Maya Particles

[Guest xionmark]

Hi there,

I'm trying build a POP net to mimick what Maya does for a "goal based particle system" (or it's called something like that).

I've looked over the posts related to this on the forums and tutorials but haven't got it to work like it does in Maya in regards to the particles following the object from which it's birthed and ending up on the object at specific locations (as determind by some attribute such as UV coords on the object).

http://odforce.net/forum/index.php?showtop...particles++goal

It seems like the Creep POP is what I want to use but now I'm not sure because of a few reasons: 1) I can't seem to get the particles to "lag" behind the object after it moves and then have the particles catch up to the object and 2) to have the particles end up at specific locations on the object once the object comes to rest.

I'm think this is going to invlove more POPS than just a simple Creep, but I've haven't been successful yet.

I saw someone do this in Maya in a matter of minutes, surely Houdini can do this too; I would be *bummed* if Maya could do this faster than Houdini.

Suggestions?

--Mark

[jclark]

hey mark,

it sounds like the Attractor pop maybe what your looking for. You can birth off of a surface and than use the surface in the Attractor pop. Make sure that Attractor Use is set to "Single point per particle." This sets up a relationship between the particles and the actual points that birthed them.

Then it's a matter of creating forces at the SOP level w/ the point Sop and playing w/ forces in POPs. I believe there's even a stop at attractor option in the pop

cheers,

-j

[pbowmar]

Follow POP, maybe?

[Guest xionmark]

Follow POP, maybe?

17514[/snapback]

Hi Peter!

I'm pretty sure I tried that but didn't see a way to have it use parametric attributes (e.g. UV's) to determine the way the particles will follow the object around, but I'll check again.

Thanks!

--Mark

[Jason]

Birth on goal, play backwards?

[Guest xionmark]

Birth on goal, play backwards?

17519[/snapback]

But that would be cheating right ...?

I think I'm over engineering the problem/solution for some reason ... I've tried the Creep, Follow, Attract POPs and am getting interesting effects but can't seem to figure out how to have the parametric attributes (UVs) determine particle direction, velocity, etc.

I need some sleeeeeep ...

Still pondering ...

--Mark

[TheUsualAlex]

Do a blendshape (not the SOP) on pop? I'd imagine mixing that with Spring or Lag CHop might help out a bit with the overshoot?

[edward]

I'm being slow here. What exactly is the effect we're trying to achieve?

[Guest xionmark]

I'm being slow here. What exactly is the effect we're trying to achieve?

17527[/snapback]

Hi Edward,

Here's the description of the procedure in Maya from Bill Watral (EFX TD at Charlex):

1) emit particles from random positions on the surface of an object.

NOTE: the UV positions on the surface that the particle is birthed from

is automatically stored in float array variables called parentU and

parentV

3) set the goal of the particle to the object they were birthed from.

4) write a creation expression that says:

goalU = parentU;

goalV = parentV;

5) set your goalPP (goal weight per particle) with an expression or

texture to whatever you want and the particles will either stick or lag

behind the point on the object they were birthed at.

--Mark

[aracid]

hey xionmark

i know what u mean about being quick in maya, it seems that mel and particles have quiet a bit of power, but its such a mission to get something really nice and controllable.

in terms of ur solution

i created a source pop and sourced it off any obj, then had a creep sop that sourced a moving nurb.

in the creep sop, under Prim U/V

i entered

rand($ID) and rand($ID+23)

then, u just used a

lag CHOP (obviously with the conventional CHOP setup)

with the following expression

under LAG

rand($C)*3

and rand($C)*3

its not really the same as in maya, with having the whole solution in just

goalPP = rand(id)

but it seems to give decent results.

strange thing is that polys i cant get decent results, but with mesh, they're the same as a nurb.

anyways hope this helps.

aracid

[Guest xionmark]

Thanks for the idea but it's not really what I'm after.

I'm currently building a VOP net to try to help me prototype this by importing the attribute, i.e. "uv", and I have it controlling the velocity which is cool but I am stuck at the point of having the particles find their location on the surface based on the attribute.

You see the thing is while it would be nice to show Maya users how to do these kinds of operations in Houdini, my thought was also along the lines of being able to control the attribute (with expressions, CHOPs, etc.) and thus control the birthing position *and* where the particles eventually come to rest on the object.

It's not a high priority, I'll figure it out eventually (probably with a little help from the Houdini community), and I'll post it on the forums if it useful for others.

--Mark