I'm using Unity 3.5.5f3 wich has the Shuriken particle system.

I've made a blood particle system based on Unity's demos. (Exploding paint [Blood]) The blood is flowing and when it collides with a Plane Transform wich I've created a small pool of blood spawns as a Collision Sub Emitter.

My main problem is that when I want to add another object to collide it just doesn't want to work. When I create a cube, and set it as a collision plane the collision will only occur at the half of the cube.

I want this to happen: When it reaches the cube's surface the sub emmiter activates, and when the surface is horizontal it appears horizontally, and if it's vertical then vertically. Now it just appears horizontally everytime like in the picture.

How could I solve it?