working with some packed primitives.
> > > > I animate them directly in vop by setting their Intrinsic transform
> > > > attribute (rotation and position in a matrix)
> > > >
> > > > My deepest wish would be to apply this CHOP effect to the intrinsic
> > > > transform (matrix).
> > > > But since this attribute is a Primitive, is this possible ?
> > > > If it is possible, what is the name of the attribute in the CHOP ?
> > > > "transform" doesn't seem to be accepted.
> > > >
> > > > Thank you :)
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