Im stumbled on what I think must be a super simple setup, I do seem to make it way more complicated than I think it need to be. What I want to create is a saturn ring with asteroid particles. The ones closest to the middle I want to rotate faster (easy by scale it by distance). Thats basically all I want to do. However I thought that aligning the direction to the centre, and just do a velocity on the X would to the trick, so the particles keeps poiting towards the middle and just moves on X in their local axis, however everything moves as on unit, just in one direction when Im doing that. This is what I've done now. Its messy, and the particles tends to move away from the center as I increase the velocity, and I have a null to drag them back.. Simply not a nice solution. Anyone know of a "cleaner" way to achieve the same thing?

did you see this?

http://www.mootzoid.com/html/XsiCorner/emNewton.html

Yes.. I've looked at Newton, but that is even more complicated than my needs just now.

I thought emitting particles, set a billboard Orientation compound towards the null in the centre, and then move the particles in their local X-axis would do the trick. But they doesnt move at all in a circle. So the problem is.. How do I move a particle in their local X?

Take a look here for a compound that moves a particle in its local axis:

http://dot3d.blogspot.com/2009/10/softimage-ice-tree-building-step-by.html

Hi!

Don´t use forces for this, just set the velocity directions and speed of your particles depending on the distance to the center...

Edit: just did a test an noticed, that it leads to the same problem..of course, the tangents alone can´t solve the problem. There has always to be a force/velocity directing to the center of the rotation to keep the particles on track...

Well, but increasing the subsampling helps to dampen this problem...I´ve set it to 20 an the sim keeps "stable" for 1000 frames..

cheers,
oli

Here is the setup. The more you increase the subsampling, the better it works

Cheers,
oli

Thank you Oli! I will test your setup! It looks cleaner by far

...or just use the "Orbit Around Controller" compound...that works precise because it does not rely on tangents which are always approximations and therefor not precise ...

cheers,
oli

The Orbit place everything in the same distance from the centre. Thus not making any "Saturn" rings :/

Here is another version. It is a bit more complicated, but twice as fast:





It uses a parametrical circle for each point (offset with a random number) and then selects the position from this array.