Actually, you cannot change the position of a shape sample at evolve.
But as a workaround you can :
- Pass the position to the Fx with a float3 attribute AttractorAttributePosition.
- Create a new field AttractorPosition
- In an Evolver script (before the attractor Evolver) : AttractorPosition = Position - AttractorAttributePosition;
- In the Attractor Evolver, enter AttractorPosition in "Field customization / PositionField"
Unfortunately, this will not work for rotations. To do so you will have to compute the inverse transformation (translation/rotation) to replace your particles in the local space of your attractor.
Hopes this helps!