[Sidefx-houdini-list] lines from point positions

Ron Schab ron.schab at gmail.com
Thu Oct 6 13:17:30 EDT 2016


Hey Garry,

glad it was what u are after.

The way it works I would describe it as:
Width is just a point attribute that mantra "automatically" understands as
a "thickness" value when rendering curves.
It is set on a per point (on the curve) basis and interpolated in between
those points.

So, if  for example you give each point on your curve a random "width"
value the curve should be rendered with varying width along it.

As a quick test and for illustration purposes you could:
- drop down a line-sop and give it let's say 10points.
- then drop down a point-vop-sop after that, dive in, plug ptnum into a
fitrange-vop and set "maximum value in source range" on that fitrange to 10
(to keep it procedural you could channel reference "Points" from your line
sop after promoting that parameter)

=>That should give u a funnel like line with a thickness/width starting
from 0 and going to 1.

In your point-vop-sop you could plug in a ramp-parameter-vop after your
fit-range-vop, chose spline ramp in order to get an adjustable & visual
representation of the shape that will be rendered on your point-vop-sop.

With that in mind you should be able to get any desired width-shape for
your curves.

Hope this clarifies things a bit more :)?


cheers
Ron

Ron Schab
-----------------------------------------------------------------------

http://www.ronthedon.com


On Thu, Oct 6, 2016 at 6:53 PM, Gary Jaeger <gary at corestudio.com> wrote:

> Thanks Ron. That works, but I’m not sure the advantage. But to be clear,
> I’m sure I’m doing it wrong. That’s pretty my my mantra(!) while learning
> houdini,
>
> So at the end of my network, I put and Attribute Create node. Name is
> width and I can set it to get my lines. It’s the randomizing part that’s
> throwing me. Do I then create an Randomize Attribute? Or an wrangle? If I
> set up a randomize, depending on settings I get something that looks like a
> fuzzy line but I can’t seem to get the widths of various lines to be
> randomized. I’m not looking for random along length. Yet. But simply to set
> a range like rand(.1,.5) or whatever.
>
> thanks again.
>
> Gary Jaeger / 650.728.7957 direct / 415.518.1419 mobile
> http://corestudio.com <http://corestudio.com/>
> > On Oct 6, 2016, at 2:14 AM, Ron Schab <ron.schab at gmail.com> wrote:
> >
> > Hey Gary,
> >
> > not having looked at your scene ....
> >
> > I am assuming when you are trying to use pscale for "the weight of the
> > lines as they render" you are trying to set their width/thickness?
> >
> > If so, try using f at width instead for lines :)
> >
> > cheers
> > Ron
> >
> >
> >
> > Ron Schab
> > -----------------------------------------------------------------------
> >
> > http://www.ronthedon.com <http://www.ronthedon.com/>
> >
> >
> > On Thu, Oct 6, 2016 at 12:44 AM, Gary Jaeger <gary at corestudio.com
> <mailto:gary at corestudio.com>> wrote:
> >
> >> Thanks Neil. This works well, except I couldn’t get it working using
> >> Custom Discrete. Messing around I got it basically working using Uniform
> >> (Discrete) and fiddling with the random seed. Still seems to favor one
> of
> >> the colors, but that might be ok. I’d like to understand why though.
> >>
> >> In a similar vein, I’ve been trying to randomize the weight of the lines
> >> as they render. I put an Attribute Create at the end of the chain, and I
> >> can set a value there. Putting an Attribute Randomize after that with
> >> attribute name set to pscale doesn’t seem to do it. Is it because
> they’ve
> >> already been created?
> >>
> >> Ha, things are (slowly) sinking in…
> >>
> >> in case you’re curious the masterpiece is here
> https://www.dropbox.com/s/
> >> ra4walh9qqd99be/1676_FX2_v002.hip?dl=0
> >>
> >> Gary Jaeger / 650.728.7957 direct / 415.518.1419 mobile
> >> http://corestudio.com <http://corestudio.com/> <http://corestudio.com/
> <http://corestudio.com/>>
> >>> On Oct 5, 2016, at 10:41 AM, Neil Dickson <ndickson at sidefx.com> wrote:
> >>> For the picking from 3 colours randomly, a way to do it, though others
> >>> probably have better ways for specific situations, is to use Attribute
> >>> Randomize with Attribute Name set to colour_choice, Distribution set to
> >>> Custom Discrete, 3 values, set to 0, 1, and 2, (this just lets you
> easily
> >>> adjust the relative proportions of each colour), then in an Attribute
> >>> Wrangle:
> >>>
> >>> if (@colour_choice == 0) {
> >>>   @Cd = chv("colour0");
> >>> }
> >>> else if (@colour_choice == 1) {
> >>>   @Cd = chv("colour1");
> >>> }
> >>> else { // @colour_choice == 2
> >>>   @Cd = chv("colour2");
> >>> }
> >>>
> >>> You can press the "Create spare parameters..." button next to the
> >>> VEXpression to create the parameters for the colours and adjust those
> to
> >>> set the colours.  To have attributes, including Cd, copied from the
> >>> template points to the copies, turn on Use Template Point Attributes in
> >> the
> >>> Attribute tab of the Copy SOP.
> >>>
> >>> Cheers,
> >>> Neil
> >>
> >> _______________________________________________
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