Thanks, Matt and Molly.  Very excited to see the kd-tree formulation that Meagan has implemented.  A couple additional questions:

 * Using the chosen SPH kernel (thanks to Bili Dong, we now have cubic, quartic, quintic, wendland2, wendland4, and wendland6), the smoothing is conducted on each cell by looking at all the nearest particles.  This is implemented in the process function on the class VolumeWeightedSmooth in yt/geometry/particle_smooth.pyx

What is the default SPH kernel that is used for deposition?  Is it frontend specific (and if so, where is it defined for each frontend), or do we just use a cubic spline as default?

Also, what value is used for the smoothing length of the particle deposition?  I believe most codes already have a smoothing_length field defined by the simulation.  Looking in VolumeWeightedSmooth, it seems to accept a smoothing_length field for the particles but I don't know if this is the simulation-defined field.  I may be wrong, but it seems to me that using the simulation-defined smoothing_length field is only applicable for the "scatter" deposition method.  I thought "gather" recalculates new smoothing lengths to address the fact that you may try to sample the fluid quantities a large distance away from the nearest particles, who all may have small smoothing lengths because of their proximity to each other.  But I may be mixed up here.


Cameron Hummels
NSF Postdoctoral Fellow
Department of Astronomy
California Institute of Technology