hellos…

is there any way i can make particles form a particle sop follow a spline?

cheers,

Mark

Yes.
Two main ways. First uses the Attractor POP and the second uses Attribute Transfer POP.

The Attractor POP method requires that you pass the curve geometry through a Point SOP and in the Attractor Folder, add some overall force then add your line forces. Line forces travel in the direction of the vertex order of the curve. Then use an Attractor POP to reference in that Point SOP.

The Attribute Transfer POP method requires normals, velocity, or some other vector traveling in the direction of the curve edges. Download the Tangent SOP from the exchange and pass your curve through that to build the line vectors. Then in POPs, you will need to use an Attractor POP to transfer your attribute to the points.
If you use velocity directly, then you will override the velocity on the points in POPs. If you want to affect the particles, best to use normals or some other attribute then in a velocity POP, do something like $VX + $NX*0.01 and repeat for Y and Z. Modify the expression to get your behaviour.

There's a tutorial here:
http://www.sidefx.com/index.php?option=com_content&task=view&id=944&Itemid=132 [sidefx.com]
Dragos

This is one POP which many of us feel should have been implemented by SESI years ago. It's an elementary tool needed for controlling particles which should be provided by SESI; it's quite amazing that this one has dodged the bullet for so long. I mean there is a Tornado DOP (!) but nothing to flow particles along a spline.

It's not the easiest for a user to build one of these, especially one with acceptable behaviour. If you're doing simple AttribTransfer of forces or use the Attractor POP you often end up with a system where particles fly off around bends or collapse around the core of the spline due to some radial force you need to circumvent this problem. The trick is you need to estimate where you want your particle to be at the next time-step and add the appropriate force to get it there. A system which provides intuitive radius controls and some parm which allows you to control how draconian the force is - with per-point attributes for all controls.

there was also a free cmi tutorial (that I can't find on the site)
basically it used a creep SOP and a skinned curve…

I'll try to find it

spaceboyzero
is there any way i can make particles form a particle sop follow a spline?

If you want to use only the Particle SOP (i.e. you're in Escape) you can use the Point SOP forces, or copy Metaballs on (making sure to align Z down the curve) and use the Force SOP. You're in luck, I'm bored, here's an example, using only Escape components.

Cheers,

Peter B

spaceboyzero
is there any way i can make particles form a particle sop follow a spline?
Mark

You can do this in SOPs - not POPs - by putting an edge force on a curve and then feeding that into the force input of the particle SOP. See attached hscript, put in scripts folder and do:
source parts.txt
…in textport

Cheers

EDIT: Oh - yeah - Like Peter said…