[Sidefx-houdini-list] Does $CH works in CHOPs?

mdunkley at gmail.com mdunkley at gmail.com
Wed Sep 7 14:02:02 EDT 2011


Hi Pablo -

Perhaps I'm misunderstanding the issue, but have you taken a look at the  
foreach chop? At its most basic, it will strip down your channels based on  
the channel indices you're talking about to let you work on everything that  
has the same index at once ( ie tx45 ty 45 tz 45 rx45 vx45, etc ), and give  
you channel ref access to the index number that you can use for randomness  
or anything else. So long as "organize by attribute" is set up in your geo  
chop, then those channel index numbers will correlate to the attribute  
you're organizing by.

hope that helps,
mike

On , Pablo Giménez <pablogipi at gmail.com> wrote:
> Thanks Francois.

> I have tried using the Expression Chop, but the problem is that $C returns

> the index of the channel.

> I am not interested in the channel index I am interested in the point  
> index

> that this channel belongs to.

> For instance if you have lots of transforms channel, a transform for a  
> point

> is: tx45 ty45 tz45

> the indexes for these channels could be anything, but the point is 45, I

> need to get this point index which is contained in the name.

> Or get a unique number for all t[xyz]45 channels, so I can apply the same

> randomness to all of them.

> If you know know you have 3 channels per point something like $C % ($NC /  
> 3)

> could do the job.

> I think is just a workaround.

> What would be great will be to be able to apply an operation to a set of

> channels that belongs to the same point. Noise or Jiggle already do this I

> think. But would be nice to do it in all CHOPs.





> 2011/9/7 François Duchesneau sidefx at trinix.ca>



> > I think what you need is to use an Expression Chop and use the many

> > available expressions like ioc() etc and their variables like $C, $I.

> >

> > You can manipulate any data this way. Have a look at Vop Chop too.

> >

> > Hope this help.

> >

> > François

> >

> >

> > Pablo Giménez wrote:

> >

> >> Hi All.

> >> I a mtrying to get modify some chopd to get variations based on point  
> id.

> >> For instance in a jiggle chop you use channels t[xyz]$PT.

> >> What I want to do is to extract the point id string and get a random

> >> number

> >> from it to modify the jiggle per point.

> >> In the help says $CH return the name of the current channel:

> >>  
> http://www.sidefx.com/docs/**houdini11.0/expressions/_**globalshttp://www.sidefx.com/docs/houdini11.0/expressions/_globals>

> >> But trying something like:

> >> atof(strreplace($CH, "tx", ""))

> >> Doesnt work alway returns zero.

> >> Any idea how to do something like this?

> >> Thanks!

> >>

> >>

> >>

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> --

> Un saludo

> Best Regards

> Pablo Giménez

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