Blender Git Loki

More flexible size options for particle billboards. This adds scale factors for width and height of billboards, relative to the particle size. It's useful when the particle size is primarily used for collision and the like, so the billboard appearance can be adjusted independently. Also allows non-square billboards.
In addition the billboards can be scaled by the particle velocity with optional head and tail factors (similar to line drawing options). This allows for pseudo-motionblur effects.