I’ve used this trick Bug: point-sprite particles in GUI - #4 by InShadow and it works!
One more thing: the rendering is “AlphaAdditive”, but instead I’d like it to be “Alpha” mode… I’ve tried setting it with
getAdditionalRenderState().setBlendMode(RenderState.BlendMode.Alpha);
But it doesn’t work. I’ve even changed these but didn’t help: