Hello,
So, I'm trying to do something trivial in POPs, but it's baffling me in DOPs. Basically I have a curve in space, and I want a force to run along the curve. In POPs, I'd just copy the metaballs to the curve's points (with the normals pointing down the curve) and use a Force SOP.
How do I achieve this in DOPs? The Magnet Force DOP makes no sense to me (and has no example or useful help, sadly) and the Point Force works OK but how do I get each point on the curve to have a force, picking up the normal's direction from the curve?

Cheers,

Peter B

pbowmar
how do I get each point on the curve to have a force, picking up the normal's direction from the curve?

You could use the Copy Data DOP

For the number of copies you would use npoints(“sopCurve”)
Then in the Point Force DOP you would use the point expression to fetch the position of each point and normal.

Force:
point(“../../pointForces”,stamp(“../copydata1”,“PtNum”,0),“N”,0)
Position:
point(“../../pointForces”,stamp(“../copydata1”,“PtNum”,0),“P”,0)

If you want each point on the curve to only influence objects within a certain radius of that point, I'd suggest a Field Force DOP (which does have a couple of example files on the help card). The approach above will apply forces from all points to all objects. Using the Magnet Force DOP will always create a force along the gradient of the metaball, and so won't let you direct the force along the curve.

An RFE has been added to provide a DOP force that is equivalent to the Attractor POP or the Force input on aParticle SOP.

Mark

Cool, thanks Mark. The ability to use the Metaball + Force SOP would be most welcome, it has 1001 uses in POPs )

Cheers,

Peter B

Wolfwood Thanks for the idea, hadn't thought of that. The Field Force works beautifully for what I want, though, still gotta get my head into “Thinking in DOPs” mode )

Cheers,

Peter B