$NPT not working inside popnet (new) for impulse count?

[juangea]

Hi all.

 

I'm following a Peter Quint tutorial, the Fluid transform I, and I understood everything, he uses the old Popnet (because the Houdini version presume) and I think I can translate everything to it, but I'm trying to use the $NPT variable for Impulse count so the source can generate same number of particles as points are generated in the source geometry, but it's giving me this error: "Error cooking SOP"

 

This happens when I use as Emission Type "Scatter onto surfaces", Emission activation is "$FF == 1" and Impulse count "$NPT", if I use Emission Type as "Points" there is no error but there are no particles either, if I use "All Points" there are the correct number of particles because it generates 1 particle per point but I cannot define any expression in Impulse Count (it's greyed out) and if I use "All Geometry" it's the same thing.

 

What am I doing wrong?

 

I'm using Houdini 15, I think I remember there was some change regarding calling variables in Houdini 15, but I'm not sure, so maybe $NPT is not available as is anymore.

 

Some ideas?

 

Thanks in advance!

 

Cheers.

 

 

[juangea]

From what I saw in the other thread regarding SOP's. it should be something similar to @NPT or @PT.amount or something similar, but I don't know where to consult this in the help file.

 

Ideas?

 

Thanks!

[loopyllama]

Impulse Activation:

$FF==1

Impulse Count:

npoints("/obj/torus_object1/torus1")

then you can set Emission Type to whatever you'd like.

 

better Impulse Activation is:

$SF==1

this means you emit particles when the simulation frame is 1. If you set Start Frame on the Dop Network to 10, $FF == 1 won't ever activate the sim, where $SF == 1 will emit particles on frame 10, since that is the first simulation frame.

[juangea]

That is cool to know (The SF thing I mean, and the npoints thing too

 

But then I have two questions:

 

1.- it's $NPT variable not working anymore?

2.- How can I use the "first context geometry" option instead to having to make a direct reference to the object itself? I ask this because in this case I will lost the ability to dynamically change the geometry without having to re-link the path.

 

Anyway thanks for the help, I'll keep going with your advice by now

 

Cheers!

[Netvudu]

1- the $NPT variable does still work where it did before H15, even though the suggested workflow now is @numpt which is the VEX syntax and is consistent with using VEX anywhere else.

The reason you cannot make it work being before H13, there was and old POP workflow which was used in a separate context (BTW, it still does exist. You can call it with the TAB menu as POP Network-Old) and it accepted many of Hscript standard variables.

As of H13, SESI added a new particle workflow which moved particles to DOPs instead of having their own context. As with many other changes recently, this made the system more powerful and faster and generally speaking "better", but harder to learn.

If you have played around DOPs for a while you probably know by now that standard variables for SOPs usually don´t work in DOPs, as this context is a very different animal.

 

2- if you create your own DOP Network from SOPs, let´s say inside, for instance, a geometry node, you will see it has several inputs so that you can use those context geometry entries.

BUT, even if you don´t use those, it doesn´t mean you cannot change your geometry dynamically. Just point your path to a SOP null (we usually call it something similar to "OUT") and whatever you connect to that null node, be it directly or indirectly through an Object Merge, it will become your particle source geometry.

Edited February 5, 2016 by Netvudu

[juangea]

Got it!

 

Thanks to you both

 

Cheers!