Emit particles from faces with a specified normal Is it possible to only use faces whose normal points in certain directions, for example, only emit particles from faces pointing in the positive z direction. or some other condition, like it must lay in the x-y plane with z the z component within -0.5 to 0.5? It could be done by manual selection and using vertex groups, but that would be quite time consuming. Another solution would be to select vertices that fulfill the condition.
The particle options in Blender are rather limited at the time (they promised to change that in 2015...) so the only solution I can think of is Animation Nodes or Python, delete the particles depending on their start direction.