Returns
FXParticle with the given index in the given subgroup. Returns nullptr if particle does not exist.

Parameters
long index:
The particle index. Should be between 0 and GetParticleCount

ParticleFactoryTypes subgroup:
The subgroup type to retrieve the particle from

Returns
FXParticle that has been added. Returns nullptr if something went wrong.

Parameters
ParticleFactoryTypes subgroup:
The subgroup type to add the particle to

Returns
The amount of particles available in the subgroup

Parameters
ParticleFactoryTypes subgroup:
The subgroup type to check the particle count for

Whenever you change a particle group (for example if you change a position of a particle or if you add a particle) you should call UpdateBounds.

Returns
none

Parameters
const ParticleFactoryTypes:
The subgroup type

const vector3d& global_position:
The physical positon to find particle neighbors for

const double radius:
The maximum distance around the physical position to search for neighboring particles. The radius is given in physical space units.

std::vector& neighbors:
Filled with the found neighboring particles

const int cpu:
The cpu thread for the search. Pass if you are in a multiprocessor context.

If you change particles' position in the given subgroup of this particle group you should update the internal search algorithm by calling SetDirtySearch

Parameters
const ParticleFactoryTypes:
The subgroup type to update the searcher for.

Returns
true if the given subgroup is cached. This is not the same as FXBase::IsCached.

Parameters
const ParticleFactoryTypes:
The subgroup type to check the cached state for.