The sphere mats here are made in the function editor of course and the alpha plane objects are particle freeze frames from Particle Illusion and Texturemaker masked out really nice and tweaked up. I use Fluid Mask which is the most awesome masking and transparency tweaking tool ever!!

Since illusion is the name of our 3d game, all of the materials have shadows turned off and luminosity up. With the spheres, if you have two side by side and they intersect, you sometimes will see that seam even if super fuzzy. So receding and properly scaled placement allows all the edges to blend nicely.